What were the strategies of the South African government to maintain Apartheid policies?
The Apartheid (Afrikaans for "separateness") system of racial laws adopted as national policy starting in 1948 (same year Truman desegregated the US Army). The white government of the country did the simple math and decided they would need apartheid to maintain control of the native population, which was much larger than the population of British and Dutch descendants.
As the disparity between the two populations grew, as civil rights movements in the US and elsewhere progressed, and while organizations such as the African National Congress and Inkatha Freedom Party became a direct threat to their hold on power, Apartheid policies became more strict, and enforcement of them more aggressive. So a good way to put this is that Apartheid strategy evolved in direct proportion to the size of the native South African population and the threat the white government believed them to be.