:Crusading movement

The Crusades are commonly defined as religious wars waged by Western European warriors during the Middle Ages for the holy city of Jerusalem in Palestine.{{sfn|Hornby|2005|p=370}}{{sfn|Nicholson|2004|p=xlviii}} However, their geographical scope, chronological boundaries, and underlying motivations are fluid in academic studies.{{sfn|Jotischky|2017|pp=10–11}}{{sfn|Nicholson|2004|pp=xl–xli, xlviii}} The crusading movement fostered distinctive institutions and ideologies, exerting a heavy influence on medieval societies not only in Catholic Europe but also in neighbouring regions.{{sfn|Murray|2006|p=xxxi}}{{sfn|Lloyd|2002|p=65}}

File:BritLibRoyal5DVIIFolio067r.JPG of The City of God by Augustine]]

In classical antiquity, Greek philosophers and Roman jurists developed just war theories that would later shape crusading theology. Aristotle emphasised just end, stating that "war must be for the sake of peace". Roman legal tradition required a {{Transliteration|la|casus belli}}—just cause—and held that only legitimate authorities could declare war; defensive actions, restitution of property, and punitive measures were among the acceptable grounds for warring.{{sfn|Tyerman|2019|pp=13–14}}

Although the Bible—the central Christian scripture—contains conflicting views on violence,{{refn|group=note|The Old Testament portrays the Israelites' struggles against their enemies as godly sanctioned wars but also mentions that God's Fifth Commandment prohibits homicide; in the New Testament, Jesus says that "all who take the sword will perish by the sword", but also states that he has "not come to bring peace, but a sword".{{sfn|Asbridge|2012|pp=14–15}}}}{{sfn|Jaspert|2006|p=14}} the Christianisation of the Roman Empire in the {{nowrap|4th century}} prompted Christian interpretations of just war. Ambrose, a former imperial official turned bishop, was the first to equate enemies of the state with enemies of the Church.{{sfn|Tyerman|2019|p=14}}{{sfn|Madden|2013|p=2}}

The empire was divided into two parts in 395.{{sfn|Lock|2006|p=358}} Fifteen years later, the sack of the city of Rome by the Visigoths inspired Ambrose's student Augustine to write The City of God, a monumental historical study.{{sfn|Backman|2022|pp=56–59}} In it, Augustine argued that the biblical prohibition on killing did not apply to wars waged with divine approval.{{sfn|Tyerman|2019|p=15}} For him, a war must be declared by legitimate authority, pursued for just causes after peaceful alternatives had failed, and conducted with restrained force and good intent; just causes included self-defence, the enforcement of justice, and recovery of stolen property.{{sfn|Tyerman|2019|p=14}}{{sfn|Jaspert|2006|p=15}} However, his scattered statements about warfare were nearly forgotten after the fall of the Western Roman Empire in 476.{{sfn|Tyerman|2019|p=14}}{{sfn|Jaspert|2006|pp=14–15}}

From the ruins of the Western Roman Empire, new Christian kingdoms emerged, largely ruled by Germanic warlords. For this new aristocracy, fight and comradeship were core social values. Their violent acts were often praised by clergy seeking patronage.{{sfn|Tyerman|2007|pp=35–36}} Yet the Church still regarded homicide as a sin, and those who killed in battle were expected to do penance—typically fasting{{sfn|Thomson|1998|pp=69–70}}—to obtain absolution.{{sfn|Jaspert|2006|pp=14, 30–31}}

Meanwhile, the Eastern Roman (Byzantine) Empire endured, though much of its territory, including Palestine, was conquered by the rapidly expanding Islamic Caliphate by the {{nowrap|mid-7th century}}.{{sfn|Backman|2022|pp=126, 141–143}}{{sfn|Lock|2006|p=4}} Islam's holiest text,{{sfn|Backman|2022|pp=137–138}} the Quran contains several verses on {{Transliteration|ar|jihad}}—struggle to spread and defend the faith.{{refn|group=note|Both the {{Transliteration|ar|jihad}} and the crusades are holy wars, but nothing proves that they were connected in any way. The historian Paul M. Cobb attributes their similar features to "their common roots in a universal monotheism whose God is a jealous god".{{sfn|Cobb|2016|p=29}}}}{{sfn|Hillenbrand|2018|pp=89–91}}{{sfn|Jaspert|2006|p=75}} In the early {{nowrap|8th century}}, Muslim forces crossed into Europe, conquering much of the Iberian Peninsula.{{sfn|Backman|2022|p=144}}{{sfn|Lock|2006|p=6}} Christians living under Muslim rule were not forced to convert but had to pay a special tax, the {{Transliteration|ar|jizya}}.{{sfn|Cobb|2016|p=30}} As Muslim conquests stabilised, a threefold civilisational order emerged from the old Roman world: the turbulent and fragmented Western Europe, the diminished Byzantine state, and the offensive Islamic world.{{sfn|Backman|2022|pp=144–146}}

Christian resistance to Muslim expansion led to the formation of the small Kingdom of Asturias in northwestern Iberia. Within a century, the resistance evolved into an expansionist movement, seen by the natives as divinely sanctioned—a mission to reclaim lost Christian lands. The {{nowrap|9th century}} brought repeated invasions by non-Christian groups across Western Europe, reviving the notion of holy war.{{sfn|Jaspert|2006|p=15}} In 846, Pope Leo IV promised salvation on God's behalf to those who died defending the Patrimony of Saint Peter, the papal territories in Central Italy.{{sfn|Tyerman|2007|p=38}}{{sfn|Bysted|2014|pp=53–54}}

As warfare became a near-constant reality, a new military class of mounted warriors emerged. Referred to as {{Transliteration|la|milites}} in contemporary texts, they were skilled in specialised weapons like the heavy lance.{{sfn|Jaspert|2006|p=16}}{{sfn|Bull|2002|p=24}} To curb their violence, church leaders initiated the Peace of God movement, threatening excommunication for transgressors.{{sfn|Backman|2022|pp=213–214}}{{sfn|Jaspert|2006|pp=17–18}} Quite oddly, this effort to reduce bloodshed also militarised the Church, as bishops increasingly had to raise armies to enforce the Peace.{{sfn|Morris|2001|p=144}}

File:Rotunda, Adomanan de locis santis.jpg in an early-9th-century manuscript of {{Transliteration|la|De locis sanctis}} ('About Sacred Places'), a work by the Irish monk Adomnán]]

In the absence of strong central authority, regional strongmen took control of parishes and abbeys, often installing unfit candidates in ecclesiastical roles. Believers feared these irregular appointments jeopardised the validity of sacraments,{{sfn|Backman|2022|pp=214–215}}{{sfn|Jaspert|2006|p=25}} and anxiety about afterlife punishments intensified.{{sfn|Thomson|1998|pp=69–70}}{{sfn|Jaspert|2006|pp=30–31}} Sinners were expected to confess and perform acts of penance before being reconciled with the Church. As penance could be burdensome, priests began offering indulgences {{circa|1030}}, commuting such duties into acts of piety like almsgiving or pilgrimage.{{sfn|Mayer|2009|pp=25–27}}{{sfn|Bysted|2014|p=20, 96}} Among these, penitential pilgrimages to Palestine held special spiritual value, as the region was the setting of the ministry of Jesus Christ.{{sfn|Cobb|2016|pp=33–34}}{{sfn|Jaspert|2006|pp=21–22}} The Church of the Holy Sepulchre in Jerusalem—believed to mark Jesus's crucifixion and resurrection—became the most revered destination.{{sfn|Tyerman|2019|pp=xxiii–xxv}}{{sfn|Jotischky|2017|pp=34–36}}

{{Main|Cluniac Reform|Gregorian Reform}}

{{Further|History of the papacy (1048–1257)}}

The widespread fear of damnation induced a series of reform movements within the Church, many initiated by affluent monasteries. Cluny Abbey set a decisive precedent in 910, when its foundation charter guaranteed the monks the right to freely elect their abbot. The Cluniac Reform spread rapidly, gaining support from aristocrats who valued the monks' prayers for their souls.{{sfn|Thomson|1998|pp=33–35}}{{sfn|Jaspert|2006|pp=27–28}} The Cluniac houses answered solely to papal authority.{{sfn|Jaspert|2006|p=27}}{{sfn|Latham|2011|p=231}}

The popes, regarded as the successors of Peter the Apostle, claimed supremacy over the entire Church, citing Jesus's praise for Peter.{{sfn|Thomson|1998|p=39}} In reality, however, Roman noble families controlled the papacy until Holy Roman Emperor Henry III seized Rome in 1053. He appointed reform-minded clerics who promoted the so-called Gregorian Reform advocating the "liberty of the church". This movement outlawed simony—the buying and selling of church offices—and gave high-ranking clerics known as cardinals exclusive right to elect the pope.{{sfn|Thomson|1998|pp=82–85}}{{sfn|Jotischky|2017|p=25}} Andrew Latham, a scholar of international relations, notes that the reformist popes redefined the Church's identity, placing it in structural conflict with "a range of social forces within and beyond Christendom".{{sfn|Latham|2011|p=240}} By then, differences in theology and liturgy between the western and eastern branches of mainstream Christianity had become more pronounced.{{refn|group=note|The unilateral modification of the Nicaean Creed by Western clerics, and the use of leavened or unleavened bread during the Eucharist (a central element of Christian liturgy) were the most evident differences between the two Christian communities.{{sfn|Jaspert|2006|p=4}}}} The resulting tensions led to mutual excommunications in 1054, and the eventual split into the western Roman Catholic and eastern Orthodox Churches, though communion was not entirely severed.{{sfn|Jaspert|2006|p=4}}{{sfn|Jotischky|2017|pp=28–29}}

A spiritual revival also took root. New monastic communities like the Carthusians and Cistercians emerged, and the Rule of Saint Augustine spread among secular clergy. This period saw a rise in Christocentrism, a focus on Christ's life and sufferings, also inspiring a wave of wandering preachers, many of whom defied episcopal authority.{{sfn|Jaspert|2006|p=29}}

{{See also|Medieval Warm Period}}

File:1071 CE, Europe.svg]]

Four major powers dominated the Mediterranean world {{circa|1000}}: the Umayyads in Al-Andalus (Muslim Spain), the Fatimids in Egypt, the Abbasids in the Middle East (at least in theory), and the Byzantine Empire. Within a few decades, all experienced serious calamities—especially in the east, where climate anomalies triggered famine and instability.{{sfn|Tyerman|2019|pp=33–41, 47}}{{sfn|Ellenblum|2012|p=3}} In contrast, the climate change benefitted Western Europe, contributing economic and demographic growth.{{sfn|Tyerman|2019|p=47}}

Al-Andalus fragmented into small Muslim states due to internal strife, making them vulnerable to Christian advances—a process known as the {{Transliteration|es|Reconquista}} ('reconquest').{{sfn|Cobb|2016|pp=60–70}} The medievalist Thomas Madden describes the {{Transliteration|es|Reconquista}} as "the training ground for the theological and moral justification of the crusading movement", combining pilgrimage with anti-Muslim warfare.{{refn|group=note|The Iberian shrine of the Apostle James the Great was regularly visited by French warriors. On these occasions, they often joined campaigns against Muslims to regain what they regarded Christ's patrimony.{{sfn|Madden|2013|p=4}}}}{{sfn|Madden|2013|p=4}} In Egypt and Palestine, repeated failures of the Nile's annual flooding led to famine and interreligious tensions flared up. In 1009, the Fatimid caliph Al-Hakim ordered the demolition of the Holy Sepulchre,{{refn|group=note|A papal encyclical, allegedly written by Pope Sergius IV after the destruction of the Holy Sepulchre, claims that Sergius decided to lead a fleet to the east and to rebuild the destroyed church, but it is a late-11th-century forgery, completed in the Moissac Abbey.{{sfn|Mayer|2009|p=17}}}}{{sfn|Ellenblum|2012|pp=46–47}} but it was later rebuilt with Byzantine support.{{sfn|Lock|2006|p=12}} Meanwhile, the influx of Turkic nomads from Central Asia—known as Turkomans— destabilised the Middle East. Their leader Tughril I of the Seljuk clan captured the Abbasids' capital Baghdad in 1055.{{sfn|Ellenblum|2012|pp=61–96}}{{sfn|Lock|2006|pp=12–14}} His successor Alp Arslan routed the Byzantines at Manzikert in 1072, opening Anatolia to Turkoman settlement.{{sfn|Cobb|2016|pp=71–72}}{{sfn|Jotischky|2017|p=45}}

