South Arabia, Federation of, federation, 1963–67, S Arabian peninsula, formed by the merger of the British colony of Aden with the Federation of the Emirates of the South, a British protectorate. The Federation of the Emirates of the South was formed (Feb., 1959) by the union of six emirates, sultanates, and sheikhdoms; by the end of 1960 there were 10 members. In Jan., 1963, the Aden colony joined the federation, which was then renamed the Federation of South Arabia. The British-sponsored federation met with considerable opposition from the people of Aden, who feared domination by the conservative tribal states. Two rival nationalist groups emerged in the aftermath of the federation—the National Liberation Front (NLF) and the Front for the Liberation of Occupied South Yemen (FLOSY). By late 1967 the NLF had become the dominant group and forced the collapse of the federal government. British forces were withdrawn in Nov., 1967, and Aden and South Arabia became the independent state of South Yemen (see Yemen). South Yemen and (northern) Yemen united as a single nation in 1990.