The August Coup
Aug. 18-22, 1991

Members of the Politburo and the heads of the Soviet military and security services detained Soviet President Gorbachev at his villa in the Crimea. A popular resistance in Moscow under the leadership of Boris Yeltsin and the refusal of army units to stop the uprising led to the collapse of the coup.

The result was the end of the Communist party's dominance, and the beginning of the disintegration of the Soviet Union.

From infoplease :
www link :
August Coup