SMS Posen

{{Main|Nassau-class battleship}}

Design work on the {{lang|de|Nassau}} class began in late 1903 in the context of the Anglo-German naval arms race; at the time, battleships of foreign navies had begun to carry increasingly heavy secondary batteries, including Italian and American ships with {{cvt|20.3|cm|0}} guns and British ships with {{cvt|23.4|cm}} guns, outclassing the previous German battleships of the {{sclass|Deutschland|battleship|4}} with their {{cvt|17|cm}} secondaries. German designers initially considered ships equipped with {{cvt|21|cm}} secondary guns, but erroneous reports in early 1904 that the British {{sclass|Lord Nelson|battleship|1}}s would be equipped with a secondary battery of {{cvt|25.4|cm|0}} guns prompted them to consider an even more powerful ship armed with an all-big-gun armament consisting of eight {{cvt|28|cm}} guns. Over the next two years, the design was refined into a larger vessel with twelve of the guns, by which time Britain had launched the all-big-gun battleship {{HMS|Dreadnought|1906|6}}.{{sfn|Dodson|pp=72–75}}

File:Nassau-class plan and profile.png

{{lang|de|Posen}} was {{convert|146.1|m|ft|abbr=on}} long, {{convert|26.9|m|ftin|abbr=on|1}} wide, and had a draft of {{convert|8.9|m|ftin|abbr=on|1}}. She displaced {{convert|18,873|t|LT|sp=us|lk=on}} with a standard load, and {{convert|20,535|t|LT|abbr=on}} fully laden.{{efn|According to Erich Gröner, this figure is calculated as "25 to 50 percent full load...and [was] used in the German navy since 1882 as a basis for performance and speed calculations."{{sfn|Gröner|p=ix}}}} She had a flush deck and a ram bow, a common feature for warships of the period. {{lang|de|Posen}} had a fairly small superstructure, consisting primarily of forward and aft conning towers. She was fitted with a pair of pole masts for signaling and observation purposes. The ship had a crew of 40 officers and 968 enlisted men.{{sfn|Gröner|p=23}}{{sfn|Campbell & Sieche|p=140}}

{{lang|de|Posen}} retained 3-shaft triple expansion engines instead of the more advanced turbine engines. Steam was provided to the engines by twelve coal-fired water-tube boilers, which were vented through two funnels. Her propulsion system was rated at {{convert|22000|PS|ihp kW|lk=on}} and provided a top speed of {{convert|20|kn|lk=in}}. She had a cruising radius of {{convert|8300|nmi|lk=in}} at a speed of {{convert|12|kn}}.{{sfn|Gröner|p=23}}{{sfn|Campbell & Sieche|p=140}}{{efn|This type of machinery was chosen at the request of both Admiral Alfred von Tirpitz and the Navy's construction department; the latter stated in 1905 that the "use of turbines in heavy warships does not recommend itself."{{sfn|Herwig|pp=59–60}} This decision was based solely on cost: at the time, Parsons held a monopoly on steam turbines and required a 1 million gold mark royalty fee for every turbine engine made. German firms were not ready to begin production of turbines on a large scale until 1910.{{sfn|Staff Vol. 1|pp=23, 35}}}}

{{lang|de|Posen}} carried a main battery of twelve 28 cm SK L/45 gun{{efn|In Imperial German Navy gun nomenclature, "SK" ({{lang|de|Schnelladekanone}}) denotes that the gun is quick firing, while "L/45" provides the length of the gun in terms of the diameter of the barrel. In this case, the L/45 gun is 45 calibers, which means that the gun is 45 times as long as its diameter.{{sfn|Grießmer|p=177}}}} guns in six gun turrets arranged in an unusual hexagonal configuration. One was placed forward, another toward the stern, and the remaining four were placed on the wings, two per broadside. Her secondary armament consisted of twelve 15 cm SK L/45, mounted in casemates located amidships. Close-range defense against torpedo boats was provided by a tertiary battery of sixteen 8.8 cm SK L/45 naval gun, which were also mounted in casemates.{{sfn|Gröner|p=23}} Later in her career, two of the 8.8 cm guns were replaced with high-angle Flak mountings of the same caliber for defense against aircraft.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|p=239}} The ship was also armed with six {{convert|45|cm|in|abbr=on|1}} submerged torpedo tubes. One tube was mounted in the bow, another in the stern, and two on each broadside, on either ends of the torpedo bulkhead.{{sfn|Campbell & Sieche|p=140}}

