Cuba's involvement in the Angolan Civil War began in the 1960s, when relations were established with the leftist Movement for the Popular Liberation of Angola (MPLA). The MPLA was one of three organisations struggling to gain Angola's independence from Portugal, the other two being UNITA and the National Liberation Front of Angola (FNLA). In August and October 1975, the South African Defence Force (SADF) intervened in Angola in support of the UNITA and FNLA (Operation Savannah). Cuban troops began to arrive in Angola in early October 1975. On 6 October, Cubans and the MPLA clashed with the FNLA and South African troops at Norton de Matos and were badly defeated. The Cubans blocked an advancing South African mechanized column on 4 November with 122mm rocket fire, causing the South Africans to request heavy artillery which could out-distance the rockets. Castro reacted to the presence of the South African armored column by announcing Operation Carlota, a massive resupply of Angola, on 5 November.