in april 1978 the maos khalq faction led a successful coup that ended in the signing of a 20year treaty of friendship between the two countries. the new government sought to impose a radical series of economic and social reforms on the afghan people. the government ignored soviet recommendations to slow stepped up its shipment of military equipment and sent in combat personnel .in September 1979 a rival maoist faction seized power. it too refused to heed Moscow's advice and followed an even more radical reform program. once again the soviet union increased its military presence in Afghanistan. in December,confronted with an increasingly chaotic situation and the pending triumph of Islamic rebel forces, Russia sent an invasion force of more than 50000 soldiers into Afghanistan and brought babrak karmal, head of the pro-soviet parcham faction,back from exile to serve as the new president.