Angola has been a physical and ideological battleground since Portugal abruptly abandoned its 500-year colonial rule in 1975 and left African nationalist groups backed by outsiders to fight it out for control of this potentially wealthy nation of about 7 million inhabitants.

Aided by a massive Soviet arms airlift and the arrival of Cuban troops, the Popular Movement for the Liberation of Angola (MPLA) prevailed over Jonas Savimbi's UNITA (Union for the Total Independence of Angola) and over Holden Roberto's FNLA (National Front for the Liberation of Angola). Roberto received direct, significant support from South Africa, Zaire and the Central Intelligence Agency. South African units invaded from the south with Savimbi's assistance.

Roberto's organization appears to have ceased to be an active threat. But Savimbi has been able to regroup UNITA, again with South African help, and has mounted an increasingly effective guerrilla war of economic sabotage nationally and has overrun government outposts throughout the remote southeastern reaches of the country.

The MPLA's national Army is reliably estimated to number around 60,000 soldiers. The armed men under Savimbi's control are estimated at 20,000, and the UNITA leader claims to have control over 2 million Angolans living in the areas where his men operate. Government officials dismiss these estimates as grossly exaggerated, and they decline to discuss the size of their Army or of the Cuban expeditionary force.

Angola's border with Namibia, a former German colony mandated by the League of Nations to South African control after World War II, has also been the source of conflict. Several thousand armed guerrillas belonging to the South West African People's Organization (SWAPO) operating around the border area have been engaged in an insurgency against the South African Army for nearly two decades.

South Africa has cited the presence of SWAPO guerrillas in Angola as justification for two major invasions since the independence war, in 198l and 1983.

The United Nations has ordered South Africa to grant independence to Namibia and has outlined its terms for a settlement in Security Council Resolution 435. The United States has participated in a five-power effort to get South Africa to agree to implement the resolution, stage a phased withdrawal from the territory and accept U.N. supervision of elections for an independent government.

Acting on a suggestion originally put forward by the Reagan administration, the South African governmnent has now linked its willingness to pull out of Namibia to a withdrawal of the Cuban forces from Angola. An impasse has developed over this point. Recent informal suggestions from South Africa, that Savimbi must be reconciled in the national government before a regional accord can be reached, have raised concern in Luanda that new sticking points are developing.