The victims of Amins reign all begun with him retaliating against the attempted invasion by Ugandan exiles in 1972 by purging the army of Obote supporters, predominantly those from the Acholi and Lango ethnic groups. Lango and Acholi soldiers were massacred in the Jinja and Mbarara Barracks and by 1972, some 5,000 Acholi and Lango soldiers, and at least twice as many civilians, had disappeared. The victims soon came to include members of other ethnic groups, religious leaders, journalists, artists, senior bureaucrats, judges, lawyers, students and intellectuals, criminal suspects, and foreign nationals. In this atmosphere of violence, many other people were killed for criminal motives or simply at will. Bodies often dumped into the Nile River.
The killing, motivated by ethnic, political, and financial factors, was prolonged throughout Amin's eight-year reign. The exact number of people killed is unknown. The International Commission of Jurists estimated the death toll at no fewer than 80,000  Among the most prominent people killed were Benedicto Kiwanuka, the former Prime Minister and Chief Justice; Janani Luwum, the Anglican archbishop; Joseph Mubiru, the former governor of the Central Bank; Frank Kalimuzo, the vice chancellor of Makerere University; Byron Kawadwa, a prominent playwright; and two of Amin's own cabinet ministers, Erinayo Wilson Oryema and Charles Oboth Ofumbi.
In late 1972, Amin declared what he called an "economic war", a set of policies that included the expropriation of properties owned by Asians and Europeans. Uganda's 80,000 Asians were mostly from the Indian subcontinent and born in the country, their ancestors having come to Uganda when the country was still a British colony. Amin issued a decree ordering the expulsion of the 60,000 Asians who were not Ugandan citizens. Which was later amended to include all 80,000 Asians, not including professionals, such as doctors, lawyers, and teachers. A plurality of the Asians with British passports, around 30,000, emigrated to the UK. Others went to Australia, Canada, India, Kenya, Pakistan, Sweden,Tanzania, and the U.S. Amin expropriated businesses belonging to the Asians and handed them over to his supporters.
The killings took place over his eight year reign from the 25th of January 1971 to the 11th of April 1979.