Leon Trotsky (1879-1940) was a Bolshevik revolutionary and Marxist theorist. He was one of the leaders of the Russian October Revolution, second only to Vladimir Lenin. During the early days of the Soviet Union, he served first as People's Commissar for Foreign Affairs and later as the founder and commander of the Red Army and People's Commissar of War. He was also among the first members of the Politburo. Why fascism was able to conquer only in those countries where social democratic or Stalinist parties blocked the workers and their allies from utilizing a revolutionary situation to remove the capitalists from power. There is a scientific analysis of fascism. It was made by the exiled Bolshevik revolutionary Leon Trotsky not as a postmortem, but during the rise of fascism. This was — along with his analysis of the nature of Stalinism — Trotsky's greatest contribution to Marxist theory. He began the task after Mussolini's victory in Italy in 1922 and brought itto ahigh pointin the years preceding Hitler'striumphin Germany in 1933.