As traditional powers declined, Italian merchants took increasingly control over Mediterranean trade.{{refn|group=note|As early as 1015 or 1016, the Pisans and Genoese destroyed a base of Muslim pirates in the island of Sardinia.{{sfn|Tyerman|2019|p=57}}}}{{sfn|Tyerman|2019|p=57}} At the same time, the Normans from northern France emerged as a dynamic force, conquering southern Italy and the island of Sicily by 1091.{{sfn|Backman|2022|pp=287–288}}{{sfn|Cobb|2016|pp=49–60}} Their ambitions also threatened papal interests, prompting Pope Leo IX to offer absolution to warriors joining his eventually failed campaign against them.{{sfn|Bysted|2014|p=57}}{{sfn|Jotischky|2017|p=26}} The incident indicates the reform papacy's eagerness to invoke spiritual incentives for warfare.{{sfn|Morris|2001|pp=144–145}}

For Western warriors, war offered an opportunity to seize lands, accumulate power or even establish dynasties.{{refn|group=note|The Hautevilles of the Kingdom of Sicily is the most frequently cited example. They descended from a petty Normandian lord Tancred whose 11 sons settled in southern Italy in the {{nowrap|11th century}}.{{sfn|Bartlett|1994|p=49}}}}{{sfn|France|1999|pp=188–189}} These ambitions often aligned with the aims of reformist popes, who offered absolution to participants in campaigns against Muslim states in Sicily and Iberia.{{refn|group=note|Pope Alexander II offered absolution to the Normans attacking Sicily and the remission of sins to unidentified warriors departing to fight in Iberia.{{sfn|Bysted|2014|pp=57–58}}}}{{sfn|Bull|2002|p=18}}{{sfn|Bysted|2014|pp=57–58}} Since these had once been Christian lands, papal attention soon turned to Palestine.{{sfn|Bull|2002|p=19}} Pope Gregory VII planned a campaign to liberate Jerusalem as early as 1074, though this plan never materialised.{{sfn|Tyerman|2007|p=49}} Two years later, debates over the limits of ecclesiastic and secular authority opened the fierce Investiture Controversy.{{sfn|Jotischky|2017|p=25}}{{sfn|Backman|2022|pp=301–302}} These disputes reawakened interest in just war theory. The theologian Anselm of Lucca compiled Augustine's statements about just wars, arguing that war, in some cases, could be a genuine act of love aimed at preventing sin; his fellow Bonizo of Sutri saw those who died in just wars as martyrs of the faith.{{sfn|Jotischky|2017|pp=25–27}}{{sfn|Bysted|2014|p=209}} These concepts shaped the idea of penitential warfare whereby fighting for a just cause could itself serve as penance.{{sfn|Riley-Smith|2002|p=78}}

{{main|Crusades}}

The fusion of classical just war theories, biblical views on warfare, and Augustine’s teaching on legitimate violence provided the Western Church with an ideological framework for engaging in military affairs.{{sfn|Bull|2002|p=18}} By the late {{nowrap|11th century}}, Western Christendom had developed into a union of local churches under papal authority.{{sfn|Bartlett|1994|p=19}} Amid a religious revival, when concern over personal sin peaked, the papacy was well-positioned to exploit the warrior class's social values, particularly loyalty.{{sfn|Jaspert|2006|p=33}}

{{main|First Crusade}}

File:Godefroi1099.jpg during the First Crusade (a miniature from a 14th-century manuscript about the crusades to the Holy Land)]]

Confronted by devastating Turkoman invasions, the Byzantine emperor Alexios I Komnenos appealed to Pope Urban II for help recruiting troops from Western Europe. {{nowrap|Urban II}}, says the historian Thomas Asbridge, recognised this as an opportunity "to reaffirm and expand" papal authority. He convened a church council in Clermont in France, where on 27 November 1095 he called for a military campaign against the Turkomans, offering loosely defined spiritual rewards to those who joined.{{sfn|Asbridge|2012|pp=34–38}}{{sfn|Jotischky|2017|p=54}} The church historian Jonathan Riley-Smith presents Urban's call as a "revolutionary appeal" for associating "warfare with pilgrimage to Jerusalem".{{sfn|Riley-Smith|2002|p=78}}

Urban's appeal sparked unexpected enthusiasm. People from diverse social backgrounds gathered in northwestern Europe, and the first poorly organised groups—some 20,000 to 30,000 crusaders—set out for the east in March 1096. Known as the People's Crusade, this initial movement ended in catastrophe: many died before reaching the Byzantine capital, Constantinople, and most of the survivors were massacred by the Turkomans.{{sfn|Lloyd|2002|pp=35–36}}{{sfn|Lock|2006|pp=20–21}} A second wave, comprising at least 30,000 warriors and as many non-combatants, departed between August and October 1096 under prominent aristocrats such as Raymond of Saint-Gilles, Bohemond of Taranto, and Godfrey of Bouillon.{{sfn|Asbridge|2012|pp=43–46}}{{sfn|Jaspert|2006|pp=40–45}} By then, the Middle East had fragmented into competing states, each ruled by a Seljuk prince, Turkoman or Kurdish warlord, or Arab potentate, which facilitated the crusaders' progress.{{sfn|Irwin|2002|pp=215–217}} They defeated Turkoman forces in Anatolia and Syria, and captured two important cities, Edessa and Antioch, and ultimately seized Jerusalem on 15 July 1099.{{sfn|Lock|2006|pp=20–26}}

The first Crusaders consolidated their conquests into four Crusader states: Edessa, Antioch, Jerusalem, and Tripoli. Their defence inspired further crusades as early as 1101. Several campaigns, particularly those led by kings, are referred to by numbers.{{sfn|Lloyd|2002|p=37}}{{sfn|Lock|2006|pp=137–224}} The fall of Edessa in 1144 to the Turkoman leader Imad al-Din Zengi prompted the next major expedition, the Second Crusade. Despite being led by kings—Louis VII of France and Conrad III of Germany—it failed in 1148.{{sfn|Lock|2006|pp=147–150}}{{sfn|Madden|2013|pp=50–59}}

Zengi's successor, Nur al-Din unified the Syrian Muslim states and dismantled the Fatimid Caliphate. These territories were brought under the control of Saladin, an ambitious Kurdish general. In 1187, he destroyed the Jerusalemite field army at Hattin in 1187, and conquered most Crusader territory, including the city of Jerusalem.{{sfn|Jotischky|2017|pp=119–129}}{{sfn|Asbridge|2012|pp=343–363}} This disaster prompted the Third Crusade led by Emperor Frederick I, Richard I of England and Philip II of France. Though Jerusalem remained under Muslim control, the crusade secured the Crusader states' survival and resulted in the creation of the Kingdom of Cyprus on former Byzantine lands.{{sfn|Lock|2006|pp=151–155}}{{sfn|Madden|2013|pp=77–90}}

The recovery of Jerusalem became the central aim of later crusades, yet the Fourth Crusade was diverted by a Byzantine claimant to Constantinople. The Crusaders sacked the city and established a Latin Empire in the Aegean.{{sfn|Madden|2013|pp=93–114}}{{sfn|Lock|2006|pp=82–87, 156–161}} The Fifth Crusade against Egypt failed between 1217 and 1221. During the Sixth Crusade in 1229, Jerusalem was recovered through negotiations by the excommunicated Emperor Frederick II, but it was sacked in 1244 by Khwarazmian raiders .{{sfn|Lock|2006|pp=106, 167–170}} The loss of Jerusalem spurred Louis IX of France to launch a crusade against Egypt in 1248. However, the Egyptians triumphed, forcing his withdrawal in 1250.{{sfn|Madden|2013|pp=156–155}}

{{Main|Crusades against Christians|Northern Crusades|Reconquista}}

File:Zespół Zamku Krzyżackiego MALBORK 01.jpg of the Teutonic Order in Prussia]]

The historian Simon Lloyd emphasises that "crusading was never necessarily tied" to the Holy Land. As early as 1096, Pope Urban discouraged Catalan nobles from joining the First Crusade, offering the same spiritual rewards for continuing their fight against the Moors (Iberian Muslims).{{sfn|Lloyd|2002|pp=38–39}}{{sfn|O'Callaghan|2003|pp=32–33}} In 1123, the First Lateran Council unequivocally equated anti-Moorish campaigns with crusades for the Holy Land.{{sfn|Madden|2013|p=116}}{{sfn|O'Callaghan|2003|p=38}} The Iberian crusades advanced Christian expansion across the peninsula,{{sfn|Lloyd|2002|p=39}} reducing Al-Andalus to the Emirate of Granada by 1248.{{refn|group=note|In 1095, a new fundamentalist Muslim power, the Almohads inflicted a serious defeat on the Castilian royal army at Alarcos, but the Almohads were routed by a large crusader army at Las Navas de Tolosa in 1213.{{sfn|Madden|2013|p=117}}{{sfn|Lock|2006|pp=80, 90}}}}{{sfn|Madden|2013|p=117}}

Other crusades emerged from conflicts between Christian and non-Christian groups.{{sfn|Lloyd|2002|p=39}} As early as 1107–08, Saxon leaders referred to the land of the Wends (a pagan Slavic people) as "Our Jerusalem"; though the anti-Wendish war was only officially recognised as a crusade in 1147. From then, the northern German, Danish, Swedish and Polish rulers often waged papally-sanctioned campaigns against the pagan Slavic, Baltic and Finnic tribes—collectively termed the Northern Crusades. Leadership of these anti-pagan efforts passed to the Teutonic Order's warrior monks by the 1260s.{{sfn|Jaspert|2006|pp=125–128}}{{sfn|Bartlett|1994|p=262}}

Crusading zeal was also directed at Christian opponents of the papacy. So-called "political crusades" were launched against Emperor {{nowrap|Frederick II}}, his heirs, and disobedient papal vassals.{{refn|group=note|The first crusade waged for political purposes was proclaimed by {{nowrap|Pope Innocent III}} in 1199 against the German aristocrat Markward of Anweiler who had challenged the Pope's claim to regency in Sicily.{{sfn|Lloyd|2002|p=39}}{{sfn|Lock|2006|pp=155–156}}}}{{sfn|Lloyd|2002|pp=39–40}} Heretics—Christians who rejected official Church doctrine—became targets under Pope Innocent III, beginning in 1209.{{sfn|Jaspert|2006|p=135}} Crusades were later proclaimed against the restored Byzantine Empire after Western forces lost Constantinople in 1261.{{sfn|Lock|2006|pp=181–183}}

Between 1250 and 1260, the Mamluks supplanted the Ayyubids—Saladin's relatives—as the dominant Muslim power in the Middle East. They launched systematic campaigns against the Crusader states, massacring Christian populations in conquered areas. {{nowrap|Louis IX}} mounted another crusade, but it ended abruptly with his dead in 1270. Civil war soon factured the Crusader states, and by 1291, the Mamluks had captured the last Frankish strongholds in the Holy Land.{{sfn|Madden|2013|pp=162–175}} Although popes, kings and thinkers continued to propose new crusades to retake Jerusalem,{{refn|group=note|Prominent authors of crusade tractates include James I of Aragon, Charles II of Sicily, the last Templar grand master James of Molay, the French minister William of Nogaret, the Cilician aristocrat Hayton of Corycus, the Franciscan friar Fidentius of Padua, and the mystic Ramon Lull.{{sfn|Tyerman|2019|p=379}}}} efforts were hampered by events like the outbreak of the Hundred Years' War.{{sfn|Jotischky|2017|pp=266–271}}{{sfn|Housley|2002|pp=258–266}}

