Key Point: The Republic of South Africa felt safer by disarming.
Why did South Africa decide to build nukes, how did it build them and why did it decide to give them up? The answers are largely idiosyncratic, although they may hold some lessons for the future of nuclear weapons development on the Korean Peninsula and elsewhere.
Origins of Program
South Africa sought nuclear weapons for familiar reasons. Although it enjoyed presumptive conventional dominance over any likely regional opponent, Pretoria worried that the advantage might erode over time. The South African government also appreciated that widespread disdain for its apartheid system might prevent Western countries (including the United States) from coming to its aid in any serious confrontation against the Soviet Union or its allies. Nuclear weapons would provide not only a direct way of confronting a military attack against South Africa, but also a means of leveraging Western diplomatic and military support during a crisis.
South Africa could mine the requisite uranium on its own territory, and enrich it in domestic facilities. With a modern industrial economy and access to technologically sophisticated institutions of learning and research in the United States and Europe, South Africa could easily develop the technical expertise needed to build a weapon. Already the target of harsh international disdain for its domestic institutions, the South African government did not worry overmuch about how the pursuit of nuclear weapons might make it into an international pariah.
Overall, South Africa constructed six uranium gun fission weapons (similar in nature to the Little Boy weapon dropped on Hiroshima). The devices were too large to fit onto any existing South African missiles, and consequently would have been delivered by bombers such as the English Electric Canberra or the Blackburn Buccaneer. South Africa explored the possibility of building or acquiring ballistic missiles capable of carrying nuclear weapons, although this would have required a substantial upgrade of the devices themselves. No full test of the devices has ever been confirmed, as heavy pressure from the United States, the Soviet Union and France helped force Pretoria to cancel an underground detonation in 1977.