Short answers, pulled from the story.
Leon Trotsky, born Lev Davidovich Bronstein, was a Russian revolutionary, Soviet politician, and political theorist. He was a key figure in the 1905 Revolution, the October Revolution of 1917, the Russian Civil War, and the founding of the Soviet Union. He and Vladimir Lenin were widely considered the two most prominent figures in the Soviet state from 1917 until Lenin's death in 1924.
Leon Trotsky was assassinated in 1940 in Mexico City by Ramon Mercader, a Stalinist agent. He had already been sentenced to death in absentia at the Moscow show trials in 1936.
Leon Trotsky was outmanoeuvred by Joseph Stalin after Lenin's death and led the Left Opposition against the growing Soviet bureaucracy. He was expelled from the Politburo in 1926, expelled from the party in 1927, exiled to Alma Ata in 1928, and deported from the Soviet Union to Turkey in 1929.
Leon Trotsky served as People's Commissar of Army and Navy Affairs from 1918, building the Red Army and leading it to victory in the Russian Civil War. He increased the Red Army from under 300,000 in May 1918 to one million by October and introduced political commissars to ensure loyalty among former imperial officers.
Leon Trotsky's theory of permanent revolution held that the revolution could survive only if it spread to more advanced capitalist countries. This put him at odds with Stalin's theory of socialism in one country, and he defended proletarian internationalism in exile.
In The Revolution Betrayed, published in 1936, Leon Trotsky argued that the Soviet Union had become a degenerated workers' state. In 1938 he founded the Fourth International as an alternative to the Comintern.
Leon Trotsky was born on the 7th of November 1879 in Yanovka, a village then in the Kherson Governorate of the Russian Empire and now in the Kirovohrad Oblast of Ukraine. He was born into a wealthy but illiterate Jewish farming family under the name Lev Davidovich Bronstein.