Despite internal strife in the Christian kingdoms, the {{transliteration|la|Reconquista}} persisted, culminating in the conquest of Granada by the united forces of Castile and Aragon in 1492.{{sfn|Housley|2002|pp=267, 282–283}}{{sfn|O'Callaghan|2003|pp=209–214}} In the early {{nowrap|14th century}}, {{Transliteration|de|Preussenreise}}—sesonal expeditions by Catholic aristocrats to join the Teutonic Knights' campaigns against pagans—became a hallmark of chivalric culture.{{sfn|Jotischky|2017|p=277}} These efforts, which the historian Eric Christiansen calls an "interminable crusade", brought widespread destruction in the Baltic.{{sfn|Christiansen|1997|p=164}}{{sfn|Housley|2002|p=273}} In the western Mediterranean, the papacy often proclaimed crusades against Christian rivals, such as Aragon, Sicily, and rouge mercenary groups. During the Western Schism (1378–1417), with two and later three competing claimants to papacy, the rival popes often called crusades against the other's supporters.{{refn|group=note|At the beginning of the Western Schism, Urban VI (who had his seat in Rome) and Clement VII (who settled in Avignon) were competing for the papal throne. Urban granted crusading privileges to the warlike English bishop Henry le Despenser to attack the Flemish who supported Clement, and also to the English duke John of Gaunt to take up arms against the clementist John I of Castile.{{sfn|Tyerman|2007|pp=900–901}}}}{{sfn|Housley|2002|p=268}}{{sfn|Lock|2006|pp=198–199}} The Hussite Wars reignited anti-heretical crusading in 1420, though Hussitism endured in Bohemia.{{sfn|Housley|2002|pp=280–282}}{{sfn|Nicholson|2004|pp=65–74}}

Extensive piracy in the Mediterranean revived anti-Muslim crusading in the {{nowrap|mid-14th century}}.{{refn|group=note|The Aydinids' Anatolian lordship was targeted by three crusades between 1333 and 1347.{{sfn|Tyerman|2019|p=397}}}}{{sfn|Tyerman|2019|pp=396–397}} Major international campaigns were launched against the rising Ottoman Empire, but could not prevent the Ottoman conquest of Constantinople in 1453.{{sfn|Tyerman|2019|pp=397, 403–410}} Although the Reformation curtailed papal authority, the papacy continued advocate anti-Ottoman crusades, helping to forge coalitions such as the Holy League even into the late {{nowrap|17th century}}.{{sfn|Nicholson|2004|pp=77–88}}{{sfn|Housley|2002|p=290}}

Pope {{nowrap|Urban II's}} appeal at Clermont introduced a remarkably novel concept for most attendees.{{sfn|Tyerman|2011|pp=22–23}} Though Western Christians had embraced the idea of divinely-sanctioned warfare against the enemies of their faith, theologians and jurists still considered it a subject requiring further reflection.{{sfn|Nicholson|2004|p=5}} While Urban underlined the military nature of the expedition, his agents largely portrayed it as a pilgrimage.{{sfn|Tyerman|2011|p=22}}

Contemporaries saw the First Crusade as a singular event, the result of God's direct intervention. However, as the movement expanded, divine intervention no longer sufficed as a rationale. Canon lawyers required a clear framework that also reinforced papal authority.{{sfn|Tyerman|2011|pp=23–24}} The {{Transliteration|la|Decretum Gratiani}}, the most influential collection of church law, included a section justifying wars {{circa|1140}}—but only against heretics.{{sfn|Jaspert|2006|p=65}}{{sfn|Tyerman|2011|p=24}} Within a few decades, jurists such as Huguccio began applying Gratian's arguments to conflicts against Muslims. They cited righteous intent, the recovery of unlawfully held Christian lands and the retaliation for violence against Christians as justifications.{{sfn|Tyerman|2011|p=24}} Crusades against pagans were initially framed as acts of self-defence, but the pagans' conversion became the primary aim of the Northern Crusades in the early {{nowrap|13th century}}.{{sfn|Jotischky|2017|p=218}} Crusades against the Christian adversaries of the papacy were justified as necessary to enable the Church to defend the Holy Land effectively.{{sfn|Tyerman|2019|p=359}}

{{Main|Crusade indulgence}}

File:Heidelberg cpg 144 Elsässische Legenda Aurea 338r St. Patricks Fegefeuer.jpg, depicting the sinners' (temporal) punishment in the Purgatory]]

Soon after Clermont, the chronicler Guibert of Nogent observed that "God has instituted in our times holy wars, so that the order of knights and the crowd running in its wake ... might find a new way of gaining salvation".{{sfn|Riley-Smith|2002|p=78}} Yet the nature of the spiritual rewards for the First Crusaders remains uncertain. Some sources mention the cancellation of temporal penance; others refer to the complete remission of sins.{{refn|group=note|Bishop Lambert of Arras who was present at Clermont wrote that those who departed for the Holy Land "could substitute this journey for all penance"; another participant, the chronicler Robert of Rheims said that Urban had granted the remission of sins to the crusaders; according to a third eyewitness, Baldric of Dol, the Pope ordered the bishops to grant absolution only to those who had confessed their sins.{{sfn|Bysted|2014|pp=46–47, 49}}}}{{sfn|Jaspert|2006|p=31}}{{sfn|Jotischky|2017|p=54}} Pope Urban himself spoke of {{Transliteration|la|remissio peccatorum}} ('remission of sins') in one letter, and in an other, he promised that those who journeyed to the Holy Land "only for the salvation of their souls" would be absolved of all penance, provided they confessed their sins.{{sfn|Bysted|2014|pp=67–68}} His successors often used the formula {{Transliteration|la|remissio peccatorum}}, but other phrases—such as {{Transliteration|la|peccatorum absolutionem}} ('absolution of sins') and {{Transliteration|la|venia peccatorum}} ('forgiveness of sins')—also appeared.{{sfn|Bysted|2014|p=181}}

Theological discussion of indulgences began {{circa|1130}}. Peter Abelard criticized the practice sharply, but later theologians mainly treated it as a common practise.{{sfn|Bysted|2014|pp=85–112}} The Fourth Lateran Council standardized crusade indulgence in 1215, declaring that "sins repented by heart and confessed with mouth" would be remitted. Still, the theological foundation remained ambiguous until {{circa|1230}}, when the doctrine of "Treasury of Merit" emerged. It held that Christ's and the martyrs' sacrifices accumulated spiritual merit, stored by the Church, and available for granting indulgences.{{sfn|Bysted|2014|p=132–135}}{{sfn|Jotischky|2017|p=192}} Debate over the scope of crusade indulgences persisted. The theologian Bonaventure argued that those who died before fulfilling their crusading vow could not receive a plenary indulgence. In contrast, the great scholastic Thomas Aquinas maintained that remorseful crusaders who confessed their sins would attain salvation even if they died before departing.{{sfn|Bysted|2014|pp=142–143}}

{{See also|List of principal crusaders}}

An individual crusader's motives for joining a crusade can never be fully determined. While primary sources emphasise religious fervour, wordly ambitions must also be considered, since it was clear from the outset that defending the conquered territories would require permanent Western presence.{{refn|group=note|A version of Pope Urban's call for the First Crusade, written by the chronicler Robert the Monk, explicitly refers to the possibility of material gains.{{sfn|France|1999|p=205}}}} Both soldiers and support personnel often joined crusades in exchange for salary.{{sfn|Tyerman|2019|p=202}} For many crusaders, spirituality was compatible with purely material activities, such as looting.{{sfn|Jotischky|2017|p=39}}{{sfn|Phillips|2014|p=21}} Contemporary accounts suggest that some sought fame, while the historian Jonathan Phillips assumes that a strong desire for travel also played a role.{{sfn|Phillips|2014|pp=21–23}} The medievalist Andrew Jotischky suspects that some saw the crusades as a chance for unpunished violence.{{refn|group=note|The par excellence robber baron Thomas of Marle was praised as a valiant knight "with a loyal heart" in a contemporary {{Transliteration|fr|chanson de geste}} for his bravery during the First Crusade, but he had eagerly put Jews to sword at the beginning of the campaign.{{sfn|Jotischky|2017|pp=39–40}}}}{{sfn|Jotischky|2017|pp=39–40}}

File:Peraldus Knight.jpg. The allegory presents a knight prepared to fight the seven deadly sins.]]

A scion of a French noble family, Pope Urban addressed his speech at Clermont to France's military elite.{{sfn|Jotischky|2017|p=56}} While originally a diverse social group, the {{Transliteration|la|milites}} had by then become a distinct class; however, knighthood became fully equated with nobility only in the late {{nowrap|12th century}}.{{sfn|Tyerman|2019|p=53}} Aristocrats placed high importance on public displays of piety, and crusading offered a new outlet for what Madden calls their "simple and sincere love of God".{{sfn|Madden|2013|pp=12–13}}

The aristocrats' martial lifestyle involved frequent sin yet left few opportunity for penance. Moreover, traditional pilgrimages on foot stripped them of their status symbols—arms and war horses. Urban's message presented a way to uphold their values without jeopardizing salvation.{{refn|group=note|Crusade indulgence held particular appeal for aristocrats burdened by guilt. The French knight Odo Bevin, for example, joined the First Crusade instead of entering a monastery to atone for earlier conflicts with it. Similarly, the troubled conscience of the Italo-Norman aristocrat Tancred was reportedly eased upon hearing Urban's call.{{sfn|Riley-Smith|2002|pp=78–79}}}}{{sfn|Bull|2002|p=33}}{{sfn|Riley-Smith|2002|pp=78–79}} Crusade rhetoric often echoed the warrior class's moral code, invoking themes like vassalage and honour.{{sfn|Jaspert|2006|p=20}} Preachers portrayed Christ as a feudal lord, calling knights to fulfill their duty to fight for him.{{sfn|Madden|2013|p=9}} Crusaders saw themselves as {{Transliteration|la|milites Christi}} ('Christ's warriors') fighting for their lord's stolen patrimony.{{refn|group=note|Originally, the term {{Transliteration|la|miles Christi}} referred to priests wealding spiritual arms in God's service.{{sfn|Jaspert|2006|p=19}}}}{{sfn|France|1999|p=205}}

Crusading decisions were typically made within broader networks under the leadership of a powerful lord.{{sfn|Jotischky|2017|p=16}} Knights who fought in a successful campaign earned great prestige,{{refn|group=note|In 1106, the crusader Bohemond of Taranto visited France, married Constance, daughter of King Philip I, and was widely sought after as a godfather by the nobility.{{sfn|Riley-Smith|2002|p=72}}}} and the imitation of crusader kinsmen could turn crusading into a family tradition.{{refn|group=note|Three sons of William I, Count of Burgundy joined the First Crusade; one grandson and one granddaughter participated in a crusade during the 1120s; and seven of his descendants took part in the Second Crusade.{{sfn|Riley-Smith|2002|pp=81, 86}}}}{{sfn|Riley-Smith|2002|pp=281}} However, failed campaigns brought risk—disgrace and financial ruin were real possibilities.{{sfn|Riley-Smith|2002|p=72}}{{sfn|Tyerman|2019|pp=491 (note 37)}} Chivalric nostalgia drove at least two failed late medieval crusades: the Barbary Crusade against northern African corsairs in 1390, and the Crusade of Nicopolis against the Ottomans in 1396.{{sfn|Madden|2013|p=181}}

Although shedding blood was theoretically incompatible with their vocation, priests often joined the crusades.{{sfn|Nicholson|2004|p=xlii}} At Clermont, Bishop Adhemar of Le Puy was the first to declare his intent to journey to Jerusalem.{{sfn|Riley-Smith|2002|p=1}} The Fourth Lateran Council explicitly permitted clerics to join a crusade for up to three years without forfeiting the full income from their benefices.{{sfn|Brundage|1997|p=150}} Secular clerics typically served as chaplains or administrators,{{sfn|Jaspert|2006|p=62}}{{sfn|Tyerman|2019|p=226}} while senior churchmen often commanded troops and led military operations.{{refn|group=note|Among the earliest crusading prelates, Archbishop Daimbert of Pisa led a fleet of 120 ships to the Levant and, alongside Bohemond of Taranto, attacked the Byzantine port of Latakia in 1099.{{sfn|Lock|2006|pp=25, 234}}{{sfn|Tyerman|2007|p=161}} During the first Northern Crusade, seven bishops led the assault on the town of Demmin.{{sfn|Christiansen|1997|p=55}}}}{{sfn|Tyerman|2019|p=226}} Influential prelates played key roles in initiating Northern Crusades.{{refn|group=note|Archbishop Eskil of Lund threatened Valdemar I of Denmark with excommunication to compel an attack on the pagans on the island of Rügen, then joined the fight himself. His successor, Absalon, as the historian Eric Christiansen notes, spent "most of his life in the sadle or on the gangway of his ship", battling both heathens and Christian rivals.{{sfn|Christiansen|1997|pp=60–61}}}}{{sfn|Jaspert|2006|p=126}} Monastic vows, particularly {{Transliteration|la|stabilitas voci}} ('stability of place'), formally barred monks from joining a crusade, yet this was frequently ignored.{{sfn|Nicholson|2004|p=xlii}}{{sfn|Jaspert|2006|p=62}} Cistercian and Premonstratensian monks occasionally took up arms during the Northern Crusades.{{refn|group=note|The Cistercian monk Bern became a missionary bishop among the Abodrites and took part in the 1168 invasion of Rügen.{{sfn|Christiansen|1997|p=62}}}}{{sfn|Christiansen|1997|pp=59–60}}

