Soviet leaders sent troops into Afghanistan in December 1979 to support a friendly Marxist-Leninist regime in its conflict against a popular insurgency and help it build a new society. When the Soviet troops withdrew nine years later, they left behind a state that had none of the nominal characteristics of a Soviet-type Communist country. During the war, the People's Democratic Party of Afghanistan had discarded Marxism-Leninism and turned to Islam. This article examines how, with Moscow's support, the Afghan Communists Islamicized their discourse and policies as they tried to gain support from the population and co-opt insurgent fighters.