11 July 1963
South African police raided the African National Congress (ANC) underground headquarters, the Liliesleaf Farm in Rivonia, just outside Johannesburg. Apparently it was decided that the 11th July 1963 would be the last time they would meet at the farm.Virtually the entire leadership of Umkhonto we Sizwe(MK), armed wing of the ANC, were arrested on this day. This moment came as a terrible titanic dream in the history of the ANC. Amongst those arrested were;  Walter Sisulu, Govan Mbeki, Raymond Mhlaba, Ahmed Kathrada, Lionel Bernstein and Bob Hepple. Nelson Mandela, the commander-in-chief of MK, was not arrested at the time as he was serving a five-year prison sentence for leaving the country illegally in 1962. The farm was privately owned by Arthur Goldreich, but bought with funds from the Communist Party of South Africa (CPSA).  At the farm police found documents relating to the manufacture of explosives, Mandela's diary of his African tour and copies of a draft memorandum, 'Operation Mayibuye'. It outlined a possible strategy of guerrilla war fare.  The six men had been studying the document when police arrived. More arrests followed shortly after this incident, including Arthur Goldreich, Andrew Mlangeni, James Kantor, Dennis Goldberg, Harold Wolpe and Elias Motsoaledi. Goldreich and Wolpe later managed to escape from prison. Mandela and his co-accused were sentenced to life imprisonment in the Rivonia trial that ended in June 1964.
References

Liliesleaf Farm, ‘A Brief history of South Africa’s Socio-Political Context: 1948-1964’, [online], available at www.liliesleaf|Muller, C.F.J. (ed)(1981). Five Hundred years: a history of South Africa; 3rd rev. ed., Pretoria: Academica.|Reader's Digest. (1988). Illustrated History of South Africa: the real story, New York: Reader's Digest Association, p. 412.|Rust Bernstein, ‘Lionel "Rusty" Bernstein Profile’, [online], available at www.rusty-bernstein.com(Accessed: 01 Jun. 12)