While still in his teens, Koreta attended military training in Mozambique as a member of the Front for National Salvation, a guerilla group led by Yoweri Museveni. He participated in the war that removed Idi Amin from power in 1979. When Museveni formed the National Resistance Army (NRA) in 1981, Koreta joined him. During the Ugandan Bush War, he became a battalion commander in the NRA. During the April 1986 battle to capture the Ugandan capital city Kampala, his 13th NRA Battalion was responsible for guarding the Kampala-Gulu highway at Matugga.