Like Julian Assange, Nelson Mandela was a fighter for Freedom, Truth and Justice (no more, no less). Mandela was outspoken and held fast to his principles, just like Julian, and for that he was put in prison for many years by the established, just like Julian. Unfortunately, it is very common that fighters for freedom and justice are silenced and locked away or worse by established orders in general.
However, growing domestic and international pressure and fears of racial civil war led President F. W. de Klerk to release him in 1990. Mandela and de Klerk led efforts to negotiate an end to apartheid, which resulted in the 1994 multiracial general election in which Mandela led the ANC to victory and became president. (Wikipedia)