The ship's hull was protected by heavy armor plate consisting of Krupp cemented steel. The belt armor along the sides of the hull was {{cvt|11.5|in|cm|order=flip}} thick in the central portion, tapering down to {{cvt|4|in|cm|order=flip}} at the bow. The belt was reinforced by an armored deck that angled downward at the sides to connect to the bottom edge of the belt. The deck was {{cvt|1.5|in|cm|order=flip}} on the flat portion, while the sloped sides increased in thickness to {{cvt|2.3|in|cm|order=flip}}. {{lang|de|Posen}}{{'}}s main battery turrets had 28 cm of Krupp steel on their faces. Her forward conning tower had {{cvt|30|cm|1}} of armor plate on the sides, while the aft tower received only {{cvt|20|cm|1}} on the sides.{{sfn|Gröner|p=23}}{{sfn|Campbell 1977|pp=13–14}}

File:First and second battleship squadrons and small cruiser of the - NARA - 533188-2 restored.jpg in Kiel before the war]]

{{lang|de|Posen}} was ordered under the provisional name {{lang|de|Ersatz Baden}}, as a replacement for the {{SMS|Baden|1880|2}}, one of the elderly {{sclass|Sachsen|ironclad|2}}s.{{sfn|Gröner|p=23}} She was laid down on 11 June 1907 at the Germaniawerft shipyard in Kiel.{{sfn|Staff Vol. 1|p=20}} As with her sister {{SMS|Nassau||2}}, construction proceeded under absolute secrecy; detachments of soldiers guarded the shipyard and also guarded contractors that supplied building materials, such as Krupp.{{sfn|Hough|p=26}} The ship was launched a year and a half later, on 12 December 1908.{{sfn|Staff Vol. 1|p=20}} Wilhelm August Hans von Waldow-Reitzenstein, the president of the ship's namesake province gave a speech at her launching, and {{lang|de|Posen}} was christened by Johanna von Radolin, the wife of Hugo Fürst von Radolin, a German diplomat who hailed from Posen. Initial trials were conducted through April 1910, followed by final fitting-out in May. The ship was commissioned into the fleet on 31 May, under the command of {{lang|de|Kapitän zur See}} (KzS—Captain at Sea) Otto Back. Sea trials were conducted afterward and completed by 27 August.{{sfn|Staff Vol. 1|p=32}}{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|p=239}} In total, her construction cost the German government 36,920,000 marks.{{sfn|Gröner|p=23}}

After completing her trials in August 1910, {{lang|de|Posen}} left Kiel for Wilhelmshaven, where she arrived on 7 September. As the German Imperial Navy had chronic shortages of trained sailors,{{sfn|Herwig|p=90}} many of the crew were then assigned to other ships.{{sfn|Staff Vol. 1|p=32}}{{efn|Of the problem, Admiral Iwan Oldekop stated in November 1912: "There is almost no more personnel on land. Garrison watch duty can no longer be conducted according to regulations...The Navy units [in Kiel] are equally exhausted as in Wilhelmshaven. Complaints concerning lack of personnel on land are the same."{{sfn|Herwig|p=90}}}} These crewmembers were replaced with personnel from the old pre-dreadnought battleship {{SMS|Wittelsbach||2}}, which was decommissioned on 20 September. After their commissioning, all four {{lang|de|Nassau}}-class ships served as a unit, II Division of I Battle Squadron, with {{lang|de|Posen}} as the divisional flagship. The ships participated in a training cruise in the Baltic Sea late in 1910.{{sfn|Staff Vol. 1|pp=11, 32}}

