The Finnish War (1808–1809) was a pivotal conflict between Sweden and Russia that dramatically altered Finland's political future. As part of the Napoleonic Wars, Russia invaded Finland, which was then an eastern province of Sweden. The war began after Sweden, under King Gustav IV Adolf, refused to comply with the Treaty of Tilsit and the Continental System, prompting Russia to act to secure its northern borders.
Finland became the primary battleground, with Russian forces quickly advancing through Finnish territory, capturing key locations like Helsinki and Turku. Swedish defenses, led by General Wilhelm Mauritz Klingspor, were poorly prepared, and Russian troops steadily gained control of the region, with Finnish guerrilla resistance offering limited opposition.
By late 1808, all of Finland had fallen under Russian occupation. The war culminated in Sweden's defeat, formalized by the Treaty of Fredrikshamn in September 1809. Sweden ceded all of Finland to Russia, marking the end of over 600 years of Swedish rule in Finland. Finland was reorganized as the autonomous Grand Duchy of Finland under Russian sovereignty, though it retained a degree of self-governance and its own laws.
Finnish War, aftermath. @ Geopsis
This shift fundamentally altered Finland's place in the region, beginning its association with Russia, which would last until 1917. The war also led to significant changes in Sweden, including the adoption of a new constitution and the establishment of the House of Bernadotte. Finland's separation from Sweden is one of the most important events in Finnish history, laying the groundwork for its eventual path toward independence.