Mandela abandoned his nonviolent stance and began advocating acts of sabotage against the South African regime. In 1962 he was jailed and sentenced to five years in prison.

In 1963 the imprisoned Mandela and several other men were tried for sabotage, treason, and violent conspiracy in the celebrated Rivonia Trial, named after a fashionable suburb of Johannesburg where raiding police had discovered quantities of arms and equipment at the headquarters of the underground Umkhonto We Sizwe (“Spear of the Nation,” the ANC's military wing). Mandela had been a founder of the organization and admitted the truth of some of the charges that were made against him. On June 12, 1964, he was sentenced to life imprisonment.