Over the next four years, {{lang|de|Posen}} participated in several training exercises with the rest of the fleet before the outbreak of war.{{sfn|Staff Vol. 1|p=32}} In 1911, {{lang|de|Konteradmiral}} (Rear Admiral) Karl Zimmermann hoisted his flag aboard Posen.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|p=240}} In March that year, the fleet conducted exercises in the Skagerrak and Kattegat, and further exercises were held in May. {{lang|de|Posen}} and the rest of the fleet received British and American naval squadrons at Kiel in June and July, after which the fleet took its annual summer cruise to Norway. The year's autumn maneuvers were confined to the Baltic and the Kattegat. Another fleet review was held afterward, during the exercises for a visiting Austro-Hungarian delegation that included Archduke Franz Ferdinand and Admiral Rudolf Montecuccoli.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 2|pp=241–242}}{{sfn|Staff Vol. 1|p=8}}

The next year followed a similar pattern until mid-1912, when the summer cruise was confined to the Baltic due to the Agadir Crisis; the naval command sought to avoid exposing the fleet during the period of heightened tension with Britain and France. The September exercises were conducted off Helgoland in the North Sea; the following month, KzS Richard Lange relieved Back as the ship's commander. Another winter cruise into the Baltic followed at the end of the year. The training program for 1913 proceeded in much the same pattern as in previous years.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|p=239}}{{sfn|Staff Vol. 1|p=8}}{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 2|pp=242–243}} The training schedule returned to normal for 1913 and 1914, and the summer cruises again went to Norway. For the 1914 cruise, the fleet departed for Norwegian waters on 14 July, some two weeks after the assassination of Archduke Franz Ferdinand in Sarajevo. The probability of war cut the cruise short; {{lang|de|Posen}} and the rest of the fleet were back in Wilhelmshaven by 29 July.{{sfn|Staff Vol. 1|p=11}}

File:SMS Posen sketch by Oscar Parkes.jpg]]

At midnight on 4 August, the United Kingdom declared war on Germany.{{sfn|Herwig|p=144}} {{lang|de|Posen}} and the rest of the fleet conducted several advances into the North Sea to support Rear Admiral Franz von Hipper's I Scouting Group battlecruisers.{{sfn|Staff Vol. 1|p=32}} The battlecruisers raided British coastal towns in an attempt to lure out portions of the Grand Fleet where they could be destroyed by the High Seas Fleet.{{sfn|Herwig|pp=149–150}} The first such operation was the raid on Scarborough, Hartlepool and Whitby on 15–16 December 1914.{{sfn|Tarrant|p=31}} On the evening of 15 December, the German battle fleet of 12 dreadnoughts—including {{lang|de|Posen}} and her three sisters—and eight pre-dreadnoughts came to within {{convert|10|nmi|abbr=on}} of an isolated squadron of six British battleships. Skirmishes between the rival destroyer screens in the darkness convinced the German fleet commander, Admiral Friedrich von Ingenohl, that he was faced with the Grand Fleet, now deployed in its battle formation. Under orders from Kaiser Wilhelm II to avoid risking the fleet unnecessarily, Ingenohl broke off the engagement and turned the battlefleet back toward Germany.{{sfn|Tarrant|pp=31–33}}

{{lang|de|Posen}} next took part in the fleet advance on 24 January 1915 to support I Scouting Group after it had been ambushed by the British 1st and 2nd Battlecruiser Squadrons during the Battle of Dogger Bank, though she again saw no action, as the battle had ended before the High Seas Fleet arrived late in the afternoon.{{sfn|Massie|pp=375–404}} Following the loss of the armored cruiser {{SMS|Blücher}} at the Battle of Dogger Bank, the Kaiser removed Ingenohl from his post on 2 February. Admiral Hugo von Pohl replaced him as commander of the fleet.{{sfn|Tarrant|pp=43–44}} Pohl conducted a series of fleet advances in 1915 in which {{lang|de|Posen}} took part; in the first one on 29–30 March, the fleet steamed out to the north of Terschelling and return without incident. Another followed on 17–18 April, where the fleet covered a mining operation by II Scouting Group. Three days later, on 21–22 April, the High Seas Fleet advanced towards the Dogger Bank, though again failed to meet any British forces.{{sfn|Staff Vol. 2|p=15}} In mid-May, {{lang|de|Posen}} entered the shipyard for periodic maintenance, which was completed in time for the next fleet operation.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|p=240}} The fleet next went to sea on 29–30 May, advancing as far as Schiermonnikoog before being forced to turn back by inclement weather. On 10 August, the fleet steamed to the north of Helgoland to cover the return of the auxiliary cruiser {{SMS|Meteor|1914|2}}.{{sfn|Staff Vol. 2|p=15}}

