芬蘭大公
During the Finnish War between Sweden and Russia, the four Estates of occupied Finland (Nobility, Clergy, Bourgeoisie and Peasants) were assembled at Porvoo (Borgå) by Tsar Alexander I, the new Grand Duke of Finland, between 25 March and 19 July 1809. The central event at Porvoo was the taking of the sovereign pledge and the oaths of the Estates in Porvoo Cathedral on 29 March. Each of the Estates swore an oath of allegiance, committing themselves to accepting the Emperor as Grand Duke of Finland, and to keeping the constitution and the form of government unchanged. Alexander I subsequently promised to govern Finland in accordance with its laws. This was thought to mean that the emperor confirmed the Swedish Instrument of Government of 1772 as the constitution of Finland, although it was also interpreted to mean that all existing codes and statutes were to be respected. The Diet required that it be convened again after the Finnish War, which separated Finland from Sweden, was concluded. On 17 September that year, the conflict was settled by the Treaty of Fredrikshamn, but it was another 54 years before the Finnish Estates were called to assemble again.