Members of the urban elite played a key role in several crusades.{{sfn|Tyerman|2019|p=227}} Fleets from Genoa, Pisa and Venice aided in establishing and consolidating the Crusader states.{{refn|group=note|The Genoese patrician Guglielmo Embriaco joined the crusaders besieging Jerusalem in June 1099; the Venetian patrician Giovanni Michiel supported the crusaders to capture the city of Haifa in the late summer of 1100.{{sfn|Lock|2006|pp=384–386}}}} In return, they received commercial privileges, quarters in captured cities, and at times rural estates.{{refn|group=note|The {{Transliteration|la|Pactum Warmundi}} acknowledged the Venetians' claim to more than twenty villages in the region of Tyre in return for their naval assistance during the siege of the city in 1123–24. These villages were distributed among Venetian patricians as hereditary fiefs held directly from the Crown in the Lordship of Tyre.{{sfn|Jotischky|2017|pp=162–163}}{{sfn|Jacoby|2016|pp=182–183}}}}{{sfn|Lock|2006|pp=382–387}} The conquest of Prussia was supported by the wealthy Baltic city, Lübeck.{{sfn|Christiansen|1997|p=104}} In Iberia, cities and towns owed military service as defined in royal charters, though these duties were often commuted through a special tax called {{Transliteration|es|fonsadera}}.{{sfn|O'Callaghan|2003|p=129}}

During the Fourth Crusade, the Venetian doge Enrico Dandolo convinced fellow crusader leaders to seize the Catholic city of Zadar on the Dalmatian coast, and later advocated for the attack on Constantinople. Following the city's sack, the Venetians took control of several Aegean Islands, turning them into lordships ruled by Venetian patricians.{{refn|group=note|For instance, Marco I Sanudo seized Naxos and the nearby islands, establishing the Duchy of the Archipelago.{{sfn|Lock|1995|pp=147–148}}}}{{sfn|Jaspert|2006|pp=52–53}}{{sfn|Phillips|2014|pp=184–200}}

Marino Sanudo Torsello, a Venetian, emerged as a prominent crusade theorist.{{sfn|Madden|2013|pp=12–13}} He was the first to propose a naval league against Aegean pirates, involving Catholic powers and island lords from Venice and Genoa.{{sfn|Carr|2016|pp=68–69}} Pope John XXII approved the first such league in 1334.{{sfn|Carr|2016|p=99}}

File:Croisade des Pastoreaux Britisch Librairy.jpg (a miniature from the late-14th-century {{Transliteration|fr|Chroniques de France ou de St-Denis}})]]

The historian Christopher Tyerman observes that "crusading can be seen as much as a phenomenon of artisans as of knights, of carpentry as much as of castle". Commoners filled essential roles in crusader armies as foot soldiers, sailors, archers, engineers, and squires, and household servants. A typical common crusader was a young man with modest property who joined for pay. Thus, Tyerman notes, "the image of crowds spontaneously leaving fields or workshops to follow the cross is largely mythical".{{sfn|Tyerman|2019|pp=227–228}}

Following Clermont, Pope Urban barred clergy from accepting crusader vows from those unable to fight and annulled existing ones.{{sfn|Madden|2013|p=10}} Still, the People's Crusade consisted almost entirely of unarmed commoners,{{sfn|Kostick|2008|p=290}} inspired by unauthorised preachers like Peter the Hermit whom many viewed as a living saint.{{sfn|Asbridge|2012|p=40}} In the First Crusade's princely armies, non-combatants nearly matched the number of fighters, prompting the historian Conor Kostick to call it "a slice of European society on the march".{{sfn|Kostick|2008|pp=289–290}} Chroniclers like Raymond of Aguilers referred to the common crusaders as {{Transliteration|la|pauperes}} ('the poor/defenceless'). Raymond considered their presence vital for divine favour. Another frequent label, {{Transliteration|la|rustici}}, reflected their rural origins.{{sfn|Kostick|2008|pp=30–34}} Captured commoners were often tormented or killed, unlike aristocrats, who were usually held for ransom.{{sfn|Friedman|2001|p=124}}

Grassroots crusading zeal gave rise to later mass movements known as popular crusades.{{sfn|Tyerman|2019|p=259}}{{sfn|Dickson|2006|p=975}} These included the 1212 Children's Crusade (sparked by two charismatic boys),{{refn|group=note|Contemporary sources referred to the participants as {{Transliteration|la|pueri}} ('children'), which gave the movement its name; however, as Tyerman explains, the term more accurately reflected their marginal status in society than their age.{{sfn|Tyerman|2019|p=260}}}} the 1251 Shepherds' Crusade (inspired by a supposed letter from the Virgin Mary), the 1309 Crusade of the Poor (linked loosely to an official crusade in the Aegean), and the 1320 Shepherds' Crusade. None reached the Holy Land, and both Shepherds' Crusades were forcibly disbanded because of violence.{{sfn|Lock|1995|pp=166, 187, 190}}{{sfn|Tyerman|2019|pp=258–260}} In 1456, a peasant crusader army tipped the balance in the defenders' favour during the Ottoman Siege of Belgrade. This success set a precedent for mobilizing peasants in anti-Ottoman crusades, but in 1514 the assembled serfs turned on their lords in Hungary.{{sfn|Tyerman|2019|pp=411–412}}

File:Double page from the Qur'an manuscript containing the opening to juz' 13 (DMA K.1.2014.574.1).jpg of the Quran, placed in the madrasa of Nur al-Din in Damascus]]

Muslim legal experts divided the world into two spheres, the Muslim world, or {{Transliteration|ar|Dar al-Islam}} ('Abode of Islam'), and the non-Muslim world, or {{Transliteration|ar|Dar al-harb}} ('Abode of War'). Border regions like Syria and Iberia were battlegrounds of {{Transliteration|ar|jihad}}, attracting {{Transliteration|ar|mujahideen}} and {{Transliteration|ar|ghazis}}—Muslim volunteers—from other regions.{{sfn|Hillenbrand|2018|pp=97–101}}{{sfn|Cobb|2016|pp=9, 33}} Accounts on Christians' experiences in the Holy Land on the eve of the First Crusade vary.{{refn|group=note|The contemporary Muslim scholar Abu Bakr ibn al-Arabi did not mention anti-Christian violence, but the 12th-century historian al-Azimi reported that the "people of the Syrian ports" had obstructed Christian pilgrims from reaching Jerusalem.{{sfn|Asbridge|2012|p=28}}}}{{sfn|Asbridge|2012|p=28}} As Jotischky notes, sporadic attacks on pilgrims likely shaped the perception that Christians "were under threat".{{sfn|Jotischky|2017|p=40}} However, emphasises Asbridge, interreligious conflicts mirrored the "endemic political, military and social struggles of the age".{{sfn|Asbridge|2012|pp=28–29}}

Western Christians often considered the Muslims as idol-worshippers or heretics.{{sfn|Jaspert|2006|p=9}}{{sfn|Bull|2002|p=20}} Until {{circa|1110}}, mass killings of Muslim inhabitants in conquered towns were not uncommon.{{refn|group=note|One of the earliest examples of mass violence was the massacre of civilians in Ma'arra, followed by the crusaders' wholesale slaughter of Muslims in Jerusalem after its capture.{{sfn|Tyerman|2007|pp=157–158}}}}{{sfn|Mallett|2020|p=26}}{{sfn|Jotischky|2017|p=137}} Crusaders generally showed little interest in converting the Levantine Muslims, instead imposing a poll tax akin to the {{Transliteration|ar|jizya}}.{{sfn|Jotischky|2017|pp=137–139}} In the Crusader states, most Muslims were Arabic-speaking farmers. They lived in communities headed by their own chiefs who administered justice based on Islamic law.{{sfn|Jaspert|2006|p=96}} In Iberia, the {{Transliteration|es|mudejares}}—Muslims under Christian rule—were also treated as second-class citizens.{{sfn|Jaspert|2006|pp=124–125}}{{sfn|Cobb|2016|p=170}}{{sfn|Lock|2006|p=135}} Church law included discriminatory measures, though enforcement is unclear.{{refn|group=note|In 1120, the Council of Nablus issued decrees mandating the castration of Muslim men who had relations with Christian woman, and the mutilation, specifically the cutting of the nose, of Christian women who had slept with Muslim men.{{sfn|Jotischky|2017|p=140}}}}{{sfn|Jotischky|2017|p=140}}

Initially, few Muslims grasped the crusaders' religious zeal. The Damascene scholar Ali ibn Tahir al-Sulami was the first to frame the crusades within the wider expansion of the "Franks", or westerners, in the Mediterranean.{{sfn|Jaspert|2006|p=75}}{{sfn|Madden|2013|p=43}} He interpreted their success as a sign of divine retribution for the waning spirit of {{Transliteration|ar|jihad}}.{{sfn|Cobb|2016|p=39}} Zengi was among the first Muslim leaders of the crusading era to be honored with {{Transliteration|ar|jihadist}} titles, such as "leader of those who fight the Holy War". Afterward, Muslim rulers often emphasised religious motives for fighting the Franks.{{sfn|Hillenbrand|2018|pp=111–249}} In Iberia, the Almoravids and the Almohads were the most ardent champions of the {{Transliteration|ar|jihad}}.{{sfn|Jaspert|2006|pp=118–121}} Still, despite heavy religious rhetoric on both sides, alliances between Christian and Muslim rulers were fairly common.{{refn|group=note|Viewing the {{Transliteration|ar|jihadist}} efforts of the Seljuq sultan Muhammad as a strategy to extend his dominion, the Muslim rulers of Aleppo and Damascus allied with the Franks of Antioch and Jerusalem to repel a Seljuk invasion in 1115.{{sfn|Jotischky|2017|p=115}}{{sfn|Lock|2006|p=32}} In 1196, Alfonso IX of León invaded Castile in collaboration with the Almohads, prompting {{nowrap|Pope Celestine III}} to grant crusade indulgence to those who would take up arms against him.{{sfn|Tyerman|2007|p=666}}}}{{sfn|Jotischky|2017|pp=115, 119, 122}}{{sfn|Cobb|2016|p=64}}

File:Elias IMG 0510.JPG near Bethlehem. Its restoration was financed by the Byzantine emperor Manuel I Komnenus during the crusading period.{{sfn|Jotischky|2017|p=154}}]]

The liberaton of eastern Christians was proclaimed a central goal of the First Crusade, yet early encounters between Crusaders and native Christians proved disappointing for both sides.{{sfn|Jotischky|2017|pp=133–134}} The influx of the First Crusaders into Byzantine lands alarmed Emperor Alexios, who had anticipated disciplined mercenaries or manageable allies. Concerned about the crusade leaders' territorial ambitions, he secured pledges that all reconquered Byzantine lands would be returned.{{sfn|Lilie|1993|pp=2–12}} Despite this, Bohemond kept Antioch—a former Byzantine provincial capital—for himself.{{sfn|Lilie|1993|pp=40–41}} Days after conquering Antioch, Crusader leaders labeled local Christians as "heretics" in a letter to Pope Urban.{{sfn|MacEvitt|2008|p=1}} In 1099, the Catholic clergy temporalily barred native clerics from the Holy Sepulchre.{{refn|group=note|In the Holy Sepulchre, Christ's resurrection had traditionally been commemorated by the lighting of candles from a flame believed by the faithful to descend miraculously from above. Native clergy were readmitted at Eastern 1101, as Catholic priests had failed to sustain the ritual celebration.{{sfn|MacEvitt|2008|p=115}}}}{{sfn|MacEvitt|2008|pp=115–119}} Eastern Christians were subjected to a poll tax in the Crusader states, marking their subordinate status, but their right to self-governance was acknowledged,{{sfn|Jotischky|2017|p=138}} and some retained substantial landholdings.{{sfn|MacEvitt|2008|pp=144–150}}

