Between 1975 and 1987, the Derg executed and imprisoned tens of thousands of its opponents without trial.
The Coordinating Committee of the Armed Forces, Police, and Territorial Army, or the Derg (Committee), was formed in June 1974 by military officers following widespread mutiny in the armed forces of Ethiopia in early 1974. The number of committee members was originally about 120. No new members were ever admitted, and the number decreased, especially in the first few years, as some members were expelled or killed. The committee elected Major Mengistu Haile Mariam as its chairman and Major Atnafu Abate as its vice-chairman. The Derg was initially supposed to study the grievances of various military units, and investigate abuses by senior officers and staff, and to root out corruption in the military.
In the months following its founding, the power of the Derg steadily increased. In July the Derg obtained key concessions from the Emperor, Haile Selassie. This included the power to arrest not only military officers, but government officials at every level. Soon both former Prime Ministers Tsehafi Taezaz Aklilu Habte-Wold, and Endelkachew Makonnen, along with most of their cabinets, most regional governors, many senior military officers and officials of the Imperial court found themselves imprisoned. In August, after a proposed constitution creating a constitutional monarchy was presented to the Emperor, the Derg began a program of dismantling the imperial government in order to forestall further developments in that direction. The Derg deposed and imprisoned the Emperor on September 12, 1974.
On September 15, the committee renamed itself the Provisional Military Administrative Council (PMAC) and took control of the government. The Derg chose Lieutenant General Aman Andom to be its chairman and acting head-of-state until the Crown Prince Asfaw Wossen could return from his medical treatment in Europe, and assume the throne as a constitutional monarch. However, General Aman Andom quarreled with the radical elements in the Derg over the issue of a new military offensive in Eritrea and the proposal to execute the high officials of the Emperor's former government. After eliminating units loyal to him -- the Engineers, the Imperial Bodyguard and the Air Force -- the Derg removed General Aman from power and executed him along with some supporters and 60 officials of the previous Imperial government on November 24, 1974. Brigadier General Tafari Benti became both the new Chairman of the Derg and head of state, with Mengistu and Atnafu Abate as his two vice-Chairman with the new ranks of Lieutenant-Colonels. The monarchy was formally abolished in May, 1975, and Marxism-Leninism was proclaimed the ideology of the state. Emperor Haile Selassie died on August 22, 1975. The circumstances of his death continue to be the subject of much speculation.
After internal conflicts, that resulted in the deaths of General Tafari Benti and several of his supporters by November 1977, and the later elimination and execution of Colonel Atnafu Abate, Mengistu gained undisputed leadership of the Derg. In 1987 the Derg was formally dissolved and the country became the People's Democratic Republic of Ethiopia (PDRE) under a new constitution. Many of the Derg members remained in key government posts, and remained as the members of the Central Committee and the Politburo of the Workers' Party of Ethiopia (WPE), which became Ethiopia's civilian version of the Eastern bloc Communist parties. Mengistu became Secretary General of the WPE, President of the PDRE, while remaining Commander in Chief of the Armed Forces.
The reign of the Derg in Ethiopia is remembered as giving rise to the Ethiopian Civil War. This conflict began as extralegal violence between 1975 and 1977, known as the Red Terror, when the Derg struggled for authority, first with various opposition groups, then with a variety of groups jockeying for the role of vanguard party. Brutal tactics were used by both sides, including executions, assassinations, tortures and imprisonment of tens of thousands without trial. Once the Derg had gained victory over these groups, then successfully fought off an invasion from Somalia in 1977, it engaged in a brutal war between the government and armed groups which included guerrillas fighting for Eritrean independence, rebels based in Tigray (which included the nascent Tigrayan Peoples' Liberation Front), and other groups that ranged from the conservative and pro-monarchy Ethiopian Democratic Union to the far leftist Ethiopian People's Revolutionary Party. Ethiopia under the Derg became the Socialist bloc's closest ally in Africa, and became among the best armed nations of the region as a result of massive military aid chiefly from the Soviet Union, GDR, Cuba and North Korea.
