Finland–Sweden border border continues south into the northern Baltic Sea to a point where it meets the zone border of Estonia. The tripoint between the economic zones is defined by a treaty signed in 2001. The Finnish–Swedish border was created in 1809 by the Treaty of Fredrikshamn, as Sweden ceded Finland over to Russia. The course of the border was described in the fifth article of the treaty, without great detail. The borders were agreed to be the Sea of Åland, the Gulf of Bothnia, and the rivers Tornionjoki and Muonionjoki. Islands in the sea belonged to whichever country was the nearest
Finland–Russia border most of which were Savonians. After the Finnish War, the Treaty of Fredrikshamn converted all of Finland from Swedish territory to a Russian possession, the Grand Duchy of Finland. The Finnish–Russian border was moved back to the pre-1721 location, so that the Grand Duchy gained the so-called "Old Finland", territories previously held by Sweden, in 1812. After Finland became independent in 1917, there was the Finnish Civil War in 1918, and even after this war, the Russian Civil War continued. Finnish activists often crossed the border into Soviet territory in order to fight in the "heimosodat", wars aiming at Finnish