Finland had declared independence from what was the Russian Empire, at that time embroiled in the Russian Civil War, on 6 December 1917. At the time of the declaration of independence, monarchists were a minority in the Finnish Parliament, and Finland was declared a republic. A civil war followed, and afterwards, while the pro-republic Social Democratic Party was excluded from the Parliament and before a new constitution was adopted, Frederick was elected to the throne of Finland on 9 October 1918.
Lithuania had already taken a similar step in July 1918, electing Wilhelm Karl, Duke of Urach and Count of Württemberg, as King Mindaugas II of Lithuania. In Latvia and Estonia, a "General Provincial Assembly" consisting of Baltic-German aristocrats had called upon the German Emperor, Wilhelm II, to recognize the Baltic provinces as a joint monarchy and a German protectorate. Adolf Friedrich, Duke of Mecklenburg-Schwerin, was nominated Duke of "the United Baltic Duchy" by the Germans.
At independence, Finland had, like the Baltic provinces, close ties with the German Empire. Germany was the only international power that had supported the preparations for independence, not least by training volunteers as Finnish Jäger troops. Germany had also intervened in the Finnish Civil War, despite its own precarious situation. Finland's position vis-a-vis Germany was already evolving towards that of a protectorate by Spring 1918, and the election of Prince Frederick, brother-in-law of Wilhelm II, was viewed as a confirmation of the close relations between the two nations. The strongly pro-German prime minister, Juho Kusti Paasikivi, and his government offered the crown to Prince Frederick in October 1918.
The adoption of a new monarchist constitution had been delayed because it did not get the required qualified majority (the legitimacy of the royal election was based upon the Instrument of Government of 1772, adopted under King Gustav III of Sweden, when Finland had been a part of the Kingdom of Sweden. The same constitutional document had also served as the basis for the rule of the Russian Emperors, as Grand Dukes of Finland, during the 19th century.
A member of the Finnish Parliament, Gustaf Arokallio, suggested the monarchical designation "Charles I, King of Finland and Karelia, Duke of Åland, Grand Duke of Lapland, Lord of Kaleva and the North" (Finnish: Kaarle I, Suomen ja Karjalan kuningas, Ahvenanmaan herttua, Lapinmaan suuriruhtinas, Kalevan ja Pohjolan isäntä; Swedish: Karl I, Kung av Finland och Karelen, hertig av Åland, storhertig av Lappland, herre över Kaleva och Pohjola).