Battle of Grengam The Battle of Grengam ( , . ) of 1720 was the last major naval battle in the Great Northern War that took place in the Åland Islands , in the Ledsund strait between the island communities of Föglö and Lemland . The battle marked the end of Russia n and Swedish offensive naval operations in Baltic waters . The Russian fleet conducted one more raid on the Swedish coast in spring 1721 , whereupon the Treaty of Nystad was signed , ending the war . Location of the battle . The main shipping route between the ports of Stockholm in Sweden and Turku in Finland passes through the Åland Islands . It enters the Ledsund strait from south - west with Föglö on the south - east side and Lemland on the north - west . An anchorage ( ) of the shore of Flisö in Föglö is protected from the prevailing south - westerly winds by two small islands . This anchorage was previously called " Granhamn " , Swedish for ' Spruce harbor ' . On modern maps it is marked as " Rödskärs flädan " after the larger of the two protecting islands . The smaller island is now called " Granhamns holmen " or Granhamn ' s island . It should not be confused with the island also named " Granhamn " in the Stockholm archipelago . Name . The word " Grengam " in the name of the battle is a romanization of Гренгам , which is the traditional Russian cyrillization of " Gränhamn " , an older spelling of " Granhamn " . The spelling " Gränhamn " was used on Hans Hansson ' s map of Åland from about 1650 . In Sweden the battle is known as the " Battle of Ledsund " after the Ledsund strait . In Finland the name " Battle of Flisö " ( ) is used . The battle . The Swedish and Russian accounts of the battle differ significantly . Both sides agree that on July 27 , 1720 , a group of Swedish ships under Vice Admiral Carl Georg Siöblad attacked the Russian fleet and , in a pitched battle , had their four frigates captured by Russian sailors . Russian accounts . The Swedish squadron consisting of a 52 - gun ship of the line , four frigates and nine smaller craft with a total of 156 guns and over 1 , 000 marines , made an attempt to attack the moving Russian fleet . General Mikhail Golitsyn managed to take an advantageous position in the narrow and shallow strait of Flisesund and ordered his ships into a semicircle formation . The Swedish ship of the line and four frigates entered the strait in pursuit of the Russian ships . Two frigates ran aground , making maneuvering for the rest of the squadron difficult . In the fierce battle that followed , all four Swedish frigates were boarded . The only ship that managed to escape was Siöblad ’ s flagship . Swedish accounts . A small Swedish naval unit sailed right into the mighty Russian fleet anchored at Granhamn . A fierce battle took place , the Swedes lost their four frigates after they had run aground but the Russian losses became so heavy that the entire fleet quickly decided to withdraw from Åland , leaving 43 sunken ships and 1000 dead Russians behind . The Russian losses prevented their navy from launching any further major operations until the war ended with the Treaty of Nystad the following year . Aftermath . Both sides claim the outcome of the battle as their own victory . They agree only in that four Swedish frigates , the 34 - gun frigate " Stor Phoenix " , the 30 - gun " Vainqueur " , the 22 - gun " Kiskin " and the 18 - gun " Danska Örn " were captured by the Russians . No significant naval battles took place between the Russian and Swedish navies after this one until Sweden ' s defeat in the war was sealed by the Treaty of Nystad . Russian accounts . The Swedes lost 103 killed and 407 captured . The Russians had 82 killed and 236 wounded . The Battle of Grengam demonstrated the skillful use of the rowing fleet in the skerries environment and efficient reconnaissance and selection of the combat site , as well as perfect timing for the attack from different directions . The victory at Grengam allowed the Russians to consolidate in the archipelago , which was very important for carrying out operations against Swedish shipping in the area . Swedish accounts . Four Swedish frigates ran aground and were captured by the Russian Navy . 43 out of 61 Russian galleys , were either sunk by the Swedish force or burnt and abandoned after the battle . The Swedish Vice Admiral Carl Georg Siöblad was initially criticised after the battle , but when the scope of the Russian losses were discovered he was praised . Russia celebrated the battle as a victory , but their fleet was unable to launch effective operations until the end of the war in 1721 . Commemoration . Like the previous Battle of Gangut , the Battle of Grengam was fought on Saint Pantaleon Day . In order to commemorate the perceived victory , a timber church to this saint was built in Saint Petersburg in 1722 . It was rebuilt in stone in 1735 - 39 . Since 1914 the facade of the church has borne two marble plaques listing the ships and regiments that fought at Gangut and Grengam .