The Russian Revolutionary Leader referred to in the crossword solution is Vladimir Lenin. He was a Marxist revolutionary and political theorist who led the October Revolution of 1917, which overthrew the Tsarist autocracy and established the Soviet Union. He was the first head of the Soviet government and served as the leader of the Communist Party of the Soviet Union from 1912 until his death in 1924. Lenin's ideas, known as Leninism, formed the basis of Marxism-Leninism, a political ideology that would later become the official state ideology of the Soviet Union.