During the same period, the Derg fulfilled its main slogan of "Land to the Tiller" by announcing on 4 March 1975 a system of land reform that "was unequivocally radical, even in Soviet and Chinese terms; it nationalized all rural land, abolished tenancy, and put peasants in charge of enforcing the whole scheme. Although the Derg had little respect during its rule, this one act resulted in a rare show of support for the junta, as the Ottaways describe: "During a massive demonstration in Addis Ababa immediately following the announcement, a group of students broke through police and army barriers, climbed the wall and escarpment around Menelik Palace, and embraced major Mengistu as the hero of the reform". Most industries and private urban real-estate holdings were nationalized by the Derg in 1975.
However, mismanagement, corruption, and general hostility to the Derg's violent rule, coupled with the draining effects of constant warfare with the separatist guerrilla movements in Eritrea and Tigray, led to a drastic fall in general productivity of food and cash crops. In October 1978, the Derg announced the National Revolutionary Development Campaign to mobilize human and material resources to transform the economy, which led to a Ten Year Plan (1984/85-1993/94) to expand agricultural and industrial output, forecasting a 6.5% growth in GDP and a 3.6% rise in per capita income; instead, per capita income declined 0.8% over this period. Although Ethiopia is prone to chronic droughts, no one was prepared for the scale of drought and famine that struck the country in the mid-1980s, in which up to a million may have died. Hundreds of thousands fled economic misery, conscription, and political repression, and went to live in neighboring countries and all over the Western world, creating an Ethiopian diaspora for the first time.
The famine in the mid 1980s brought the situation in Ethiopia to the attention of the world, and inspired charitable drives in western nations, notably by Oxfam and the Live Aid concerts of July 1985. Funds raised by Oxfam and Live Aid was distributed among NGOs in Ethiopia. A controversy arose when it was revealed that some of these NGOs were under Derg control or influence, and that some Oxfam and Live Aid money had been used to fund the Derg's enforced resettlement programmes, under which millions of people were displaced and between 50,000 and 100,000 killed.
The Derg government officially came to an end in 1987 upon the formation of the PDRE. Mengistu remained in power as President of the new government.
The geopolitical situations turned unfavorable in the late 1980s, with the Soviet Union retreating from World Communism under Mikhail Gorbachev's glasnost and perestroika, marked a dramatic reduction in aid from Socialist bloc countries. This resulted in even more economic hardship, and more seriously, the collapse of the military in the face of determined onslaughts by guerrilla forces in the north. The Soviet Union, on the verge of collapse itself coupled with rapidly losing the Cold War, stopped aiding the PDRE altogether in December 1990, and this along with the collapse of Communism in the Eastern Bloc in the Revolutions of 1989, proved to be serious blows to the PDRE.
Towards the end of January 1991, a coalition of rebel forces, the Ethiopian People's Revolutionary Democratic Front (EPRDF), launched Operation Tewodros, which led to their capture of Gondar, the ancient capital city, Bahar Dar and Dessie. Meanwhile, the Eritrean People's Liberation Front had gained control of all of Eritrea except for Asmara and Assab in the south. The Soviet Union, mired in its internal turmoil, did not step in to prop up the Derg; it was clear that the end of the Derg was now a question of when, not if. In the words of the former US diplomat Paul B. Henze, "As his doom became imminent, Mengistu alternated between vowing resistance to the end and hinting that he might follow Emperor Tewodros's example and commit suicide." His actions were frantic: he convened the Shengo or Ethiopian Parliament, for an emergency session and reorganized his cabinet, but as Henze concludes, "these shifts came too late to be effective. On 21 May, claiming that he was going to inspect troops at a base in southern Ethiopia, Mengistu slipped out of the country to Kenya, then proceeded to Zimbabwe, where he was granted asylum and as of 2007 still resides. The EPRDF immediately disbanded the WPE and arrested almost all of the prominent Derg officials shortly after.
In December 2006, 72 officials of the Derg were found guilty of genocide. Thirty-four people were in court, 14 others have died during the lengthy process and 25, including Mengistu, were tried in absentia.