After 1948, the National Party bonded itself to the Apartheid ideology. The plan was to fabricate a permanent white political majority by purging the voter's role of all Blacks, and by creating "Homelands" for all Black people where political provision could be made for them leading up to self-government, an option eventually exercised by most of the larger homelands.
In 1955 the resistance movements drew up a document that ironically became almost a blueprint for later negotiations to form the new South Africa. This document known as the "Freedom Charter; was wiped off the table by the National Party, and organised resistance intensified.
After 69 people were killed in a demonstration against the "Pass Laws" at Sharpeville in 1960, political pressures forced South Africa out of the Commonwealth and into becoming a republic under the leadership of Hendrik Verwoerd.
Soon afterwards, the ANC founded their armed wing, "Umkhonto we Sizwe" (Spear of the Nation), and embarked on a campaign of limited sabotage that resulted in the arrest of Nelson Mandela and other leaders. In 1964 Mandela, together with others, was convicted of high treason, sentenced to life imprisonment and sent to Robben Island.
After the assassination of Verwoerd in 1966, his successors John Vorster and P.W. Botha instituted some measures to soften apartheid, while toughening internal security. But in the 1970's the balance of power began to change. Worker opposition, international sanctions, and the growing interdependence of Black and White in a modern and urbanising economy, combined to make the apartheid system increasingly untenable.