A combination of economic breakdown, war-weariness, and discontent with the autocratic system of government triggered the Russian Revolution in 1917. The overthrow of the monarchy initially brought into office a coalition of liberals and moderate socialists, but their failed policies led to seizure of power by the communist Bolsheviks on 25 October 1917 (7 November New Style). In 1922, Soviet Russia, along with Soviet Ukraine, Soviet Belarus, and the Transcaucasian SFSR signed the Treaty on the Creation of the USSR, officially merging all four republics to form the Soviet Union as a country. Between 1922 and 1991 the history of Russia became essentially the history of the Soviet Union, effectively an ideologically-based state roughly conterminous with the Russian Empire before the 1918 Treaty of Brest-Litovsk. From its first years, government in the Soviet Union based itself on the one-party rule of the Communists, as the Bolsheviks called themselves, beginning in March 1918. The approach to the building of socialism, however, varied over different periods in Soviet history: from the mixed economy and diverse society and culture of the 1920s through the command economy and repressions of the Joseph Stalin era to the "era of stagnation" from the 1960s to the 1980s. During this period, the Soviet Union was one of the victors in World War II after recovering from a massive surprise invasion in 1941 by its previously secretly cooperative partner, Nazi Germany. It became a superpower competing with fellow new superpower the United States and other Western countries in the Cold War. The USSR was successful with its space program, launching the first artificial satellite and first man into space.