The Soviet Union intervened in Afghanistan in late 1979 to support the communist government against anti-communist Muslim guerrillas during the Afghan civil war from 1978-1992. The Soviets controlled urban areas but could not take the mountainous regions where rebels received support from the US, China, Saudi Arabia and used missiles to counter Soviet air power. The costly war drained Soviet resources and contributed to weaknesses that led to the dissolution of the Soviet Union in 1991. Over 50,000 Soviet troops were killed or wounded in the conflict.