Known as Melkites, Orthodox Christians comprised the majority of the native Christian population in Palestine and were also prominent in northern Syria.{{sfn|MacEvitt|2008|p=8}} Catholic theologians considered them schismatics, not heretics. In Antioch, Crusaders reinstated John the Oxite as Orthodox patriarch, though later exiled him during a conflict with the Byzantines in 1100. Most Orthodox bishops had fled Palestine before the First Crusade, but scattered references to Orthodox prelates suggest an Orthodox hierarchy under Frankish rule.{{refn|group=note|A notable example is Meletos, the Orthodox bishop of Gaza, who retained his position after the city fell to the Franks in 1149. The historian Christopher MacEvitt attributes this to the Templars, Gaza's new rulers, noting that appointing a Catholic bishop might have provoked disputes over tithes and properties.{{sfn|MacEvitt|2008|pp=112–113}}}}{{sfn|MacEvitt|2008|pp=100, 110–111}} Orthodox monasticism revived, supported largely by Byzantium, with many monasteries rebuilt and reoccupied.{{sfn|Jotischky|2017|pp=154–155}}

Several eastern Christian communities, unlike the Catholics and Orthodox, rejected the Christological rulings of the 451 Council of Chalcedon. Among them, the Armenians—concentrated in northern Syria and Cilicia{{sfn|MacEvitt|2008|pp=7–9}}—were the most respected by the Franks for they had their own autonomous lordships.{{sfn|Jotischky|2017|p=136}} Many welcomed the Crusaders as liberators and collaborated with them. Intermarriage between Armenian and Frankish elites was not unusual and eventually legitimised the Frankish Lusignans' claim to rule Cilician Armenia.{{sfn|Lock|2006|pp=378–381}} Political motives also led to a tenuous church union between the Cilician Armenian Church and the Holy See in 1198.{{sfn|Ghazarian|2005|pp=123–124, 189–190}} Anti-Chalcedonian Syriac (or Jacobite) communities, primarily in northern Syria and Mesopotamia,{{sfn|MacEvitt|2008|pp=8–9}} consisted mostly of unarmed, Arabic-speaking villagers. The early-13th-century Catholic bishop Jacques de Vitry described them as "useless as women in battle".{{sfn|Jotischky|2017|p=136}} Another distinct group, the Maronites of Mount Lebanon remained unmentioned in Catholic writings until 1181, when they entered into communion with Rome, forming the first Eastern Rite Catholic Church.{{sfn|MacEvitt|2008|p=9}}

Relations between Byzantines and the Crusader states fluctuated between hostility and cooperation.{{sfn|Lilie|1993|pp=72–73, 168–169, 177, 246–253}} Following the Fourth Crusade, Byzantine successor states like Epiros and Nicaea led local resistance effort, although rivalries sometimes led to temporary Greek–Frankish alliances.{{refn|group=note|To secure an alliance against Nicaea, the Epirote ruler Michael II Komnenos Doukas married his daughter Anna to William of Villehardouin, the Frankish prince of Achaea; however, their joint forces were defeated by the Nicaeans at Pelagonia in 1259.{{sfn|Lock|1995|p=83}}}}{{sfn|Lock|1995|pp=80–83}} In Frankish Greece, many Greek {{Transliteration|el|árchontes}} (or aristocrats) preserved their estates and fought alongside Frankish knights, though Greek peasants experienced worsening conditions compared to the Byzantine era.{{sfn|Lock|1995|pp=284–288}} Orthodox bishops who rejected papal supremacy were replaced by Catholic counterparts, but the papacy protected Greek monastic institutions.{{sfn|Lock|1995|pp=205–209, 226–228}} The Frankish conquest of Byzantine territories reinforced local Orthodox identity, and widespread resistance ensured the failure of attempts to reunite the Catholic and Orthodox churches.{{refn|group=note|The final Byzantine emperors, John VIII and Constantine XI Palaiologos, endorsed the church union established at the Council of Florence in 1439, hoping it would secure Western aid against the Ottomans. However, they were unable to overcome the entrenched opposition of the Byzantine clergy and laity.{{sfn|Tyerman|2019|p=401}}}}{{sfn|Tyerman|2019|pp=399–401}}

In northeastern Europe, Catholic and Orthodox churches co-existed in major trading centers, and the schism did not prevent interfaith dynastic marriage between royalty. Catholic missionary activity intensified only after the Fourth Crusade. Internal rivalries among Rus' princes and within the Novgorod Republic occasionally lead to temporary alliances with Crusaders, but no lasting conquests of Rus' lands were achieved.{{sfn|Christiansen|1997|pp=132–137}}

File:Papal bull regarding Lithuanian ruler Mindaugas 1251.jpg's papal bull about the baptism and coronation of the Lithuanian ruler Mindaugas]]

Trade in raw materials and slaves had established lasting contact between Christian and pagan communities in the Baltic region well before the crusades, though rivalries over trade routes often escalated into open conflict.{{sfn|Christiansen|1997|pp=43–49}} Intensified German colonisation and the unequal access to natural resources led to more frequent clashes between the Wends and their Christian neighbours from {{circa|1100}}.{{sfn|Bartlett|1994|p=136}}{{sfn|Christiansen|1997|p=136}} When promoting the Second Crusade in 1146, the Cistercian Bernard of Clairvaux found the Saxon lords unwilling to abandon their campaigns against the Wends for a journey to the Holy Land. Viewing pagan conversion as essential for the Devil's ultimate defeat, he adopted their perspective, and convinced {{nowrap|Pope Eugenius III}} to authorise an anti-Wendish crusade.{{sfn|Asbridge|2012|p=213}}{{sfn|Christiansen|1997|p=5}} The Wends' structured society, with principalities, towns, and priestly hierarchy, eased their integration into the Christian world.{{refn|group=note|The Wendish ruler Nyklot was the primary target of the Wendish Crusade in 1147. His son, Pribislav became the first Christian prince of Mecklenburg in 1160. Pribislav's son, Henry Borwin I joined a crusade in the eastern Baltic in 1218, while his grandson Henry I was captured by Muslim forces during a pilgrimage to the Holy Land.{{sfn|Christiansen|1997|p=72}}{{sfn|Bartlett|1994|pp=53–56, 61, 69, 180, 26, 276}}}}{{sfn|Tyerman|2019|p=308}}

To the east, Baltic peoples had resisted Christian proselytism for centuries. Most—such as the Old Prussians, Latvians, Curonians—lived in rural communities led by local strongmen who amassed wealth through trade and raiding.{{sfn|Christiansen|1997|pp=36–40}} Crusaders used coercion and bribery, and promises of protection from mutual enemies to secure conversions.{{sfn|Christiansen|1997|pp=95–101}} Though papal legates made repeated efforts to shield converted Balts from exploitation, they achieved little success.{{refn|group=note|Under the 1249 Treaty of Christburg, concluded between the papal legate Jacques Pantaléon and the Teutonic Knights, Christian native lords were formally granted the same rights as their German and Polish counterparts. However, following the Prussian uprisings of 1259 and 1263, the Knights limited these privileges to only the most loyal members of the native aristocracy.{{sfn|Christiansen|1997|pp=130–131}}{{sfn|Tyerman|2019|p=326}}}}{{sfn|Christiansen|1997|pp=130–131}}

The Lithuanians, the fourth major Baltic group, were mostly peasants owing taxes and services to native lords. Surrounded by external threat, Lithuania unified under Grand Prince Mindaugas in the {{nowrap|13th century}}. He was baptised and received a royal crown from Pope Innocent IV in 1253, but his successors reverted to paganism and extended control over Orthodox Rus' principalities like Polotsk and Kyiv.{{sfn|Christiansen|1997|pp=xiv, 140–176}} In 1386, Grand Prince Jogaila married Queen Jadwiga of Poland and became King {{nowrap|Władysław II}}. The resulting mass conversion of Lithuanians to Catholicism undermined the Teutonic Knights' justification for continued anti-Lithuanian crusades. In 1410, Polish and Lithuanian forces decisively broke the Knights' power at Tannenberg. The {{Transliteration|de|Preussenreise}} lost popularity, and the last non-German crusaders entered the Baltic in 1413.{{sfn|Nicholson|2004|p=51}}{{sfn|Christiansen|1997|pp=145, 227–230}}

In the easternmost Baltic, Finnic peoples lived in small rural communities. Alongside agriculture and slave-raiding, they hunted for valuable furs.{{sfn|Christiansen|1997|pp=41–43}} Legend holds that the Swedish king Eric IX launched the first crusade into Finland in the late 1150s, but the earliest confirmed crusade was proclaimed by Pope Gregory IX in 1237.{{sfn|Christiansen|1997|pp=113–117}}{{sfn|Lock|2006|p=223}} Danish crusaders conquered Estonia in 1219, though by mid-century, German knights and burghers had come to dominate the region's political life.{{sfn|Christiansen|1997|pp=199–200}}

File:Le massacre des Albigeois.jpg at the beginning of the Albigensian Crusades.]]

The Gregorian Reform failed to satisfy those seeking a purer, simpler form of Christianity. The Waldensians, the first significant dissident group, praised poverty and preached in the vernacular.{{sfn|Backman|2022|pp=379–381}} Increasing trade facilitated the westward spread of dualist ideologies, which distinguished between a pure, incorruptible God and an evil creator of the material world, rejecting the mainstream Christian doctrine of the Incarnation. In Western Europe, these groups became known as Cathars or Albigensians.{{sfn|Tyerman|2007|pp=568–575}}

Catholic churchmen viewed heresy as a fundamental threat to Christianity and believers' salvation.{{sfn|Madden|2013|p=117}} As early as 1179, the Third Lateran Council endorsed the use of force against heretics and promised indulgences to those who fought them.{{sfn|Tyerman|2019|p=344}} However, Cathars were well integrated into Occitan society in southern France, and local elites were often unwilling to act against heretical family and friends.{{sfn|Tyerman|2007|p=575}}

In 1207, Pope {{nowrap|Innocent III}} urged Raymond VI, Count of Toulouse, to eradicate heresy from his territories. Raymond's reluctance or inability to respond led the papal legate Peter of Castelnau to excommunicated him. The legate was soon murdered, prompting Innocent to declare a crusade.{{sfn|Jotischky|2017|p=186}}{{sfn|Tyerman|2007|pp=582–584}} Crusaders, mostly from northern France, invaded Occitania, committing brutal acts against both Cathars and Catholics.{{refn|group=note|The crusade theorist Caesarius of Heisterbach claimed that the Cistercian abbot Arnaud Amalric had urged the Crusaders to kill everybody, stating that "The Lord knows who are his own" during the Massacre at Béziers. In the same town, prelates called the slaughter of {{circa}} 20,000 people as a miracle.{{sfn|Tyerman|2007|pp=480, 591, 962 (note 59)}}}}{{sfn|Jotischky|2017|pp=186–187}} While the campaigns deepened French control over the region, it failed to eliminate heresy. That goal was eventually achieved by mendicant friars and inquisitors with support from secular authorities.{{sfn|Jaspert|2006|p=137}}

In northern Germany, a crusade targeted peasants accused of heresy and witchcraft for refusing to pay the tithe (church tax).{{sfn|Jaspert|2006|p=142}} Hungarian rulers, aiming to expand into Bosnia, launched two failed crusades against the region, allegedly home to a Cathar antipope.{{sfn|Lock|2006|p=172}} In contrast, the {{Transliteration|it|Apostolici}}, a radical dissident group in northern Italy, were decisively eradicated by Crusaders.{{sfn|Jaspert|2006|p=138}}

File:BitvaULehnice.jpg after the Battle of Legnica (from a mid-15th-century Legend of his mother St Hedwig)]]

Western Europeans first became aware of the Mongol conquests during the Fifth Crusade.{{sfn|Tyerman|2007|p=641}} The Mongol Empire had emerged in 1206 when the talented military commander Temüjin was proclaimed supreme ruler as Genghis Khan.{{sfn|Mayer|2009|pp=267–268}} Some Mongol tribes followed the Eastern Syrian (or Nestorian) Church.{{sfn|Jotischky|2017|p=257}} Although Nestorians had separated from mainstream Christianity in 431,{{sfn|MacEvitt|2008|p=10}} fragmented reports about of Mongol advance revived legends of a powerful eastern Christian ruler, Prester John, a potential ally against Islam.{{sfn|Madden|2013|p=165}}

