Mengistu Haile Mariam was the leader of Ethiopia from 1974 to 1991, serving as a prominent figure in the Derg, a Marxist-Leninist military junta that established a socialist state in Ethiopia. His regime is significant in the context of the spread of communism after 1900, as it exemplifies how communist ideologies influenced governance in Africa during the Cold War, leading to both internal repression and international alignments.