Battle of Frisches Haff The battle of Frisches Haff or battle of Neuwarp was a naval battle between Sweden and Prussia that took place 10 September 1759 as part of the ongoing Seven Years ' War . The battle took place in the Oder Lagoon ( ) between Neuwarp and Usedom , and is named after an ambiguous earlier name for the Lagoon , " Frisches Haff " , which later exclusively denoted the Vistula Lagoon . Swedish naval forces consisting of 28 vessels and 2 , 250 men under Captain Lieutenant Carl Rutensparre and Wilhelm von Carpelan destroyed a Prussian force of 13 vessels and 700 men under captain von Köller . The consequence of the battle was that the small fleet Prussia had at its disposal ceased to exist . The loss of naval supremacy meant also that the Prussian positions at Usedom and Wollin became untenable and were occupied by Swedish troops . Swedish intervention in the Seven Years ' War . At the outbreak of the conflict , Sweden was led by a government dominated by the pro - French " Caps " party , which felt that this war ( mainly aimed against Prussia ) was the chance for Sweden to recapture territories lost to Prussia in the past in Pomerania and restore the mouth of the Oder to Swedish control . The chancellor and head of the " Caps " party , baron Anders Johan von Höpken , sent an army of 14 , 500 men to Stralsund , capital of Swedish Pomerania , under field - marshal Ungern - Sternberg , with his main mission being the capture of Stettin ( today in Poland ) , which controls the mouths of the Oder . First operations . The Swedes launched a first offensive but were beaten back in Stralsund by the Prussian army under marshal Lehwaldt . Ungern - Sternberg was replaced by count von Rosen , who took no risks and left himself blockaded in Stralsund . However , a Russian offensive in west Prussia forced Lehwaldt to leave Swedish Pomerania on 27 June 1758 . Sweden sent reinforcements and a new commander - in - chief , count Hamilton , who profited from Prussian difficulties by going back on the offensive . Although Prussian troops in the area had been heavily denuded to face the Russian threat , they put up a tenacious resistance to the Swedes and battles and skirmishes came one after the other without either of the belligerents able to gain a decisive advantage over the other . The conflict took a naval turn when the Prussians built a fleet at Stettin , by the more or less fortunate transformation of fishing or transport boats into warships , to defy a Swedish squadron supporting their land offensive . Informed of these preparations , the Swedes decided to destroy this fleet . Course . At the start of August 1759 , the Swedish squadron under Ruthensparre moved into the Oder , moving towards the Stettin lagoon . On 8 August it forced the defences of Peenemünde and penetrated the western half of the lagoon ( called " Kleines Haff " , or Little Lagoon , by the Germans ) . On 22 August the Swedes won an initial engagement against a fleet under captain von Köller off Anclam . On 10 September , the two fleets again faced each other , near Neuwarp . The Swedish ships commanded by Wilhelm von Carpellan were ranged in 4 lines - in the first were the most powerful ships ( four 13 - gun galleys armed ) , then four 5 - gun demi - galleys ( with mixed sail and oar propulsion ) , then 3 sloop s and 1 ship with howitzer s , and finally a line of 13 gunboat s . For their part , the Prussians had four galiot s and four galleys with 12 cannon each as well as 5 canonnières . Once within range , the Swedes placed themselves in a single line . However , the three Swedish demi - galleys and 9 gunboats sailed towards the south where unidentified sailing vessels had appeared - these turned out to be neutral ships , but this meant these Swedish ships did not take part in the start of the four - hour battle . The battle ended in a heavy Prussian defeat , with their main ships sunk or captured and more than 600 of their sailors captured , for smaller losses ( 13 killed and 14 wounded ) on the Swedish side . Results . The victory guaranteed Swedish control of the lagoon , which they exploited by capturing the island of Wollin . However , their ultimate goal of Stettin remained in Prussian hands . Undaunted , the Prussians began to build a new fleet . The Battle of Frisches Haff was thus a short - lived victory for the Swedes and the Russian retreat from the war of 1762 placed them in a very difficult situation . Realising they did not have a large enough force to hold off the redoubtable troops under king Frederick II of Prussia on their own , the Swedes proposed a peace settlement to him based on a return to the pre - war " status quo " . Frederick accepted the proposal and formalised it by signing the treaty of Hamburg on 22 May 1762 .