Finnish War: Sweden loses the fortress of Sveaborg to Russia.

The Finnish War was fought between the Kingdom of Sweden and the Russian Empire from 21 February 1808 to 17 September 1809 as part of the Napoleonic Wars. 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.

Suomenlinna, or Sveaborg, is a sea fortress composed of eight islands, of which six have been fortified. Located about 4 km southeast of the city center of Helsinki, the capital of Finland, Suomenlinna is a popular destination for both tourists and locals, who enjoy it as a picturesque picnic site.