The Mongols, however, were convinced they were divinely destined to conquer the world.{{sfn|Mayer|2009|p=268}} Their devastating invasion of eastern and central Europe in 1239–40 deeply shocked Western Christendom. Pope {{nowrap|Gregory IX}} called for a crusade, but the Mongols withdrew only because of the death of Genghis's successor, Ögedei Khan in late 1241.{{sfn|Lock|2006|p=176}}{{sfn|Mayer|2009|p=269}} In 1258, Mongol forces captured Baghdad and destroyed the Abbasid Caliphate. Seeking protection, the Cilician Armenian king Hethum I and his son-in-law, Bohemond VI of Antioch submitted to Hulegu, the Mongol {{Transliteration|mn|il khan}} (ruler of the Middle East). Mongol expansion in the region was brought to halt when the Mamluks defeated Hulegu's forces at Ain Jalut in 1260.{{refn|group=note|Paradoxically, the rise of the Mamluks can be traced to the Mongol destruction of the nomadic Cumans in Eastern Europe, as many Cumans were captured and sold into slavery in Egypt, where they became part of the Ayyubid sultan's {{Transliteration|ar|mamluk}} ('slave soldier') guard.{{sfn|Cobb|2016|p=220}}}}{{sfn|Jotischky|2017|pp=257–258}}

{{Main|History of the Jews and the Crusades}}

Roman legislation under the first Christian emperor Constantine the Great and Augustine's theological works laid the foundation of the Western Christians' general attitude to Judaism. Constantine recognised Judaism as a legal denomination but restricted the Jews' rights; Augustine admitted that the Jews were protected by God, but also stated that God had punished them with their dispersion for having failed to recognise Jesus as the godly appointed Messiah.{{sfn|Chazan|2006|pp=27–38}} The Jews' expansion in Western Europe began in parallel with the economic boom that preceded the crusades.{{sfn|Lock|2006|p=397}} Coming from the developed Islamic economies, Jewish merchants applied advanced commercial know-how. As they could ignore the anti-usury decrees of canon law, they quickly took control of moneylending, which reinforced antisemitism.{{sfn|Chazan|2006|pp=217–219}}

The local rulers mainly appreciated the Jews' economic role and offered them protection, but this protection was fragile in a hostile environment. As early as 1010, distorted news of the destruction of the Holy Sepulchre triggered antisemitic attacks in the towns of Limoges, Rouen and Mainz.{{sfn|Lock|2006|p=397}} The western Jewish communities first faced coordinated pogroms in the Rhineland at the beginning of the First Crusade. The crusaders reportedly wanted to take vengeance on the Jews for Christ's crucifixion, but their desire to seize Jewish property is well-documented.{{sfn|Tyerman|2019|pp=80–81}}{{sfn|Lock|2006|pp=397–398}} In the east, the Jews of Jerusalem were slaughtered by the first crusaders.{{sfn|Lock|2006|p=399}} The Jewry of other towns (such as Tyre and Ascalon) survived, and Jewish pilgrimage to the Holy Land intensified from the {{nowrap|12th century}}, leading to the settlement of hundreds of western Jews in Palestine.{{sfn|Jaspert|2006|pp=98–99}}

Preaching for crusades led to antisemitic attacks throughout the {{nowrap|12th century}}. In 1146, the renegade monk Radulph stirred up pogroms in Rhineland, but Bernard of Clairvaux ordered his imprisonment. In 1189 and 1190, the mob attacked Jews in English towns.{{sfn|Lock|2006|pp=400–401}}{{sfn|Tyerman|2019|p=82}} Antisemitism escalated to a new level with the spread of unfounded gossip about the ritual murder of Christian children by Jews from {{circa|1150}}.{{sfn|Tyerman|2019|p=82}}

{{Main|Women in the Crusades}}

File:Ida syni.jpg's farewell to her sons Godfrey of Bouillon and Baldwin of Boulogne departing for the First Crusade (a miniature from a 13th-century manuscript of the {{Transliteration|fr|Roman d'Alexandre}})]]

Women were closely associated with the movement from its beginning.{{sfn|Tyerman|2019|p=10}} Although popes discouraged female participation, female servants always accompanied crusading armies.{{sfn|Madden|2013|p=132}} Among them, washerwomen received special papal authorisation early on.{{sfn|Caspi-Reisfeld|2001|p=96}} While women needed the permisson of a father or husband to join a crusade, from 1209 men could decide without their wives' consent. High-ranking women occasionally led troops or conducted key diplomatic negotiations.{{refn|group=note|The widowed Austrian margravine Ida commanded her own army, and disappeared in the Battle of Heraclea in 1101. In Iberia, Ermengarde of Narbonne led a contingent during the siege of Tortosa in 1148. During the Seventh Crusade, Margaret of Provence led the negotiations about the ransom of her husband Louis IX of France with the Egyptian sultana Shajar al-Durr.{{sfn|Hodgson|2017|pp=49, 118, 211–212}}{{sfn|Tyerman|2019|pp=10–12}}}}{{sfn|Tyerman|2019|pp=10–12}} In the Baltic, female settlers actively participated in the defence of towns and villages.{{sfn|Hodgson|2017|p=49}} Sex workers also followed the armies though they were frequently expelled as part of purification efforts.{{sfn|Madden|2013|p=132}}

Gender-based bias is well documented among both crusaders and their opponents.{{sfn|Lock|2006|p=343}} Christian chroniclers primarily highlighted women's supportive roles—delivering water or stone missiles—but rarely mentioned female fighters.{{sfn|Caspi-Reisfeld|2001|pp=97–100}} By contrast, Muslim and Byzantine writers often described armed female crusaders, framing them as symbols of barbarism.{{sfn|Lock|2006|pp=343–344}} Muslim sources also condemned the relative freedom women in Frankish societies, viewing it as a gateway to debauchery.{{sfn|Madden|2013|pp=45–46}} Crusaders were expected to abstain from sex, often leading to women, including wives, being banished before major battles.{{sfn|Hodgson|2017|p=138}} Women left behind by crusading husbands or fathers were vulnerable to exploitation by kinsmen and neighbours.{{refn|group=note|The wife of the English crusader William Trussel was murdered and her body was profaned shortly after he had left for the Third Crusade. The only daughter of an other English crusader Ralph Hodeng married to one of his tenants during his absence.{{sfn|Riley-Smith|2002|p=74}}}} Some Crusaders made formal arrangements with kin or religious institutions to protect their wives and daughters; others entrusted their wives or mothers with managing their estates.{{refn|group=note|In France, female regency was quite common: both {{nowrap|Philip II}} and {{nowrap|Louis IX}} appointed their mothers—Adela of Champagne and Blanche of Castile, respectively—to rule during their absence. On the other hand, Louis charged two men Simon of Nesle and Matthew of Vendôme to govern his kingdom during his second crusade instead of his wife, Margaret of Provence.{{sfn|Hodgson|2017|pp=176–177}}}}{{sfn|Riley-Smith|2002|pp=73–75}}

Raids by both Christian and Muslim forces often targeted women, and after battles or sieges, victors frequently captured enemy women (and children).{{sfn|Friedman|2001|p=121}} The First Crusade was an exemption: Christian and Jewish sources report that entire populations of captured towns were massacred.{{sfn|Friedman|2001|pp=127–128}} In the Baltic, the Livonian Rhymed Chronicle praised the slaughter of pagan women and children as divinely-approved.{{sfn|Christiansen|1997|pp=95–96}} Captured women were frequently raped.{{sfn|Hodgson|2017|p=96}}{{sfn|Friedman|2001|p=126}} Noblewomen were held for ransom, though their value was usually lower than that of male counterparts. Those not ransomed were enslaved or married off.{{sfn|Friedman|2001|pp=124–133}}

Because of the high mortality of male warriors, women often inherited fiefs in the Crusader states, though they were expected to marry.{{sfn|Hodgson|2017|p=73}} Women could also inherit thrones: between 1186 and 1228, four queens ruled Jerusalem.{{refn|group=note|Sibylla ({{reign|1186|1190}}), her sister Isabella I ({{reign|1192|1205}}), Isabella's daughter Maria ({{reign|1205|1212}}), and Maria's daughter Isabella II ({{reign|1212|1228}}).{{sfn|Tyerman|2019|p=476}}{{sfn|Lock|2006|pp=484–485}}}}{{sfn|Hodgson|2017|p=77}} In Frankish Greece, the wives of Achaean barons captured in the Battle of Pelagonia formed the "Parliament of Dames" in 1261 to negotiate peace terms with the Byzantine Empire on their husband's behalf.{{sfn|Lock|1995|pp=303, 305}}

Tyerman notes that the "crusade paraded across society in recruitment, funding and social rituals of support". The movement was accompanied by various elements such as public processions, priestly blessings, acts of charity, and objects of visual art.{{sfn|Tyerman|2019|p=8}} Since the movement’s first century coincided with the so-called "Twelfth-Century Renaissance", a period marked by the rise of vernacular literature, it also inspired literary works.{{sfn|Routledge|2002|p=91}}

Most crusades were proclaimed by the pope, as only the Holy See could grant crusade indulgences. Calls for crusades typically appeared in papal bulls, outlining the causes, urging participation, and detailing the spiritual and secular benefits offered to participants.{{refn|group=note|The 1145 papal bull {{Transliteration|la|Quantum praedecessores}} ('As much as our predecessors') provided the template for subsequent encyclicals.{{sfn|Housley|2002|p=42}}}}{{sfn|Housley|2002|p=42}}{{sfn|Nicholson|2004|pp=xlvi–xlvii}} Crusade encyclicals were recited in all Catholic churches from the time of Pope Alexander III.{{sfn|Housley|2002|p=43}} Pope {{nowrap|Gregory IX}} authorised the Dominicans to preach Baltic crusades without further approval,{{sfn|Christiansen|1997|p=83}} a privilege later extended to the Franciscans and the Teutonic priests.{{sfn|Tyerman|2007|p=705}}

Crusades were promoted by clerics. Prelates holding legatine powers typically addressed aristocratic audiences during significant secular or church assemblies. Preaching in towns and villages was initially disorganised. Pope {{nowrap|Innocent III}} set up special commitees to cooperate local propaganda campaigns, but later popes preferred less formal methods. From the early {{nowrap|13th century}}, mendicant friars, trained for missionary tasks, took charge of local crusade preaching. By the end of the century, priests commonly utilised handbooks written by prominent crusade propagandist, like the Dominican friar Humbert of Romans.{{sfn|Housley|2002|pp=43–45}}

Individuals who choose to join a crusade made a public and solemn vow. Either at the same event or during a separate ceremony, a cloth or silk cross was sewn onto their mantle or robe. While red was the customary colour, other shades were occasionally used. By "taking the cross", crusaders demonstrated their commitment to follow Christ's call: "If any man will come after me, let him deny himself and take up his cross and follow me".{{sfn|Riley-Smith|2002|p=69}}{{sfn|Tyerman|2019|pp=4–5}} The symbol aligned with the 11th-century {{Transliteration|la|imitatio Christi}} ('imitation of Christ') movement, promoting an active apostolic life.{{sfn|Jaspert|2006|p=29}} Some crusaders also received traditional pilgrim emblems—a pouch and staff.{{sfn|Riley-Smith|2002|pp=691}}

Crusaders were required to wear the cross until their return, and those who removed it prematurely faced church censure for breaking their vow.{{refn|group=note|The excommunication of Emperor {{nowrap|Frederick II}} serves as a telling example. In 1227, he embarked on a crusade, but an outbreak forced him to return. Nevertheless, Pope Gregory IX excommunicated him for failing to fulfill his vow. Jotischky argues that Frederick’s efforts to consolidate his authority over the Church in Sicily may have been the true cause of his excommunication.{{sfn|Jotischky|2017|pp=237–238}}}}{{sfn|Riley-Smith|2002|p=71}} Suspension, commutation, or cancellation of the vow was permitted only in exceptional cases, including physical or mental weakness, or poverty.{{sfn|Lloyd|2002|p=48}} Wearing the cross became the crusaders' defining emblem, and by the late {{nowrap|12th century}}, they were commonly known in Latin as {{Transliteration|la|crucesignati}} ('signed with the cross').{{sfn|Tyerman|2019|p=5}}