{{main|Battle of the Gulf of Riga}}

In August 1915, a special unit from the German fleet attempted to clear the Russian-held Gulf of Riga in order to assist the German Army, which was planning an assault on Riga. To do so, the German planners intended to drive off or destroy the Russian naval forces in the Gulf, which included the pre-dreadnought battleship {{ship|Russian battleship|Slava||2}} and some smaller gunboats and destroyers. The German battle fleet was accompanied by several mine-warfare vessels. These ships were tasked with clearing Russian minefields and laying a series of their own minefields in the northern entrance to the gulf, to prevent Russian naval reinforcements from reaching the area. The assembled German flotilla included {{lang|de|Posen}} and her three sister ships, the four {{sclass|Helgoland|battleship|2}}s, the battlecruisers {{SMS|Von der Tann||2}}, {{SMS|Moltke||2}}, and {{SMS|Seydlitz||2}}, and several pre-dreadnoughts, operating under the command of Hipper, now a vice admiral. The eight battleships were to provide cover for the forces engaging the Russian flotilla. The first attempt on 8 August was unsuccessful, as it had taken too long to clear the Russian minefields to allow the minelayer {{SMS|Deutschland|1914|2}} to lay a minefield of her own.{{sfn|Halpern|pp=196–197}}

The Germans planned a second attempt, and on 15 August, the overall naval commander of the operation—{{lang|de|Vizeadmiral}} Ehrhard Schmidt—made {{lang|de|Posen}} his flagship.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|pp=240–241}} {{lang|de|Posen}} and {{lang|de|Nassau}} led the second attempt to breach the defenses of the gulf the following day.{{sfn|Staff Vol. 1|p=32}} The two dreadnoughts were accompanied by 4 light cruisers and 31 torpedo boats. On the first day of the assault the Germans broke through the Russian forces, but two German light craft—the minesweeper {{SMS|T46||2}} and the destroyer {{SMS|V99||2}}—were sunk.{{sfn|Halpern|p=197}} {{lang|de|Posen}} and {{lang|de|Nassau}} engaged a pair of Russian gunboats, {{ship|Russian gunboat|Sivuch|1907|2}} and {{ship|Russian gunboat|Korietz||2}}. {{lang|ru|Sivuch}} was sunk that day and {{lang|ru|Korietz}} was severely damaged; the ship managed to limp away but had to be scuttled the following day.{{sfn|Staff Vol. 1|p=32}} On the 17th, {{lang|de|Posen}} and {{lang|de|Nassau}} engaged {{lang|ru|Slava}} at long range; they scored three hits on the Russian ship and forced her to return to port. By 19 August, the Russian minefields had been cleared and the flotilla entered the Gulf. Reports of Allied submarines in the area prompted the Germans to call off the operation the following day.{{sfn|Halpern|pp=197–198}}

Hipper later remarked, "To keep valuable ships for a considerable time in a limited area in which enemy submarines were increasingly active, with the corresponding risk of damage and loss, was to indulge in a gamble out of all proportion to the advantage to be derived from the occupation of the Gulf before the capture of Riga from the land side." In fact, the battlecruiser {{lang|de|Moltke}} had been torpedoed that morning.{{sfn|Halpern|p=198}} On 21 August, Schmidt had his flag hauled down from {{lang|de|Posen}} and disbanded the special unit.{{sfn|Staff Vol. 1|p=32}} The operation nevertheless achieved significant strategic goals, since it reduced the Russian naval command's desire to deploy its few modern warships into the central Baltic, and the threat of future German amphibious operations led the Russian Army to withdraw the Guards Corps from the fighting on the Eastern Front to defend Estonia.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|p=241}}

