23 March 1952
The Defiance Campaign was planned in the 1950s in response to the enactment of numerous apartheid laws by the South African government. During the African National Congress (ANC) Annual Conference in December 1952 it was decided, "to embark on mass national action, based on non-cooperation, against certain specified unjust and racially discriminatory laws of the Union Government, unless these laws were repealed before March 1, 1952". Organisations like the Congress of Democrats and the South African Indian Congress (SAIC) joined the campaign. More than 8 500 people were imprisoned for refusing to obey apartheid laws and the campaign attracted thousands of people to political activism. Conservative Chief Cyprian Zulu regarded this opposition to the government as dangerous and warned his people not to get involved. Read more about the Defiance Campaign.
References

SAHO, Defiance Campaign 1952, from South African History Online, [online], Avaialable at www.sahistory.org.za [Accessed: 20 March 2013]