Portugal's primary interest in Angola quickly turned to slavery. The slaving system began early in the 16th century with the purchase from African chiefs of people to work on sugar plantations in Sao Tome, Principe, and Brazil. Many scholars agree that by the 19th century, Angola was the largest source of slaves not only for Brazil, but for the Americas, including the United States. By the end of the 19th century, a massive forced labor system had replaced formal slavery and would continue until outlawed in 1961. It was this forced labor that provided the basis for development of a plantation economy and, by the mid-20th century, a major mining sector. Forced labor combined with British financing to construct three railroads from the coast to the interior, the most important of which was the transcontinental Benguela railroad that linked the port of Lobito with the copper zones of the Belgian Congo and what is now Zambia.

Colonial economic development did not translate into social development for native Angolans. The Portuguese regime encouraged white immigration, especially after 1950, which intensified racial antagonisms. As decolonization progressed elsewhere in Africa, Portugal, under the Salazar and Caetano dictatorships, rejected independence and treated its African colonies as overseas provinces. Consequently, three independence movements emerged: the Popular Movement for the Liberation of Angola (MPLA), with a base among Kimbundos and the mixed-race intelligentsia of Luanda, and links to communist parties in Portugal and the East Bloc; the National Liberation Front of Angola (FNLA), with an ethnic base in the Bakongo region of the north and links to the United States and the Mobutu regime in Kinshasa; and the National Union for the Total Independence of Angola (UNITA), led by Jonas Malheiro Savimbi with an ethnic and regional base in the Ovimbundo heartland in the center of the country.

From the early 1960s, elements of these movements fought against the Portuguese. A 1974 coup d'etat in Portugal established a military government that promptly ceased the war and agreed to hand over power to a coalition of the three movements. The coalition quickly broke down and turned into a civil war. By late 1975, Cuban forces had intervened on behalf of the MPLA and South African troops for UNITA, effectively internationalizing the Angolan conflict. In control of Luanda and the coastal strip (and increasingly lucrative oil fields), the MPLA declared independence on November 11, 1975, the day the Portuguese abandoned the capital. Augustinho Neto became the first president, followed by Jose Eduardo dos Santos in 1979.

Civil war between UNITA and the MPLA continued until 1989. For much of this time, UNITA controlled vast swaths of the interior and was backed by U.S. resources and South African troops. Similarly, tens of thousands of Cuban troops remained in support of the MPLA, often fighting South Africans on the front lines. A U.S.-brokered agreement resulted in withdrawal of foreign troops in 1989 and led to the Bicesse Accord in 1991, which spelled out an electoral process for a democratic Angola under the supervision of the United Nations. When UNITA's Jonas Savimbi failed to win the first round of the presidential election in 1992 (he won 40% to Dos Santos's 49%, which meant a runoff), he called the election fraudulent and returned to war. Another peace accord was brokered in Lusaka, Zambia, signed in 1994. This agreement, too, collapsed in 1998 when Savimbi renewed the war for a second time, claiming the MPLA was not fulfilling its obligations. The UN Security Council voted on August 28, 1997, to impose sanctions on UNITA. The Angolan military launched a massive offensive in 1999 which destroyed UNITA's conventional capacity and recaptured all major cities previously held by Savimbi's forces. Savimbi then declared a return to guerrilla tactics, which continue to keep much of the country in turmoil. The prospect is for continued low-level guerrilla warfare that will keep much of the country insecure.