File:SMS Westfalen LOC 25466u.jpg

By the end of August {{lang|de|Posen}} and the rest of the High Seas Fleet had returned to their anchorages in the North Sea. The next operation conducted was a sweep into the North Sea on 11–12 September, though it ended without any action. Another fleet sortie followed on 23–24 October without encountering any British forces.{{sfn|Staff Vol. 1|p=31}} On 12 January 1916, Admiral Reinhard Scheer replaced Pohl as the fleet commander; Scheer continued the aggressive fleet strategy of his predecessors.{{sfn|Staff Vol. 2|p=15}} On 4 March 1916, {{lang|de|Posen}}, {{lang|de|Nassau}}, {{lang|de|Westfalen}}, and {{lang|de|Von der Tann}} steamed out to the Amrumbank to receive the auxiliary cruiser {{SMS|Möwe|1914|2}}, which was returning from a raiding mission.{{sfn|Staff Vol. 1|p=33}} {{lang|de|Nassau}} was present during the fleet advance on 5–7 March, though this too ended without action. Further sorties were conducted on 26 March, 2–3 April, and 21–22 April, but none resulted in action with British forces.{{sfn|Staff Vol. 2|p=15}} A bombardment mission followed two days later; {{lang|de|Westfalen}} joined the battleship support for Hipper's battlecruisers while they attacked Yarmouth and Lowestoft on 24–25 April.{{sfn|Staff Vol. 1|p=31}} During this operation, the battlecruiser {{lang|de|Seydlitz}} was damaged by a British mine and had to return to port prematurely. Due to poor visibility, the operation was soon called off, leaving the British fleet no time to intercept the raiders.{{sfn|Tarrant|pp=52–54}}

{{main|Battle of Jutland}}

File:Map of the Battle of Jutland, 1916.svg

Scheer immediately planned another attack on the British coast after the failed attempt against Yarmouth. The damage to {{lang|de|Seydlitz}} and condenser trouble on several of the III Battle Squadron dreadnoughts delayed the plan until the end of May.{{sfn|Tarrant|pp=56–58}} The German battlefleet departed the Jade at 03:30 on 31 May.{{sfn|Tarrant|p=62}} {{lang|de|Posen}} was assigned to II Division of I Battle Squadron as the flagship of Rear Admiral W. Engelhardt. {{lang|de|Posen}} was the first ship in the division, ahead of her three sisters. II Division was the last unit of dreadnoughts in the fleet; they were followed by only the elderly pre-dreadnoughts of II Battle Squadron.{{sfn|Tarrant|p=286}}

Between 17:48 and 17:52, {{lang|de|Posen}} and ten other German battleships engaged the British 2nd Light Cruiser Squadron, though the range and poor visibility prevented effective fire.{{sfn|Campbell 1998|p=54}} Shortly thereafter, two British destroyers—{{HMS|Nomad||2}} and {{HMS|Nestor|1915|2}}—came under intense fire from the German line. {{lang|de|Posen}} fired at Nestor with both her main battery and secondary guns. At 18:35, Nestor exploded and sank under the combined fire of eight battleships.{{sfn|Campbell 1998|p=101}} By 20:15, the German fleet had faced the Grand Fleet for a second time and was forced to turn away; in doing so, the order of the German line was reversed. {{lang|de|Posen}} was now the fourth ship in the line, astern of her three sisters.{{sfn|Tarrant|p=172}}

At around 21:20, {{lang|de|Posen}} and her sister ships were engaged by the battlecruisers of the 3rd Battlecruiser Squadron. {{lang|de|Posen}} was the only ship of I Battle Squadron to be able to make out a target, which turned out to be the battlecruisers {{HMS|Princess Royal|1911|6}} and {{HMS|Indomitable|1907|2}}. {{lang|de|Posen}} opened fire at 21:28 at a range of {{convert|10000|m|yd|abbr=on}}; she scored one hit on Princess Royal at 21:32 and straddled Indomitable several times, surrounding her with a salvo of shells, before ceasing fire at 21:35.{{sfn|Campbell 1998|p=254}}

