
Lacking strong domestic backing, the MPLA looked abroad for military and economic support. Its leftist revolutionary agenda naturally aligned the MPLA with communist nations and the Soviet Union and Cuba became the movement’s strongest allies, with the Soviets providing material aid, money, and weapons and the Cubans eventually sending soldiers to assist with security and military campaigns.  Other communist countries in Eastern Europe also supplied arms and military advisors, including the German Democratic Republic (East Germany). 
Support from other African countries was more limited. Neighboring Zaire and South Africa actively backed the FNLA and UNITA, both committing significant numbers of soldiers to fight the MPLA. Other African nations were less hostile; during the independence war the organization was based at different times in Congo-Brazzaville, Tanzania, and Zambia. Tanzania and Zambia also served as transit points for incoming Soviet arms shipments.
Though a relatively unified group during most of the civil war, divisions within the MPLA threatened its existence in its early years and into the 1970s. At the root of the inner factionalism was the disparate backgrounds of MPLA members, which included both educated mesticos and assimilados as well as uneducated peasants. Various groups formed factions that struggled for dominance within the movement. One major split was the Eastern Revolt led by Daniel Chipenda in the early-1970s, which set the guerillas doing most of the fighting against the political organization led by Agostihno Neto in Luanda. Chipenda eventually joined the FNLA and helped elicit the support of South Africa in the war against his old organization.
The Frente Nacional de Libertação de Angola (National Front for the Liberation of Angola) grew out of the UPA (Union of Peoples of Angola, previously Union of Peoples of Northern Angola), a predominately Bakongo movement based in northern Angola and led by Holden Roberto. While the MPLA had its origins in Lisbon and Luanda, the UPA was founded in Léopoldville (modern Kinshasa) in neighboring Congo, also home to a large Bakongo population. In the late 1950s and 60s, Léopoldville was a center of nationalist activism, hosting a large refugee community from Angola and over fifty Angolan political organizations, mostly made up of Bakongos. Unlike the ideologically based MPLA, the UPA and other Bakongo nationalist movements appealed directly to the Bakongo ethnic group and the heritage of the old Kongo kingdom.  Though Holden Roberto had ambitions of making the UPA/FNLA a nation-wide movement with broad-based support, it remained for most of its history an organization dominated by Bakongos, and was responsible for numerous acts of violence against mestiços, assimilados, whites, and non-Bakongo Africans, particularly the Ovimbundu who worked on the coffee plantations of the north. 
Its reputation for violence and the lack of discipline among its ranks led many to distrust the FNLA, and greatly decreased its effectiveness. Infighting plagued the organization throughout its history as well.  According to John Stockwell, chief of the CIA’s Angola Task  Force in 1975, the FNLA “had few educated men at the top—no intellectuals—and had spent much of its history in the cocktail parties of Kinshasa. 