Political map of Europe & the Mediterranean 25 December 1991 (Collapse of the Soviet Union): The failure of the August coup (1991 Soviet coup d'etat attempt) broke the Communist Party (Communist Party of the Soviet Union) and ended Soviet dominance. Real power now lay in the hands of the component republics (Republics of the Soviet Union), such as Russia and Ukraine. On December 25, unable to stop the republics from asserting their independence, Gorbachev (Mikhail Gorbachev) resigned and the Soviet Union was officially dissolved (Dissolution of the Soviet Union).