On Germany's urge Finland had declared itself independent from Russia on December 6, 1917, (recognized by the Soviet Union on January 4th, 1918), and there was a fierce debate on whether the new state should declare itself a republic or remain a monarchy. This culminated after the Civil War in Finland, during the Social Democrats exclusion from the Eduskunta, which on October 9, 1918, elected the German prince Frederick of Hesse to the Finnish throne. (German spelling: Prinz Friedrich Karl von Hessen-Kassel.)
Lithuania had already in July 1918 taken the similar step, electing Wilhelm Karl, Duke of Urach, Count of Württemberg (1864-1928), to King Mindove II of Lithuania. For Latvia and Estonia, a "General Provincial Assembly" in Riga had called upon the German Kaiser Wilhelm to recognize the Baltic provinces as a joint monarchy and a German protectorate. Consequently Adolf Friedrich, Duke of Mecklenburg-Schwerin (1873-1969), brother of Prince Hendrik of the Netherlands, was nominated Duke of "the United Baltic Duchy" by the Germans.
Independent Finland had initially, like the Baltic province, close ties with Imperial Germany. Germany was the only Power who had supported the preparations for the independence, not the least by the training of volountary Finnish Jaeger troops. Germany had also made a military intervention in the Civil War in Finland, despite her own precarious situation. Finland's position vis-à-vis Germany was already in spring 1918 evolving towards that of a protectorate, and the election of Prinz Friedrich, brother-in-law to Emperor Wilhelm II of Germany, was rather thought of as a confirmation of the close relations.
The adoption of a new monarchist constitution had been delayed, and 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 Sweden. The same constitutional document had also served as the basis for the rule of the Russian Tsars, as Grand Dukes of Finland, during the 19th century.
On November 11, 1918, the armistice between the warring fractions of World War I was signed, and two days earlier Kaiser Wilhelm had abdicated and Germany was declared a Republic. Germany's defeat in the war, and the stated fact that none of the allies would ever accept a German-born prince as the king of Finland, led Frederick to finally renounce the throne on December 14, 1918, and subsequently for Finland to also adopt a republican constitution.
See also: List of Finnish rulers