By 1978 Amin's circle of close associates had shrunk significantly--the result of defections and executions. It was increasingly risky to be too close to Amin, as his vice president and formerly trusted associate, General Mustafa Adrisi, discovered. When Adrisi was injured in a suspicious auto accident, troops loyal to him became restive. The once reliable Malire Mechanized Regiment mutinied, as did other units. In October 1978, Amin sent troops still loyal to him against the mutineers, some of whom fled across the Tanzanian border. Amin then claimed that Tanzanian President Nyerere, his perennial enemy, had been at the root of his troubles. Amin accused Nyerere of waging war against Uganda, and, hoping to divert attention from his internal troubles and rally Uganda against the foreign adversary, Amin invaded Tanzanian territory and formally annexed a section across the Kagera River boundary on November 1, 1978.
Nyerere mobilized his citizen army reserves and counterattacked, joined by Ugandan exiles united as the Uganda National Liberation Army (UNLA). The Ugandan Army retreated steadily, expending much of its energy by looting along the way. Libya's Qadhafi sent 3,000 troops to aid fellow Muslim Amin, but the Libyans soon found themselves on the front line, while behind them Ugandan Army units were using supply trucks to carry their newly plundered wealth in the opposite direction. Tanzania and the UNLA took Kampala in April 1979, and Amin fled by air, first to Libya and later to a seemingly permanent exile at Jiddah, Saudi Arabia. The war that had cost Tanzania an estimated US$1 million per day was over.
In the fall of 1978, Ugandan troops, under orders from dictatorial president-for-life Idi Amin (1925-), invaded northern Tanzania and, after blowing up the only bridge over the Kagera River, occupied about 700 square miles of foreign territory, called the Kagera Salient. In response, President Julius K. Nyerere (1922-) of Tanzania sent an army, reinforced by Ugandan exiles who had fled their homeland to escape Amin's tyrannical rule, across the border into Uganda (October 1978). Soon the invaders were advancing through southern Uganda after winning some skirmishes. They surrounded the Ugandan capital of Kampala, but were halted briefly by a Libyan force that had come to Amin's aid. On April 11, 1979, Tanzanian troops and Ugandan exiles and nationalists entered Kampala, whose residents welcomed them as liberators. Eluding capture, Amin fled to Libya and left behind an impoverished Uganda and a brutalized people. During the eight years of his rule, he had expelled all Asians, killed thousands of tribespeople and Christians, spent excessively to build up his army, and nationalized all land without compensating the owners.