The Provisional Military Government of Socialist Ethiopia, nicknamed the Derg, was the communist military junta which ruled Ethiopia from 12 September 1974 to 22 February 1987. The Derg was established by a junta of socialist military officers following their overthrow of the Ethiopian Empire in a 1974 coup d'etat, and it was led by army, air force, navy, Imperial Guard, Territorial Army, and police chiefs at its onset. The Derg abolished the monarchy and created a Marxist-Leninist one-party state with itself as the sole legal party, and it also abolished feudalism, increased literacy, nationalized major industries, and enacted sweeping land reforms. In 1977, Mengistu Haile Mariam became the Derg's Chairman, initiating a period of "Red Terror" to suppress popular discontent amid the Ethiopian Civil War. Tens of thousands were arrested, imprisoned, and executed without trial, and the humanitarian situation was further exacerbated by a famine from 1983 to 1985 which killed over 1 million people. The famine, the Red Terror, and the Derg's mismanagement of the country led to the ethnic separatist movements gaining strength, and, in 1987, Mengistu abolished the Derg and replaced it with the People's Democratic Republic of Ethiopia in a bid to confer legitimacy upon Ethiopia's communist rulers as a civilian government.