By 1980, hopes for a rapid transition to independence had collapsed. South Africa refused to engage fully with the United Nations process, and talks on implementing Resolution 435 reached an impasse in 1981 that lasted for most of the decade. The question was no longer simply whether Namibia would be decolonised, but when and under what regional conditions.

Military developments in southern Angola eventually altered the diplomatic balance. In 1985 and again in August 1987, Angolan forces supported by Soviet and Cuban assistance advanced from Cuito Cuanavale toward UNITA’s main logistical base at Mavinga. The offensives were pushed back by UNITA with strong South African and US support, but the resulting stalemate encouraged negotiations.

By 1988, the Angolans and their allies were prepared to consider ‘linkage’: South African withdrawal from Namibia would occur together with Cuban withdrawal from Angola. Negotiations on implementing Resolution 435 began in London in May 1988. At the same time, Cuban forces moved 15,000 troops north of the Angolan border with Owambo, creating a military pressure that helped persuade South Africa to proceed.

Resolution 435/1978 was eventually implemented in 1989, leading to independence for Namibia in 1990. The settlement emerged from diplomacy, military exhaustion, international pressure and the rising costs of the regional war rather than from a single decisive military victory.