Complex sentence: Vorster retired as Prime Minister in 1978, after twelve years in office, and was succeeded by P.W. Botha, a hardliner who nevertheless began the first reforms to moderate the apartheid system.
Split into simpler sentences: Vorster retired as Prime Minister in 1978, after twelve years in office. He was succeeded by P.W. Botha, a hardliner who nevertheless began the first reforms to moderate the apartheid system.