Babrak Karmal befriended fellow inmate Mir Akbar Khyber, who introduced Karmal to Marxism. Karmal changed his name from Sultan Hussein to Babrak Karmal, which means "Comrade of the Workers'" in Pashtun, to disassociate himself from his bourgeois background. When he was released from prison, he continued his activities in the student union, and began to promote Marxism. Karmal spent the rest of the 1950s and the early 1960s becoming involved with Marxist organizations, of which there were at least four in Afghanistan at the time; two of the four were established by Karmal. When the 1964 Afghan Provisional Constitution, which legalised the
Babrak Karmal put under government surveillance. To mitigate Daoud's suddenly anti-communist directives, the Soviet Union reestablished the PDPA; Taraki was elected its General Secretary and Karmal, Second Secretary. While the Saur Revolution (literally the April Revolution) was planned for August, the assassination of Khyber led to a chain of events which ended with the communists seizing power. Karmal, when taking power in 1979, accused Amin of ordering the assassination of Khyber. Taraki was appointed Chairman of the Presidium of the Revolutionary Council and Chairman of the Council of Ministers, retaining his post as PDPA general secretary. Taraki initially formed a government which