21 October 1973
In 1973 massive strikes occurred throughout South Africa, culminating in September 1973 at the Western Deep Levels mine at Carletonville, when 12 striking miners were killed as police fired on a crowd. Shortly afterwards it was reported that the South African government has banned twenty leaders of Black organisations, including the South African Students' Organisation (SASO), the Black People's Convention (BPC), the Black Community Programme (BCP), the Black Allied Workers' Union (BAWU) and the Black Workers' Project. Members of the South African Black Scholars' Association (SABSA) were interrogated security police.  
References

Kalley, J.A.; Schoeman, E. & Andor, L.E. (eds) (1999). Southern African Political History: a chronology of key political events from independence to mid-1997, Westport: Greenwood.|Reader's Digest. (1988). Illustrated History of South Africa: the real story, New York: Reader's Digest Association, p. 454.