Nelson Mandela was imprisoned because he opposed South Africa's apartheid system, a regime that enforced racial segregation and oppression against non- white South Africans. Initially, Mandela engaged in peaceful protests and civil disobedience against apartheid laws. However, as the government responded with violence and repression, Mandela concluded that armed struggle was necessary and became a leader of Umkhonto we Sizwe ("Spear of the Nation"), the armed wing of the African National Congress (ANC). He was arrested in 1962 for leaving the country illegally and inciting a strike and later sentenced to life imprisonment in 1964 after the Rivonia Trial for sabotage and conspiring to overthrow the state. He spent 27 years in prison, mostly under harsh conditions, refusing to abandon his fight for racial equality and justice. Mandela was finally released in 1990 and played a key role in ending apartheid and becoming South Africa’s first democratically elected black president.