With the abdication of Tsar Nicholas in February 1917 (Old Style), the government of Russia was initially taken over by a Provisional Government established by the Fourth Duma. Alexander Kerensky, who became the most prominent leader of this government, unilaterally abolished the Russian monarchy on 1917, thereby formally abrogating the 1906 Constitution. In November Russia was taken over by the Bolshevik party, leading ultimately to the establishment of the Union of Soviet Socialist Republics on 30 December 1922. Prior to that time, the Communists had enacted a new constitution, firmly establishing Russia as a Bolshevik state. This was in turn superseded by the 1924 Soviet Constitution and the constitutions of 1937 and 1978, the last of which lasted until the fall of the Soviet Union and the adoption of Russia's current governing document in 1993, under which the nation is currently governed.