The major event in 1917 that changed the course of Russian history was the Russian Revolution. This revolution had two significant phases: the February Revolution, which led to the abdication of Tsar Nicholas II, and the October Revolution, wherein the Bolsheviks, led by Lenin, seized power. The upheaval ended centuries of imperial rule and ushered in a communist government, altering the political, social, and economic landscape of Russia. The revolution had a profound impact not only on Russia but also on global geopolitics, inspiring communist movements worldwide and leading to the establishment of the Soviet Union.