1974年9月，由于一批少壮军官组成”军队、警察和地方军协调委员会"(即DERGUE,英文SHADOW之意，后泛指军政府和门格斯图政权)发动军事政变，推翻海尔·塞拉西政府，宣布结束帝制，成立”临时军政府”。11月，”临时军政府”又改为"临时军事行政委员会"。12月，"临时军事行政委员会"宣布埃塞俄比亚为"社会主义国家",实行土地、金融财政机构和工业国有化。
Lt. Col. Mengistu Haile Mariam assumed power as head of state and Derg chairman, after having his two predecessors killed, as well as tens of thousands of other suspected opponents. The new Marxist government undertook socialist reforms, including nationalisation of landlords' and church's property. Before the coup, Ethiopian peasants' way of life was thoroughly influenced by the church teachings; 280 days a year are religious feasts or days of rest. Mengistu's years in office were marked by a totalitarian-style government and the country's massive militarization, financed by the Soviet Union and the Eastern Bloc, and assisted by Cuba. In December 1976, an Ethiopian delegation in Moscow signed a military assistance agreement with the Soviet Union. The following April, Ethiopia abrogated its military assistance agreement with the United States and expelled the American military missions.