In 1978 the People’s Democratic Party of Afghanistan led the Saur Revolution against President Daoud Khan, who had begun a crackdown against their growing political influence. The new Communist government, led by Hafizullah Amin, was widely unpopular and quickly garnered armed opposition from Mujahideen (fighters engaged in a jihad) who vehemently resisted the Communist regime changes on religious grounds. The Soviet Union became doubtful of President Amin’s loyalty to their cause and, after airlifting over 24,000 troops into Kabul on 24 December 1979, had him assassinated on 27 December, installing Babrak Karmal in his place. Upon the assassination, further troops were airlifted to Kabul and ground units entered Afghanistan via Termez and Kushka. In total some 80,000 Soviet troops entered Afghanistan during the initial invasion and quickly gained control of the cities. The Mujahideen remained in firm control of the countryside and their guerrilla tactics proved highly effective against the conventional Soviet army. By 1982 over 4 million Afghans had fled the conflict as refugees.