What is "ruanda-urundi"

Ruanda-Urundi was a territory in the African Great Lakes region, once part of German East Africa, which was ruled by Belgium between 1916 and 1962. Occupied by the Belgians during the East African Campaign during World War I, the territory was under Belgian military occupation from 1916 to 1922 and later became a Belgian-controlled Class B Mandate under the League of Nations from 1922 to 1945. After the disestablishment of the League and World War II, Ruanda-Urundi became a Trust Territory of the United Nations, still under Belgian control. In 1962, the mandate became independent as the two separate countries of Rwanda and Burundi.