Lake Ladoga Stolbovo, the northern and western coast was ceded by Russia to Sweden. In 1721, after the Great Northern War, it was restitution to Russia by the Treaty of Nystad. Later, in 1812–1940 the lake was shared between Finland and Russia. According to the conditions of the 1920 Tartu Peace Treaty militarization of the lake was severely restricted. However, both Soviet Russia and Finland had flotillas in Ladoga (see also Finnish Ladoga Naval Detachment). After the Winter War (1939–40) according to the Moscow Peace Treaty, Ladoga, previously shared with Finland, became an internal basin of the Soviet Union. During the Continuation
Finnish Ladoga Naval Detachment Finns had intended to mount further landing operations to secure the island of Valamo but Soviets withdrew from there as well as from most of the other island on the lake voluntarily. Finnish forces took control of the island of Valamo on 20 September and island of Konevitsa on 25 September. Since Soviet forces remained inactive on lake Ladoga for the rest of the 1941 Finnish naval forces concentrated on security and transport duties. After Finns had captured maps of the Soviet naval minefields on the lake several boats were detailed for minesweeping duties which however yielded no results nor