In December 1979, the USSR invaded Afghanistan with 80,000 soldiers supported by 1,800 tanks. The government of Afghan President Hafizullah Amin was overthrown in less than a week at a minimal cost of only 86 fatalities. However, Marshal Sokolov was unable to establish control outside the major population centers, and despite reinforcements that increased its total occupation force to 100,000 troops, 80 percent of the country remained outside the control of its military or its puppet government. Over the 10 years of the failed occupation, Soviet forces lost an average of 1,445 dead annually (63 percent of which were combat-related), until they finally retreated in a two-stage, largely peaceful withdrawal that was completed in February 1989.