 Complete the following phrase:  The MPLA and Cubans would maintain the initiative in Northern Angola after the defeat of the FNLA at Quifangondo with the advances on Caxito and the latters airbases at Camabatela and Negage. Caxito would fall on 27 December 1975 and the FNLAs main airbase at Camabatela was captured on 1 January and Negage on 3 January while their capital at Carmona fell on 4 January and so the FNLA rout began in earnest. By early 1976, defeated by the MPLA, the FNLA began retreating, looting villages in northern Angola, as they headed for the Zairian border. On 11 January 1976, FAPLA and the Cubans captured Ambriz and Ambrizete from the FNLA and then advanced on their headquarters at São Salvador its route defended by foreign mercenaries under Colonel Callan and elements of the FNLA. With Colonel Callan committing atrocities in the fighting including against his own men he would be stripped of his command in the FNLA and so mercenary support which had begun the previous December ended and São Salvador was captured on 15 February 1976. The South Africans would withdraw from Angola on 27 March 1976 after receiving guarantees from Angola and United Nations on the safety of the installations at the Calueque hydroelectric facility so ending 