Sanctions against South Africa have been in place for a while, (UN condemnation in 1962, banning of arms sales in 1963); in the 1980s, sanctions increased from powerful nations to pressure governments into changing their actions
Pressure had also been on certain governments, e.g. the UK, from the Anti-Apartheid Movement - worked with the International Defence and Aid Fund
US Anti-Apartheid Act, 1986; caused severe economic strain on South Africa, and encouraged American companies to withdraw, coincided in major banks like Chase Manhattan, Barclays, and Esso withdrawing investments
British sanctions were less forthcoming in the mid to late 1980s, Thatcher claimed it would cause more harm to black people than the government
The European Economic Community (EEC) imposed sanctions, costing South Africa millions and doubling black unemployment, (increased ANC membership)
Sporting sanctions were still in place, including ban to the Olympics from 1964 to 1992 and the Gleneagles Agreement (ban to 1987 and 1991 rugby world cups)
Sanctions take time to fully impact a country, as South Africa was still self-sufficient with available resources