At about 00:30, the leading units of the German line encountered British destroyers and cruisers. A violent firefight at close range ensued; the leading German battleships, including {{lang|de|Posen}}, opened fire on several British warships. In the confusion, the light cruiser {{SMS|Elbing||2}} passed through the German line directly in front of {{lang|de|Posen}} and was rammed. {{lang|de|Posen}} was undamaged, but both of {{lang|de|Elbing}}{{'}}s engine rooms were flooded and the ship came to a halt.{{sfn|Campbell 1998|p=286}} Two and a half hours later, {{lang|de|Elbing}} spotted several approaching British destroyers, and her captain gave the order to scuttle the ship.{{sfn|Campbell 1998|p=295}}

Shortly before 01:00, the German line engaged a flotilla of British destroyers. {{lang|de|Posen}} spotted the destroyers {{HMS|Fortune|1913|2}}, {{HMS|Porpoise|1913|2}}, and {{HMS|Garland|1913|2}} at very close range; she opened fire on the first two ships at ranges between {{convert|800|and|1600|m|yd|abbr=on}}, seriously damaging Porpoise. Fortune quickly sank under fire from {{lang|de|Posen}} and several other battleships, but not before firing two torpedoes which {{lang|de|Posen}} had to evade.{{sfn|Campbell 1998|p=289}} At 01:25, {{lang|de|Westfalen}} illuminated the destroyer {{HMS|Ardent|1913|2}} and opened fire; {{lang|de|Posen}} joined her shortly thereafter and reported several hits at ranges of {{convert|1000|to|1200|m|yd|abbr=on}}.{{sfn|Campbell 1998|p=290}}

Despite the ferocity of the night fighting, the High Seas Fleet punched through the British destroyer forces and reached Horns Reef by 04:00 on 1 June.{{sfn|Tarrant|pp=246–247}} The German fleet reached Wilhelmshaven a few hours later, where {{lang|de|Posen}} and several other battleships from I Battle Squadron took up defensive positions in the outer roadstead.{{sfn|Tarrant|p=263}} Over the course of the battle, the ship had fired fifty-three 28 cm shells, sixty-four 15 cm rounds, and thirty-two 8.8 cm shells.{{sfn|Tarrant|p=292}} The ship and her crew emerged from the battle completely unscathed by enemy fire.{{sfn|Staff Vol. 1|p=33}}

Another fleet advance followed on 18–22 August, during which the I Scouting Group battlecruisers were to bombard the coastal town of Sunderland in an attempt to draw out and destroy Beatty's battlecruisers. As only two of the four German battlecruisers were still in fighting condition, three dreadnoughts were assigned to the Scouting Group for the operation: {{SMS|Markgraf||2}}, {{SMS|Grosser Kurfürst|1913|2}}, and the newly commissioned {{SMS|Bayern||2}}. The High Seas Fleet, including {{lang|de|Posen}},{{sfn|Staff Vol. 1|p=24}} would trail behind and provide cover.{{sfn|Massie|p=682}} At 06:00 on 19 August, {{lang|de|Westfalen}} was torpedoed by the British submarine {{HMS|E23}} {{convert|55|nmi}} north of Terschelling; the ship remained afloat and was detached to return to port.{{sfn|Staff Vol. 1|p=26}} The British were aware of the German plans and sortied the Grand Fleet to meet them. By 14:35, Admiral Scheer had been warned of the Grand Fleet's approach and, unwilling to engage the whole of the Grand Fleet just 11 weeks after the close call at Jutland, turned his forces around and retreated to German ports.{{sfn|Massie|p=683}}