The secular privileges offered to the first crusaders are poorly documented. According to a collection of canon law, crusaders and their goods were "under the Truce of God"; likewise, Guibert of Nogent notes that Pope Urban extended papal protection to the crusaders, their family, and property. Years later, his successor Pope Paschal II instructed French prelates to ensure returning crusaders recovered their property as Urban had "ordained in a synodal declaration".{{sfn|Brundage|1997|pp=141–143}} In 1107, the canonist Ivo of Chartres still referred to this legal protection as "new".{{refn|group=note|{{nowrap|Pope Paschal II}} had instructed Ivo to excommunicate the French nobleman Rotrou III, Count of Perche for constructing a fort on the land belonging to the crusader Hugh II of Le Puiset. However, Ivo hesitated, stating he did not "wish to punish, like some assassin, without a hearing".{{sfn|Brundage|1997|pp=144–145}}}}{{sfn|Riley-Smith|2002|pp=71–72}} The First Lateran Council later codified these privileges, placing the crusaders' "houses and households" and property under ecclesiastical protection, and ordering the excommunication of anyone seizing them. This penalty was {{Transliteration|la|latae sententiae}}, or automatic, requiring no formal trial.{{sfn|Brundage|1997|pp=146–147}} Pope {{nowrap|Eugenius III}} banned legal proceedings against crusaders and exempted them of paying interest on debts.{{sfn|Jaspert|2006|p=64}}{{sfn|Brundage|1997|p=147}} However, papal protection was not always effective: Richard I of England was imprisoned in Austria on his return from his crusade.{{sfn|Brundage|1997|pp=152–153}}

File:Innozenz3.jpg: by sanctioning the redemption of crusading vows for cash, he created a massive new source of income for crusading (a fresco in St. Benedict's Cave at the Subiaco Abbey, {{circa|1219}})]]

Crusades, underlines the historian Simon Lloyd, were "crippingly expensive", even though the precise costs of individual campaigns are rarely documented.{{refn|group=note|The first crusade of Louis IX of France stands out as a notable exception: between 1248 and 1254, he spent 1,537,570 {{Transliteration|fr|livres tournois}}—over {{nowrap|600 percent}} of his average annual income—on his campaigns in the Levant. In addition to financing his own expedition, he also supported his companions through gifts and loans, leading Lloyd to estimate Louis's total expenditure at {{circa|3,000,000}} {{Transliteration|fr|livres}}. Yet even this substantial sum excludes expenses incurred by other crusaders who joined his campaign.{{sfn|Lloyd|2002|p=53}}}}{{sfn|Lloyd|2002|p=53}} Scholars estimate that an ordinary knight spent more than four years' income to participate.{{sfn|Phillips|2014|p=24}} To finance their expeditions, wealthy crusaders often sold commodities—typically timber—or granted privileges to towns or rural communities for a lump sum.{{refn|group=note|Before departing on his crusade in 1236, Earl Richard of Cornwall ordered entire woodlands to be felled in order to sell timber. In 1202, Hugh IV, Count of Saint-Pol, granted urban privileges to three or four settlements within his domains.{{sfn|Lloyd|2002|p=55}}}} While the outright sale of inherited estates was less frequent, mortgaging family lands or transferring them in vifgage—allowing creditors to be repaid from the property's income—was common. Crusaders also relied on gifts or loans from relatives, lords, or friends.{{refn|group=note|For instance, Duke Robert Curthose pledged Normandy to his brother, King William Rufus of England, as a security for a loan of 10,000 marks in 1096.{{sfn|Mayer|2009|p=44}}}}{{sfn|Lloyd|2002|pp=54–56}} In Iberia, regular tribute extracted from Muslim rulers enabled the Christian kings to reward their vassals with stipends.{{sfn|O'Callaghan|2003|p=127}}

From the {{nowrap|mid-12th century}}, taxation became a key founding source. A special tax for the Holy Land's defence was introduced in France and England in 1166. In 1188, the "Saladin tithe"—a ten percent levy on income and property—was imposed in both kingdoms to fund the Third Crusade, though tax compliance, especially in France, was inconsistent.{{sfn|Lloyd|2002|pp=56–57}} The first papal order to tax church revenues for crusading came in 1199 under Pope {{nowrap|Innocent III}}. In 1274, Pope Gregory X detailed procedures for assessing and collecting this tax, though clergy often tried to avoid payment.{{sfn|Jotischky|2017|p=269}}{{sfn|Lloyd|2002|pp=57–58}} From 1199, donations were collected via chests placed in churches.{{sfn|Lloyd|2002|p=58}} In 1213, Pope {{nowrap|Innocent III}} introduced a novel fundraising mechanism, authorising everybody—except monks—to take a crusade vow, but also permitting them to redeem it through a cash payment.{{sfn|Lloyd|2002|pp=48, 58}}{{sfn|Tyerman|2019|p=238}} Purchasing indulgences remained the most common form of crusading into the early modern period, despite their high cost.{{refn|group=note|In Germany, an indulgence cost roughly the equivalent of a household's weekly expenses {{circa|1500}}.{{sfn|Tyerman|2019|p=425}}}} As printing technology spread from the {{nowrap|mid-15th-century}}, indulgence sheets were mass-produced with blanks for beneficiaries' names.{{sfn|Tyerman|2019|p=425}}

{{See also|List of Crusader castles}}

Command during most crusades was divided and uncertain, and desertion from the armies was not uncommon.{{sfn|France|1999|pp=208–210}} Yet crusader morale was often boosted by visions, processions, and relics.{{refn|group=note|Between 1099 and 1187, the Jerusalemite army carried the True Cross—a relic linked to Christ’s crucifixion—into {{nowrap|31 battles}}.{{sfn|Phillips|2014|pp=142–143}}}}{{sfn|Phillips|2014|pp=142–143}}{{sfn|Tyerman|2019|pp=92–93}} Raids and battles were central to warfare in both Western Europe and the Middle East, but for most crusaders, besieging fortified urban centres—a standard feature of Levantine warfare—was unfamiliar. Raids primarily aimed at booty, destruction, or preparing major invasions.{{sfn|Phillips|2014|p=96}} Crusaders generally avoided pitched battles, as defeat could result in devastating losses of troops and territory.{{refn|group=note|The Franks suffered catastrophic defeats at Harran (1104), on the Field of Blood (1119), and at Harim (1164) in Syria, and at Pelagonia (1259) and at Halmyros (1311) in Frankish Greece.{{sfn|Phillips|2014|p=97}}{{sfn|Lock|1995|pp=91, 106}} In the north, the Lithuanians' victory over the Sword Brothers at Saule annihilated the Brothers' power.{{sfn|Christiansen|1997|p=102}}}}{{sfn|Phillips|2014|p=97}} Siege warfare relied heavily on stone-throwing engines, siege towers and battering rams. Muslim defenders often employed Greek fire, but crusaders learnt to counter it using hides soaked in vinegar.{{sfn|Phillips|2014|pp=105–106}} From the late {{nowrap|13th century}}, most plans for the recovery of the Holy Land distinguished two types of campaigns: a preliminary {{transliteration|la|passagium particulare}} for establishing a bridgehead for the large-scale {{transliteration|la|passagium generale}}.{{sfn|Tyeran|2019|p=379}}

Knights, the core of crusader armies, were heavily armoured horsemen.{{sfn|Phillips|2014|p=98}} The historian John France describes them as the "masters of close-quarter warfare". In the east, they primarily faced mounted archers and relied on infantry support, particularly bowmen and spearmen.{{sfn|France|1999|p=219}} The Franks also hired native light cavalrymen, or Turcopoles, to harass and capture enemy troops.{{sfn|France|1999|pp=219–220}} In the north, Teutonic Knights employed converted Prussians to raid pagan settlements.{{sfn|Christiansen|1997|p=100}} Almogavars—Spanish raiders—mainly used daggers, short lances and darts.{{sfn|O'Callaghan|2003|p=129}}

Naval force for Levantine crusades were chiefly suplied by Italian city-states and the Byzantines. Egypt maintained the only Muslim fleet in the eastern Mediterranean, but its small ships rarely threatened Western naval dominance. After Emperor {{nowrap|Frederick I}}'s failed overland crusade, all subsequent Levantine campaigns were transported by sea.{{sfn|France|1999|p=207}} In the north, large Scandinavian and German merchant vessels, capable of carrying {{nowrap|500 people}}, easily overcame the Baltic peoples' raiding-crafts and long-ships.{{sfn|Christiansen|1997|p=91}}

Across all territories conquered by the crusaders, castles were constructed to function as both military bases and administrative centres. These fortifications often blended Western European engineering with local building traditions. In the Levant, Norman-style fortified towers were initially built, but the Franks soon adopted the local {{Transliteration|la|castra}} layout of walled courtyards. This evolved into concentric castles with dual defensive systems, capable of withstanding sieges for months.{{refn|group=note|Montreal Castle, built in 1115, represents the earliest instance of the Franks adapting the local {{Transliteration|la|castra}} form. The concentric castle design was implemented later, with the construction of Belvoir Castle in 1168.{{sfn|Tyerman|2019|pp=142–143}}}}{{sfn|Tyerman|2019|p=142}}{{sfn|Phillips|2014|pp=104–105}} Built on rocky hilltops, and heavily fortified with towers and a keep, spur castles represent "the most spectacular examples of Frankish military architecture", according to Phillips.{{refn|group=note|Saone Castle in the Principality of Antioch, Kerak Castle in the Kingdom of Jerusalem, and Crac des Chevaliers in the County of Tripoli are among the best known examples of spur castles.{{sfn|Phillips|2014|pp=104–105}}}}{{sfn|Phillips|2014|p=104}} In Iberia, over {{nowrap|2,000 castles}} were built on frontier promontories, enabling their garrisons to monitor enemy movement.{{sfn|O'Callaghan|2003|pp=124–125}} The Teutonic Knights first raised blockhouses to defend their Baltic territories, but by {{circa|1250}} began consructing stone towers. In the {{nowrap|14th century}}, stone was largely replaced by cheaper, more readily available brick.{{sfn|Christiansen|1997|pp=67}}

{{Main|Military order (religious society)}}

File:SCONTRO A NABLUS - AFFRESCHI CONTROFACCIATA S. BEVIGNATE.JPG from San Bevignate depicting the Templars battling Muslim warriors]]

Tyerman argues that the military orders "provided crusading's most original contribution to the institutions of medieval Christendom". These religious orders followed monastic rules but were dedicated to fighting for fellow Christians.{{sfn|Tyerman|2019|pp=151–152}}{{sfn|Forey|2002|pp=176–177}} The first military order was initiated by the French knight Hugues de Payens and his companions who decided to protect pilgrims in the Holy Land. In 1119, they took the three monastic vows of chastity, poverty and obedience, forming a confraternity. Official recognition came in 1120, and they became known as the Knights Templar after King Baldwin II of Jerusalem granted them chambers in the former Al-Aqsa Mosque, associated with the Temple of Solomon.{{sfn|Madden|2013|p=46}}{{sfn|Tyerman|2019|pp=152–154}}

The concept of warrior-monks was revolutionary yet aligned with contempory chivalric and ecclesiastical ideals.{{sfn|Phillips|2014|p=67}} By {{circa|1130}}, Bernard of Clairvaux praised the Templars as a "new knighthood".{{sfn|Tyerman|2019|p=154}} The Templars inspired other groups, primarily in borderlands of Latin Christianity.{{sfn|Forey|2002|p=178}} In the Holy Land, the militarisation of nursing confraternities led to the formation of military orders—the Knights Hospitaller, the Teutonic Knights, the Knights of Saint Thomas, and the Lazarists.{{sfn|Tyerman|2019|pp=154–156}}{{sfn|Forey|2002|p=178}} In Iberia, royal support helped to establsh the Orders of Calatrava, Santiago, Alcántara and Aviz. In the Baltic, the Sword Brothers and Order of Dobrzyń, founded by local bishops, merged into the Teutonic Order by 1230.{{sfn|Jaspert|2006|pp=148–150}}{{sfn|Forey|2002|pp=179–180}} The papacy endorsed the Iberian and Baltic crusades by granting crusade indulgences to participants in campaigns lanched by the Orders of Alcántara (1238), Calatrava (1240), or the Teutonic Knights (1245).{{sfn|Tyerman|2019|p=300}}{{sfn|Christiansen|1997|p=83}}

