The defeat of the Russian Empire in World War I led to the seizure of power by the Communists and the formation of the USSR. The brutal rule of Josef STALIN (1924-53) strengthened Russian dominance of the Soviet Union at a cost of tens of millions of lives. The Soviet economy and society stagnated in the following decades until General Secretary Mikhail GORBACHEV (1985-91) introduced glasnost (openness) and perestroika (restructuring) in an attempt to modernize Communism. In December 1991 the USSR splintered into 15 independent republics. Russia consists of more than 100 etnical groups, and most of them have their own language.