Finland during the Great Northern War
Finland during the Great Northern War was dominated by the Russian invasion and subsequent military occupation of Finland, then part of the Sweden, from 1714 until the treaty of Nystad 1721, which ended the Great Northern War. The period is also referred to as den stora ofreden ("the great discord") in Swedish or isoviha ("the great wrath") in Finnish.
Background
Finland was left largely to fend for itself after the disaster of Poltava in 1709. Russia captured Viborg (Russian: Выборг (Vyborg), Finnish: Viipuri) in 1710 and already in 1712 started their first campaign to capture Finland which ended in failure. A more organized campaign starting in 1713 managed to capture Helsinki/Helsingfors and drive defending Swedes away from the coast. The Swedish army in Finland was defeated in Storkyro (Isokyrö) in February 1714 where the Russians won a decisive victory. Swedish efforts to hinder the Russian advance by blockading the coastal sea route at Hangö ended in failure in late July in battle of Gangut. The presence of a Russian galley fleet in the Gulf of Bothnia forced, in the end, both the Swedish fleet and army to largely abandon Finland in late 1714. Even the Swedish areas on the western side of the Gulf of Bothnia were ravaged by the Russians. The city of Umeå was burned to the ground by the Russians on 18 September 1714, and after struggling to rebuild was razed again in 1719, 1720, and 1721.