Military orders were organised by function: the knight-brothers and {{lang|la|servientes}} were armed monks; priest-brothers handled spiritual care; nobles could temporarily join for spiritual rewards; and others supported the order financially.{{sfn|Jaspert|2006|pp=155–156}} The Templars and Hospitallers became the most powerful, owning estates across Latin Christendom and evolving into autonomous international organisation led by elected grand masters.{{sfn|Jotischky|2017|pp=83–90}}{{sfn|Jaspert|2006|p=157}} Their convent networks facilitated the transfer of goods and cash, with the Templars becaming mayor players in money markets.{{sfn|Forey|2002|pp=191–192}} Time to time, clerics and scholars criticised the military orders for greed, pride, and adopting non-Christian customs.{{sfn|Jaspert|2006|p=162}}

With the fall of the Crusader states, many military orders lost their justification for existence, intensifying criticism against them. The Templars faced particularly harsh scrutiny, as fighting Muslims was their sole purpose.{{sfn|Jaspert|2006|pp=162–163}} In 1307, all Templars were arrested in France on charges of apostasy, idolatry and sodomy by order of King Philip IV. Despite no physical evidence supporting the accusations, the Order was dissolved without a hearing at the Council of Vienne in 1312.{{sfn|Forey|2002|pp=208–210}} The Hospitallers survived, assuming responsibility for protecting shipping in the Mediterranean. Despite secularisation during the Reformation, the Teutonic Knights endured in Germany under Habsburg leadership. Iberian military orders gradually lost their religious character, as they affiliated with the Spanish and Portuguese Crowns, receiving papal dispensations from monastic obligations.{{sfn|Luttrell|2002|pp=333–338, 344–345, 350–358}}

{{Main|Crusader states|Kingdom of Cyprus|Frankokratia|State of the Teutonic Order|Hospitaller Rhodes|Hospitaller Malta}}

The four Crusader states secured Catholic control of the Holy Land, sustained by military and financial support from Catholic Europe. Edessa, the earliest and most vulnerable, fell after a misguided alliance with Zengi's Muslim rivals, the Artuqids.{{sfn|Jotischky|2017|p=83}} Internal factionalism weakened Jerusalem, leaving it unable to resist Saladin's 1187 invasion, though the Third Crusade restored Frankish control along the coast.{{sfn|Jotischky|2017|pp=103–110}}{{sfn|Phillips|2002|p=132}} In the north, Antioch and Tripoli formed a personal union following the War of the Antiochene Succession.{{sfn|Phillips|2002|p=135}} After {{nowrap|Frederick II}}'s crusade, absent kings left Jerusalem governed by regents, sometimes chosen by their opponents.{{sfn|Jaspert|2006|p=88}} By the Mamluk advance, the Crusader states had splintered into warring autonomous communities led by Frankish lords, urban communes, Italian merchants, and military orders.{{sfn|Jaspert|2006|pp=94–95}}

File:Bellapais Hof ohne Baum.jpg in Cyprus]]

Just a day's sail from Syria, Cyprus became a key supply base for Levantine crusades and a refuge for mainland exiles.{{sfn|Phillips|2002|pp=125–129}} From 1269, its kings also claimed Jerusalem, though the Sicilian Angevins contested this from 1277.{{sfn|Lock|2006|pp=116, 119}} The Black Death struck in 1347–48; soon, shifting trade routes weakened its main port, Famagusta. Peter I of Cyprus launched a crusade against Alexandria, Famagusta's Egyptian rival, threatening Genoese trade. In response, the Genoese sacked Famagusta and imposed tribute on Cyprus. Later, the island became a corsair haven, prompting the Mamluk invasion in 1426. After the Lusignan line ended in 1474, the Venetians assumed control, but lost the island to the Ottomans in 1570-71.{{sfn|Edbury|2002|pp=294–298}}

Months before Constantinople's sack, the leaders of the Fourth Crusade agreed to partition the Byzantine Empire: an elected emperor would receive a quarter of the territory, the rest going to other Frankish leaders and Venice.{{sfn|Jotischky|2017|p=182}}{{sfn|Phillips|2002|p=129}} Frankish Greece proved more stable than the Crusader states and attracted more Western settlers.{{sfn|Phillips|2002|p=129}} Rising demand for goods such as wheat, olive oil and silk enriched the Frankish lords of the Peloponnese, turning the court of the Villehardouin princes of Achaea into a center of chivalric life.{{sfn|Phillips|2002|p=131}}{{sfn|Jotischky|2017|p=226}} Achaea survived the Byzantine restoration in Constantinople under Angevin protection; it was annexed to the Greek Despotate of the Morea in 1430. Achaea's former vassal, the Duchy of Athens was seized by mutinous Catalan mercenaries in 1311, and later by the Acciaioli, a Florentine banking dynasty, in 1388. Their final stronghold, Thebes fell to the Ottomans in 1460.{{sfn|Edbury|2002|pp=299–304}} Though the Ottomans challenged Venetian naval power, Venice held positions in the "Realm of Candia" into the early {{nowrap|18th century}}.{{sfn|Edbury|2002|pp=307–310}}

The State of the Teutonic Order originated {{circa|1225}}, when Duke Konrad I of Masovia offered Kulmerland in Prussia to the Knights. Within a decade, imperial, ducal and papal documents secured their independent claim to the region and future conquests. In 1237, they gained Livonian lands through the merger with the Sword Brothers.{{sfn|Christiansen|1997|pp=82–83, 103}} After the Crusader states collapsed, the Order shifted its focus entirely to the Baltic region, relocating the grand masters' headquarters to Malbork in 1309.{{sfn|Forey|2002|p=208}} To consolidate control, the Order attracted German nobles, burghers and peasants to the region by offering generous privileges.{{sfn|Christiansen|1997|pp=213–216}} After Tannenberg, Polish invasions and internal conflict devastated Prussia, and by 1438 the grand master had lost influence over the leadership of the Order's Livonian branch.{{sfn|Luttrell|2002|pp=333, 343}} Prussia was transformed into a Protestant duchy in 1525, and Livonia in 1561.{{sfn|Christiansen|1997|pp=246–247, 257}}

The Hospitallers conquered the island of Rhodes from the Byzantines in 1306–1309.{{sfn|Edbury|2002|p=298}} Though limited in size and resources, Rhodes was heavily fortified using income from the Hospitallers' overseas estates.{{sfn|Luttrell|2002|p=334}} The island resisted Mamluk and Ottoman invasions, but was taken by the Ottoman Sultan {{nowrap|Suleiman II}} in 1522.{{sfn|Edbury|2002|p=299}} In 1530, the Hospitallers received the Mediterranean islands of Malta and Gozo in fief from Emperor {{nowrap|Charles V}}.{{sfn|Luttrell|2002|p=347}} They withstood the 1565 Great Siege of Malta, and only lost the island to Napoleon Bonaparte in 1798.{{sfn|Luttrell|2002|pp=348, 356–357}}

{{Main|Criticism of crusading}}

Opponents of the Gregorian Reform (such as the scholar Sigebert of Gembloux) condemned the concept of penitential warfare, but their voice lost in the euphoria raised by the successful First Crusade.{{sfn|Riley-Smith|2002|pp=79–80}} Mainstream criticism of crusading initially focused on certain aspects of the movement, like the risks of a crusader's absence from their home.{{sfn|Jaspert|2006|p=69}} The existence of military orders was unacceptable for those who regarded monastic life incompatible with knighthood.{{sfn|Phillips|2014|p=71}} Millenarian thinkers, like Joachim of Fiore, regarded the crusades as phenomena of a passing period, stating that the Muslims' voluntary conversion to Christianity would introduce a new age sometime soon.{{sfn|Jaspert|2006|p=71}}

The geographical expansion of the crusades attracted a new wave of criticism because many thought that crusades against Christians in Europe distracted attention from the Holy Land.{{refn|group=note|Guilhem Figueira, a famous troubadour, blamed the papacy for the failure of the Fifth Crusade at Damietta, stating that the Holy See had offered a "false pardon" to the French crusaders when declaring the Albigensian Crusades.{{sfn|Routledge|2002|p=109}}}}{{sfn|Jaspert|2006|p=69}} Some Occitan troubadours went as far as associating the northern French crusaders invading Occitania with the Muslims menacing the Holy Land.{{sfn|Routledge|2002|pp=108–109}} The complete failure of the crusades for the Holy Land after the {{nowrap|mid-13th century}} prompted the chronicler Salimbene di Adam to state that attempts to recover the Palestinian holy places did not enjoy divine support. Others argued that the Christians were unable to overcome the Muslims in the Levant due to demographic disparity, or emphasised that the crusades prevented effective proselytism among Muslims. The Dominican friar Humbert of Romans compiled a whole study against similar arguments in 1274.{{sfn|Jaspert|2006|pp=69–70}}

• History of Christianity
• Religious violence
• Christianity and violence

{{Reflist|group=note}}

{{Reflist|20em}}

{{refbegin|30em}}

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• {{cite book|last=Tyerman|first=Christopher|year=2011|title=The Debate on the Crusades, 1099–2010|series=Issues in Historiography|url=https://manchesteruniversitypress.co.uk/9780719073212/|publisher=Manchester University Press|isbn=978-0-7190-7320-5}}
• {{cite book|last=Tyerman|first=Christopher|year=2019|title=The World of the Crusades: An Illustrated History|publisher=Yale University Press|url=https://yalebooks.yale.edu/book/9780300274219/the-world-of-the-crusades/|isbn=978-0-3002-1739-1}}

{{refend}}

{{refbegin|30em}}

• {{cite book|last=Cobb|first=Paul M.|title=The Race for Paradise : an Islamic History of the Crusades|publisher=Oxford University Press|year=2014|ref=none}}
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• {{cite journal|last1=Horowitz|first1=Michael C.|title=Long Time Going:Religion and the Duration of Crusading|journal=International Security|date=2009|volume=34|issue=27|pages=162–193|jstor=40389216|url=https://www.jstor.org/stable/40389216|publisher=MIT Press|doi=10.1162/isec.2009.34.2.162|s2cid=57564747|ref=none|access-date=2022-08-16|archive-date=2022-08-16|archive-url=https://web.archive.org/web/20220816082248/https://www.jstor.org/stable/40389216|url-status=live|url-access=subscription}}
• {{cite journal|last=Kedar|first=Benjamin Z.|title=Crusade Historians and the Massacres of 1096|journal=Jewish History|volume=12|issue=2|year=1998|pages=11–31|doi=10.1007/BF02335496|s2cid=153734729|ref=none}}
• {{cite book|last=Kostick|first=Conor|title=The Social Structure of the First Crusade|publisher=Brill|year=2008|ref=none}}
• {{cite book|last=Maier|first=C.|year=2000|title=Crusade Propaganda and Ideology: Model Sermons for the Preaching of the Cross|publisher=Cambridge University Press|doi=10.1017/CBO9780511496554|isbn=978-0-521-59061-7|ref=none}}
• {{cite book|last=Polk|first=William R.|title=Crusade and Jihad: The Thousand-Year War Between the Muslim World and the Global North|publisher=Yale University Press |year=2018|ref=none}}
• {{cite book|last=Riley-Smith|first=Jonathan|chapter=The crusading movement|pages=127–140|editor1-last=Hartmann|editor1-first=Anja V.|editor2-last=Hauser|editor2-first=Beatrice|title=War, Peace and World Orders in European History|year=2001|publisher=Routledge|isbn=978-0-415-24440-4|ref=none}}
• {{cite book|last=Tuck|first=Richard|year=1999|title=The Rights of War and Peace: Political Thought and the International Order from Grotius to Kant|publisher=Oxford University Press|isbn=978-0-19-820753-5|url=https://books.google.com/books?id=d3RYAwAAQBAJ|ref=none}}
• {{cite journal |last1=Tyerman|first1=Christopher|author-link=Christopher Tyerman|title=Were There Any Crusades in the Twelfth Century?|journal=The English Historical Review|date=1995|volume=110|issue=437|pages=553–577|jstor=578335|publisher=Oxford University Press|doi=10.1093/ehr/CX.437.553|ref=none|doi-access=free}}

{{refend}}

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