political dissent included the military police and the Public Safety Unit (PSU).
Obote took refuge in Tanzania, having been offered sanctuary there by Tanzanian President Julius Nyerere. He was soon joined by 20,000 Ugandan refugees fleeing Amin. In 1972, the exiles attempted to regain the country through a poorly organized coup attempt, without success.
Persecution of ethnic and other groups
Amin retaliated 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. In July 1971, Lango and Acholi soldiers were massacred in the Jinja and Mbarara Barracks, and by early 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,