Kolchak, Aleksandr Vasilyevich (əlyĭksänˈdər vəsēˈlyəvĭch kəlchäkˈ) [key], 1874–1920, Russian admiral, leader of the anti-Bolshevik forces in W Siberia during the civil war (1918–20). He distinguished himself in the Russo-Japanese War, and in World War I he commanded the Black Sea fleet. After the October Revolution of 1917, Kolchak became (Oct., 1918) minister of war in an anti-Bolshevik government set up in Omsk, Siberia. In November he carried out a coup against the Socialist Revolutionaries in the government and assumed dictatorship over Siberia. At first successful against the Bolshevik forces, he was recognized by the Allies as well as by General Denikin as representing the provisional Russian government. However, his great offensive of 1919 (in which he intended to join the British forces and the Russian counterrevolutionaries on the coast of the White Sea) collapsed rapidly and exposed Denikin's army in S Russia. Kolchak retreated to Irkutsk, lost most of his following (especially the Czechs, who controlled the Trans-Siberian RR) and was betrayed to the Bolsheviks, who shot him and took possession of all of Siberia.