Swedish naval commander responsible for the overwhelming Swedish victory at the Second Battle of Svensksund, one of the largest naval battles in history. He is often better remembered, however, as the commander of the fortress of Sveaborg during the Finnish war of 1808, which was fought between Sweden and Imperial Russia, and ended in Cronstedt surrendering the fortress.
European power politics also determined Sveaborg's fate. In the war of 1808-1809, which was a direct consequence of the treaties between Napoleon and Alexander I, Russia occupied Finland. Sveaborg surrendered and became a Russian garrison for the following 110 years. At the turn of the century there were about 4000 Russian soldiers in Sveaborg. The fortress remained in the state it had been under Swedish rule until the bombings during the Crimean War in 1855, when the British and French Navies ·fired on the fort. In the repairs and modernisation , undertaken after that, some of the damaged buildings were torn down or made lower and a new coastal defence line of earth banks was constructed.
Before the First World War, Sveaborg, mainly serving as a depot area, formed part of the defence scheme, "Peter the Great's Sea Fortress". The intention was that Sveaborg, together with Tallinn, would block off the entire Gulf of Finland and guarantee the security of St Petersburg, the Capital of Russia.