Excerpts from Books and Wikipedia
"However, the position of the British Labor government, and much of the population was that this was an act of rebellion, and Rhodesian independence would never be recognized until democracy held sway. . . . Sanctions had little immediate effect. Rhodesia enjoyed the support of Portugal, which was determined to defy African nationalists and hold on to its neighboring colony of Mozambique. The South African government, also, saw Rhodesia as a bulwark protecting its own apartheid regime from African nationalism. But in 1975 Mozambique became independent, and South Africa, suffering sanctions and internal African opposition, was unable to subsidize Rhodesia any longer. By 1979, isolated and exposed, the white minority had no option but to negotiate their submission to majority rule." [Furtado: 1001 Days]