South Africa's interest in Angolan affairs began during the Portuguese colonial period, especially after 1966 when the insurgency spread to the east. South Africa's military and intelligence services cooperated closely with those of Portugal. South Africa and Portugal opened a joint command center ÍÍÍin Cuito Cuanavale in southeast Angola in 1968, and from there South African troops participated in actions against Angolan nationalist guerrillas as well as against southern Angola-based guerrillas of the South West Africa People's Organization (SWAPO), the Namibian group fighting for independence from South African rule.

The collapse of Portugal's empire and the prospect of black rule in Angola (and Mozambique) caused enormous concern in Pretoria. Especially troubling to the South African government was the leftist orientation of several of these nationalist movements. Thus, in August 1975 South African military forces came to the aid of the FNLA-UNITA alliance and occupied the Ruacaná hydroelectric complex and other installations on the Cunene River. On October 23, a force of 300 South African troops, assisted by about 3,000 South African-trained Angolans, invaded Angola. They advanced rapidly north for nearly 1,000 kilometers and came within 100 kilometers of Luanda. This force was later increased to as many as 10,000, but most of these troops were Angolans under South Africa's military command.

The South African invasion had several international consequences. It prompted a massive increase in the flow of Soviet military supplies to the MPLA and caused Cuba to send thousands of men to Angola in defense of the government. Moreover, because the United States was supporting the same factions as the South African regime, the United States involvement drew harsh criticism from the international community. Furthermore, many African countries that until then had opposed the MPLA, including Nigeria, Tanzania, Ghana, and Sudan, reversed themselves and recognized the MPLA government.

Data as of February 1989