Siege of Stralsund ( 1711 – 15 ) The Siege of Stralsund was a battle during the Great Northern War . The Swedish Empire defended her Swedish Pomeranian port of Stralsund against a coalition of Denmark - Norway , the Electorate of Saxony and the Tsardom of Russia , which was joined by Brandenburg - Prussia during the siege . A first attempt to take Stralsund was made in 1711 , when the allies closed in on the town . Swedish relief forced the coalition to withdraw from the fortifications , whereupon the besieging armies drew a wider ring along the lines of the Recknitz and Peene rivers . Magnus Stenbock ' s victory at Gadebusch for a short time distracted the allies , but after Stenbock ' s pursuit and subsequent defeat , Brandenburg - Prussia as well as Hanover , ruled in personal union with Great Britain , joined the anti - Swedish alliance . The allies agreed that Denmark should cede her claims to Bremen - Verden to Hanover , and in turn Denmark was promised the northern parts of Swedish Pomerania with Stralsund , while the southern parts were to become Prussian . In 1714 , Charles XII of Sweden rode to Stralsund from his Turkish exile to lead the defense in person . From 12 July to 24 December 1715 , the allies sieged the town and eventually forced its surrender . Charles XII escaped to Sweden . Stralsund remained under Danish control until it was returned to Sweden by the Treaty of Frederiksborg . Prelude . In Poltava , the Swedish Empire lost the initiative in the Great Northern War . With Charles XII of Sweden ' s main army destroyed , the anti - Swedish alliance of the Tsardom of Russia , Denmark - Norway and Saxe - Poland - Lithuania re - constituted in the Treaty of Thorn and the Treaty of Copenhagen , the Swedish king exiled to Bender and Sweden ' s provinces of Finland and Livonia invaded , the Swedish defense relied on 11 , 800 soldiers garrisoned in northern Germany , and an army of 10 , 000 men in Greater Poland commanded by Ernst Detlof von Krassow . The latter was in full retreat , harassed by Saxon forces and a plague that had broken out in Poland . The Swedish government issued mobilization orders for Swedish Pomerania on 8 April 1711 . 3 , 800 men aged between twenty and forty years were to be drawn to serve a five years term . Stralsund had recovered from the destruction of 1678 , but in 1711 , the plague carried to Pomerania with the retreating Swedish forces of the Krassow corps caused thousands of deaths . The Swedes were pursued by the armies of the anti - Swedish coalition , who reached and laid siege to Stralsund in 1711 . This pursuit through formerly neutral Reich territory was made possible by the death of emperor Joseph I in April : until Joseph I ' s successor Charles VI was inaugurated , the imperial constitution ruled that August the Strong , one of the constituents of the anti - Swedish coalition , was in charge of northern Germany ' s imperial affairs . Thus , when the Swedish forces withdrew to their fortified strongholds of Stralsund , Stettin ( Szczecin ) and Wismar , 6 , 000 Saxons , 6 , 000 Poles , and 12 , 000 Russians were able to follow up from the southeast . Another 25 , 000 Danes moved into the empire via Holstein - Gottorp , and approached Stralsund from the west . Siege . A Swedish relief force under Magnus Stenbock ' s command with a strength of 6 , 000 to 10 , 000 men landed on Rügen on 25 September 1711 , whereupon the Danish - Saxon - Russian siege army withdrew to the Recknitz and Peene rivers . Instead of a launching another major assault on the town , the allies were content with minor raids and skirmishes into the pocket in the following years . Swedish general Gustav Dücker requested reinforcements , and in May 1712 was supplied with an additional 6 , 391 foot and 4 , 800 horse from Sweden . Also , Dücker concentrated all Swedish forces scattered in Pomeranian garrisons , another 8 , 000 men , in Stralsund , while the allied strength was about 23 , 000 men . At this time , Frederik IV of Denmark - Norway was not interested in annexing Stralsund to his empire . When he re - entered the war in 1709 , Frederik had promised to not attack Swedish territories in the Holy Roman Empire and protect their citizens wherever they pledge loyalty to him . Accordingly , Frederik IV had agreed in a convention of 1711 that Stralsund along with northern Swedish Pomerania should be annexed by August the Strong , elector of Saxony and king of Poland - Lithuania . However , after George I of Brunswick - Lüneburg ( Hanover ) ascended the throne of Great Britain , who had dropped out of the War of Spanish Succession in the Peace of Utrecht in 1713 and was thus free to enter the anti - Swedish alliance in the Great Northern War , Frederik IV changed his mind . Already in 1712 , Denmark and Hanover had invaded and partitioned Bremen - Verden . The Stralsund area had been tied to Denmark in the Late Middle Ages , was of strategic importance as a bridgehead into the Holy Roman Empire , and a potent exporter of wool and grain . First Danish claims to northern Swedish Pomerania were formulated