In April 1809, Russian troops entered the capital of Finland—Abo.
In March 1809, the Russian army under the command of P. I. Bagration and M. B. Barclay de Tolly crossed over the ice of the Gulf of Bothnia into Swedish territory. The Swedish King Gustav IV Adolf was deposed, and his uncle Charles XIII was proclaimed king.
In August 1809, the Treaty of Fredrikshamn was signed, under which Finland and the Aland Islands were ceded to Russia. Sweden undertook to join the Continental Blockade. Soon Alexander I convened a diet of deputies from the Finnish estates in the city of Borgo, where he declared his intention to observe all local laws and privileges of the Finnish population. These provinces formed the Grand Duchy of Finland with the rights of broad political autonomy. It was governed under its own laws, and the staff of the administration was recruited exclusively from local residents. Alexander I adopted the title of Grand Duke of Finland, appointing a governor-general there as a representative of imperial authority. The duchy had its own customs service; its revenues were used only for internal needs and were not merged into the all-Russian budget.