Born in the Congo, Maliyamungu was one of the members of the 1971 coup that brought Amin to power, and was thereafter responsible for brutally suppressing dissidents throughout the country.

As the Ugandan military dictatorship weakened and Amin's support eroded among the country's masses and elite, Maliyamungu was one of his few remaining trusted confidants.

After the Uganda–Tanzania War's outbreak in 1978, Maliyamungu held important military commands, but had little success in combat against the Tanzania People's Defence Force.

[14][19] After the successful coup, Maliyamungu was one of the officers who were entrusted with defeating the remaining militant Obote loyalists and purging the Uganda Army of anti-Amin elements.

[29] Most importantly of all his commands, Maliyamungu headed the VIP Protection Unit (Amin's bodyguards and enforcers)[30] and played a major role in the State Research Bureau, Uganda's intelligence agency.

[6] Knowing that his power derived from his influence over the soldiers, Maliyamungu reportedly turned down offers of cabinet posts to stay in the barracks.

He was generally respected and feared among the common soldiers,[6] and held the power to beat or execute those who disappointed him[34] or were suspected of being disloyal to the Amin regime.

They discussed plans by Israel to carry out a raid against Entebbe to free hostages who were held there by Palestinian and German hijackers with assistance by the Ugandan government.

[36][c] That same day, Israeli commandos carried out Operation Entebbe, freeing the hostages, and destroying one quarter of the Uganda Army Air Force.

[39] Over time, Amin's brutal regime was increasingly destabilized by internal divisions and economic problems despite great repression by state authorities.

[40] One of Amin's policies that drew opposition even among his original followers was the great power he gave to Kakwa and Nubians, while leaving officials of other ethnicies underrepresented.

As result, a group of officers led by Brigadier Charles Arube attempted to overthrow Amin and kill his Nubian/Kakwa followers, including Maliyamungu.

[3] According to Mustafa Adrisi (Vice President of Uganda at the time)[59] and a Human rights commission, Maliyamungu was directly responsible for their deaths.

[15] Intelligence reports also implicate him in the killing of Kung'u Karumba, a friend of Prime Minister of Kenya Jomo Kenyatta and a prominent Kenyan nationalist.

[61] Despite the widespread and brutal suppression of all dissidents, the power of the Amin regime increasingly deteriorated in the late 1970s, as political and economic instability grew in Uganda.

In response to these developments, Maliyamungu (by then promoted to brigadier) declared in a 1978 speech to 10,000 civilians that he would use tanks and bulldozers to destroy any area that was opposed to the government, proving to everyone that the regime "is hotter than a heated iron bar and not afraid to act".

In late 1975 he interrupted a session of the Uganda Amateur Athletics Association (UAAA) general assembly and declared his desire to lead the organisation.

The Ugandan Invasion of Kagera was repelled by November 1978, as the Tanzania People's Defence Force (TPDF) launched a large-scale counter-offensive.

[69] By February 1979, Maliyamungu was in command of the garrison at Masaka, which was one of the most important towns in southern Uganda, and thus became a target of the advancing Tanzanian troops.

[72][71] Maliyamungu got lost in the bush for more than a week following the battle at Masaka;[73] according to journalist Felix Ocen, he feared reprisals for his defeat, and eventually returned with an apology.

[74] It was planned that the Ugandans and allied Libyan forces would first retake Lukaya, and then attack Masaka with the ultimate aim of expelling the TPDF from Uganda.

[74][10] Whereas Msuya praised him for smartly executing the initial Ugandan attack which resulted in the rout of the Tanzanian 201st Brigade and capture of Lukaya,[74] Idi Amin's son Jaffar Rembo Amin later claimed that Maliyamungu had been bribed by the Tanzanians to lose the battle, and also accused him of cowardice for placing his command position miles from the frontlines.

The leading Ugandan commander at Lukaya, Godwin Sule, realised the generals were not having a positive effect and asked them to leave the front.

[6] In regard to his brutal suppression of dissidents, historian Richard J. Reid described Maliyamungu as "possibly psychotic",[23] while researcher Samuel Decalo called him "a notoriously sadistic killer".

[88] Both informal narratives and academic works often use him as an example of the foreign "mercenaries" employed by Amin's regime and often imply that his violent behaviour could be explained by either his non-Ugandan origin or his allegedly "psychotic" mental state.