in 1713 , and a respective treaty was drafted in May 1715 between Frederick IV and George I which guaranteed the Danish occupied Swedish dominion of Bremen - Verden to George I in return for him entering the war on Frederik ' s side , and Pomerania north of the Peene river as well as 30 , 000 taler s to Frederik IV . When Brandenburg - Prussia , keen to annex Swedish Pomerania as well , joined the allies in summer , a Dano - Prussian treaty was concluded partitioning Swedish Pomerania along the Peene , with Denmark being assured her claims for the northern part with Stralsund , and Brandenburg - Prussia for the southern part with Stettin . August the Strong ' s protests and Danish tendencies to minimize their military efforts in the coalition after the treaty , resulting from Frederik IV ' s understanding that he now would gain Stralsund anyway , led to quarrels in the siege force . Stenbock ' s forces turned west with 16 , 000 men to face the allies at Gadebusch , leaving 3 , 000 men to garrison Stralsund . Their victory and subsequent westward movement distracted the allies from the siege , yet when Stenbock burned down Danish Altona , Russian forces burned Swedish Pomeranian Wolgast east of Stralsund in revenge in 1713 . The allies were free to concentrate on Stralsund again after Stenbock ' s forces , pursued by 36 , 000 Poles , Russians and Saxons , were defeated in the Battle of Tönning on 16 May 1713 . Before re - joining with the siege army near Stralsund , Russian forces under Alexander Menshikov ' s command and a Saxon engineur corps were deployed from Tönning to Stettin , the second major Swedish fortress in Pomerania , and captured it on 29 September 1713 . However , Russian tsar Peter the Great had to withdraw his forces from the Holy Roman Empire by the terms of the Treaty of Adrianople , concluded on 25 June 1713 as a consequence of the Pruth Campaign . Charles XII of Sweden , exiled to Bender in the Ottoman Empire between the Surrender at Perevolochna and his return in 1714 , had envisioned that Stralsund would constitute the base of a renewed Swedish attack on Peter the Great . Charles XII ' s plans foresaw a two - fold assault of a Swedish army from Pomerania and a Turkish army from the South . When Charles XII reached Stralsund in November 1714 , the town ' s garrison was reinforced to a strength of 17 , 000 men . Searching for allies , Charles XII also negotiated with Brandenburg - Prussia , but was unwilling to meet Frederick William I ' s demands on Stettin and a 400 , 000 reichstaler s payment . In April 1715 , Brandenburg - Prussia declared war . Though George I was not involved in the war as the king of Great Britain , but merely as the duke of Hanover , the Danish navy was assisted in the siege by eight British vessels , detached by British admiral John Norris , who was ordered to guard the Maritime Powers ' merchants in the Baltic Sea . In July , the allied forces closed in on Stralsund from the landside , and in November a combined Danish - Saxon - Prussian army landed at Groß Stresow and took the island of Rügen north of the town . When defeat became inevitable , Charles XII escaped and the defendants surrendered on Christmas Eve . Stralsund became the capitol of Danish Pomerania . Aftermath . After Stralsund ' s surrender , a Danish administration under commander von Stöcken was set up , and 1028 Swedish prisoners of war were detained in the town . Yet , many noble and burgher families - Pomeranian , Swedish or intermarried - remained loyal to Sweden . The Danish government reacted by prohibiting contacts to Sweden and obliging the landowners to pledge allegiance , otherwise , they would be stripped of their lands or expelled . As a consequence , an unknown number emigrated to Sweden , including Swedish prisoners of war who were able to escape with the help of the local population . Of sixty - nine high ranking Swedish officials and officers detained in Stralsund in January 1716 , only thirty - one were still in town in March of the following year . When the local population continued to maintain close contacts with Sweden and aid Swedish refugees , Danish guards started to patrol the coast and investigate the traffic with Sweden , before this traffic was prohibited altogether until 1719 . Since only a few nobles had pledged allegiance to Frederik IV in August 1716 , the Danish government issued a deadline , and in October started to expropriate those who had not given the oath to the Danish king . Also in 1716 , Swedish Wismar surrendered to the allies , eliminating Sweden ' s last stronghold on the southern Baltic coast . By the end of the war however , Stralsund was restored to Sweden . The siege of Stralsund marked the beginning of a friendship between Frederick William I of Prussia and Huguenot refugee Jacques Egide Duhan de Jandun , whom he first met when he was in the service of field marshal Alexander von Dohna in 1715 . In the following year , Frederick William I entrusted Duhan den Jandun with the raising of his then four - year - old son , later known as Frederick the Great .