The fleet advanced as far as the Dogger Bank on 19–20 October.{{sfn|Staff Vol. 1|pp=26–27}} The operation led to a brief action on 19 October, during which a British submarine torpedoed the cruiser {{SMS|München||2}}. The failure of the operation (coupled with the action of 19 August) convinced the German naval command to abandon its aggressive fleet strategy in favor of a resumption of the unrestricted submarine warfare campaign.{{sfn|Massie|p=684}} Beginning in June 1917, Wilhelm von Krosigk served as the ship's commanding officer; he held this position until the end of the war in November 1918. {{lang|de|Posen}} sortied to assist the German forces engaged in the Second Battle of Helgoland Bight on 18 November 1917, but did not reach the area until the battle had ended.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|pp=239, 241}}

File:SMS Nassau illustration.jpg

In February 1918, the German navy decided to send an expedition to Finland to support German army units to be deployed there. The Finns were engaged in a civil war; the White Finns sought a conservative government free from the influence of the newly created Soviet Union, while the Red Guards preferred Soviet-style communism. On 23 February, two of {{lang|de|Posen}}{{'}}s sister ships—{{lang|de|Westfalen}} and {{lang|de|Rheinland}}—were assigned as the core of the {{lang|de|Sonderverband Ostsee}} (Special Unit Baltic Sea), under the command of {{lang|de|Konteradmiral}} Hugo Meurer.{{sfn|Ganz|pp=85–86}} The two ships embarked the 14th {{lang|de|Jäger}} Battalion. They departed for Åland on the following morning. Åland was to be a forward operating base, from which the port of Hanko would be secured. From Hanko, the German expedition would assault the capital of Helsingfors. The task force reached the Åland Islands on 5 March, where they encountered the Swedish coastal defense ships {{HSwMS|Sverige}}, {{HSwMS|Thor|1898|2}}, and {{HSwMS|Oscar II||2}}. Negotiations ensued, which resulted in the landing of the German troops on Åland on 7 March; {{lang|de|Westfalen}} then returned to Danzig, where {{lang|de|Posen}} was stationed.{{sfn|Staff Vol. 1|p=27}}

By that time, the {{lang|de|Sonderverband}} had been reinforced by the coastal defense ship {{SMS|Beowulf||2}}, the light cruiser {{SMS|Kolberg||2}}, and several more auxiliaries. Not long before, Germany and Russia had signed the Treaty of Brest-Litovsk, ending the fighting between the two countries. {{lang|de|Posen}} remained in Danzig until 31 March, when she departed for Finland with {{lang|de|Westfalen}}; the ships arrived at Russarö, which was the outer defense for Hanko, by 3 April. The fortress at Russarö was still under Russian control, and the garrison declared their neutrality, which allowed the Germans to go ashore without fighting. The German army quickly took the port, and the British submarines that had been based there were all scuttled by their crews. On 5 April, Meuer secured an agreement with the local Russian naval commander that his ships would not interfere in the German operations.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 8|p=77}}

Helsingfors was the next major objective; Posen had sailed south to Reval to make preparations for the attack on the Finnish capital. The ship got underway on 11 April, and the following day, she and Westfalen passed the fortifications guarding Helsingfors, and they were soon joined by Beowulf. The German ships sent men ashore to take control of the harbor and the Skatudden district, while the Baltic Division attacked the city from the land side. Posen and the other ships provided fire support while the German and White forces fought their way across the city. Four men from the {{lang|de|Posen}}{{'}}s landing party were killed in the fighting and another twelve were wounded, but by 14 April, the Germans and White forces had taken control of Helsingfors. From 18 to 20 April, Posen was sent to try to free Rheinland after the latter vessel had run aground. Two days later, {{lang|de|Posen}} struck a sunken wreck in Helsingfors harbor, which caused minor damage. Posen remained in Helsingfors until 30 April, by which time the White government had been installed firmly in power. Upon leaving the city, Meuer handed control of the harbor facilities over to the White government. On 30 April the ship was detached from the {{lang|de|Sonderverband Ostsee}}. Posen returned to Germany, reaching Kiel by 3 May, where she entered drydock. Repair work lasted until 5 May.{{sfn|Staff Vol. 1|pp=27, 33}}{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 8|pp=77–78}}

