The Bolshevik Revolution
World War I demonstrated czarist corruption and inefficiency, and only patriotism held the poorly equipped army together for a time. Disorders broke out in Petrograd (renamed Leningrad and now St. Petersburg) in March 1917, and defection of the Petrograd garrison launched the revolution. Nicholas II was forced to abdicate on March 15, 1917, and he and his family were killed by revolutionaries on July 16, 1918. A provisional government under the successive prime ministerships of Prince Lvov and a moderate, Alexander Kerensky, lost ground to the radical, or Bolshevik, wing of the Socialist Democratic Labor Party. On Nov. 7, 1917, the Bolshevik Revolution, engineered by Vladimir Lenin and Leon Trotsky, overthrew the Kerensky government, and authority was vested in a Council of People's Commissars, with Lenin as prime minister.
The humiliating Treaty of Brest-Litovsk (March 3, 1918) concluded the war with Germany, but civil war and foreign intervention delayed Communist control of all Russia until 1920. A brief war with Poland in 1920 resulted in Russian defeat.