Complex sentence: 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.
Split into simpler sentences: Karmal spent the rest of the 1950s and the early 1960s becoming involved with Marxist groups. There were at least four Marxist groups in Afghanistan at the time; two of the four were established by Karmal.