On 11 August 1918, {{lang|de|Posen}}, {{lang|de|Westfalen}}, {{SMS|Kaiser|1911|2}}, and {{SMS|Kaiserin||2}} sortied from Wilhelmshaven to support torpedo boats on patrol off Terschelling.{{sfn|Staff Vol. 1|p=27}} On 2 October, {{lang|de|Posen}} moved out into the outer roadsteads of the Jade to provide cover for the returning U-boats of the Flanders Flotilla. {{lang|de|Posen}} was to have taken part in the last fleet operation of the war,{{sfn|Staff Vol. 1|p=33}} planned for 30 October. The operation, scheduled just days before the armistice, envisioned the bulk of the High Seas Fleet sortieing from their base in Wilhelmshaven to engage the British Grand Fleet. In order to retain a better bargaining position for Germany, Admirals Hipper and Scheer intended to inflict as much damage as possible on the British navy, whatever the cost to the fleet.{{sfn|Tarrant|pp=280–281}} Consequently, on 29 October 1918, the order was given to depart from Wilhelmshaven to consolidate the fleet in the Jade roadstead, with the intention of departing the following morning. However, starting on the night of 29 October, sailors on {{SMS|Thüringen||2}} mutinied.{{sfn|Tarrant|pp=281–282}} The unrest spread to other battleships, which forced Hipper and Scheer to cancel the operation and order the battleships dispersed in an attempt to suppress the mutiny.{{sfn|Tarrant|p=282}} {{lang|de|Posen}} and the other ships of I Battle Squadron were sent out into the roadstead on 3 November, then returned to Wilhelmshaven on 6 November.{{sfn|Staff Vol. 1|p=33}} On 9 November, Posen sailed from Brunsbüttel to Wilhelmshaven, arriving there the following day.{{sfn|Hildebrand, Röhr, & Steinmetz Vol. 6|p=242}}

On 11 November 1918, the armistice took effect; according to its terms, eleven battleships and five battlecruisers were to be interned in Scapa Flow for the duration of negotiations for the peace treaty.{{sfn|Campbell & Sieche|p=139}} {{lang|de|Posen}} was not among the ships interned, and she was instead decommissioned on 16 December.{{sfn|Staff Vol. 1|p=33}} They had their guns disabled, along with the four Helgoland-class battleships. Under the terms of the Treaty of Versailles that formally ended the war in June 1919, Posen and the other dreadnoughts that had remained in Germany were to be surrendered to the Allies under Article 185. Negotiations between the Allies over which country received what vessels, and what those ships could be used for began in November. On 5 November, {{lang|de|Posen}} was stricken from the German navy list in preparation to be handed over. While final decisions were still being made, the Allies decided that the ships in question were to sail to either a British or French port, and accordingly, on 8 May 1920, Posen, {{SMS|Oldenburg||2}}, and the torpedo boat {{SMS|V71||2}} sailed for Rosyth, Britain, arriving on 12 May.{{sfn|Dodson & Cant|pp=14, 32–35, 39–45}}{{sfn|Staff Vol. 1|p=33}} On 1 November 1920, she was driven ashore at Hawkcraig, Fife, Scotland.{{Cite newspaper The Times |title=Casualty reports |date=2 November 1920 |page=18 |issue=42557 |column=D }}

The ship was still in British hands by mid-1921, though she was due to be completely scrapped by November that year. The timeline was impossible for any shipyard to keep, and so the government was forced to seek an exception from the other Allied powers to extend the deadline. The government initially sold the ship to Thos. W. Ward on 27 July, but the transaction was cancelled and she was resold to a Dutch firm on 31 August. Posen was taken to Rotterdam, the Netherlands, on 8 October, before being scrapped in Dordrecht the following year.{{sfn|Dodson & Cant|pp=55, 104}}

{{notelist

| notes =

}}

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{{Nassau class battleship}}

{{DEFAULTSORT:Posen}}

Category:Nassau-class battleships

Category:Ships built in Kiel

Category:1908 ships

Category:World War I battleships of Germany

Category:Maritime incidents in 1920

Category:Shipwrecks of Scotland