Without a previous declaration of war, Russian troops cross the border to Sweden at Abborfors in eastern Finland, thus beginning the Finnish War, in which Sweden will lose the eastern half of the country (i.e. Finland) to Russia.
The Finnish War (Swedish: Finska kriget, Russian: Финляндская война, Finnish: Suomen sota) was fought between the Kingdom of Sweden and the Russian Empire from 21 February 1808 to 17 September 1809. As a result of the war, the eastern third of Sweden was established as the autonomous Grand Duchy of Finland within the Russian Empire. Other notable effects were the Swedish parliament's adoption of a new constitution and the establishment of the House of Bernadotte, the new Swedish royal house, in 1818.