Mercenaries fought for the Biafrans in the 4th Commando Brigade during the Nigerian Civil War, (1967–1970). Other mercenaries flew aircraft for the Biafrans. In October 1966, for example, a Royal Air Burundi DC-4M Argonaut, flown by a mercenary Heinrich Wartski also known as Henry Wharton, crashlanded in Cameroon with military supplies destined for Biafra.

In the mid-1970s John Banks, a Briton, recruited mercenaries to fight for the National Front for the Liberation of Angola FNLA against the Popular Movement for the Liberation of Angola (MPLA) in the civil war that broke out when Angola gained independence from Portugal in 1975. When captured, John Derek Barker's role as a leader of mercenaries in Northern Angola led the judges to send him to face the firing squad. Nine others were imprisoned. Three more were executed: American Daniel Gearhart was sentenced to death for advertising himself as a mercenary in an American newspaper; Andrew McKenzie and Costas Georgiou (the self styled "Colonel Callan"), who had both served in the British army, were sentenced to death for murder.

American Bob MacKenzie was killed in the Malal Hills in February 1995 while commanding Gurkha Security Guards (GSG) in Sierra Leone. GSG pulled out soon afterwards and was replaced by Executive Outcomes. Both were employed by the Sierra Leone government as military advisers and to train the government soldiers. It has been alleged that the firms provided solders who to an active part in the fighting against the Revolutionary United Front (RUF).

In August 2004 there was the a plot to overthrow the government of Equatorial Guinea in Malabo. It was planned, it is alleged, by Simon Mann (a founder of Executive Outcomes) a former SAS officer. On 27 August 2004 he was found guilty in Zimbabwe of purchasing arms, allegedly for use in the plot. (He admitted trying to procure dangerous weapons, but said that they were to guard a diamond mine in DR Congo.) It is alleged that there is a paper trail from him which implicates Sir Mark Thatcher, Lord Archer and Ely Calil (a Lebanese-born oil trader).

Currently eight South African apartheid-era soldiers (the leader of whom is Nick du Toit), six Armenian aircrew and five local men are in Black Beach prison on the island. They are accused of being an advanced guard for a coup to place Severo Moto in power.