From UNHCR, Vieira de Mello moved to the field in Bangladesh during its War of Independence in 1971, and Sudan in 1972 following the Addis Ababa agreement which ended the First Sudanese Civil War and allowed the return of some 650,000 Sudanese refugees and displaced persons, and Cyprus after the Turkish part of Cyprus in 1974. These early assignments were operational, rather than political; he was helping to organize food aid, shelter and other types of aid to refugees. Sergio remained in the field, with a posting in Mozambique to assist refugees fleeing white rule and civil war in Zimbabwe (at the time, still Rhodesia) where he was deputy head of the office. Due to the absence of his boss, he was effectively running the mission.