Mr. Mandela, approaching 40 and the father of three, declared on their first date that he would marry her. Soon he separated from his first wife, Evelyn Ntoko Mase, a nurse, to marry Ms. Madikizela-Mandela on June 14, 1958.

Ms. Madikizela-Mandela was thrust into the limelight in 1964 when her husband was sentenced to life in prison on charges of treason. She was officially “banned” under draconian restrictions intended to make her a nonperson, unable to work, socialize, move freely or be quoted in the South African news media, even as she raised their two daughters, Zenani and Zindziswa.

In a crackdown in May 1969, five years after her husband was sent to prison, she was arrested and held for 17 months, 13 in solitary confinement. She was beaten and tortured. The experience, she wrote, was “what changed me, what brutalized me so much that I knew what it is to hate.”

After blacks rioted in the segregated Johannesburg township of Soweto in 1976, Ms. Madikizela-Mandela was again imprisoned without trial, this time for five months. She was then banished to a bleak township outside the profoundly conservative white town of Brandfort, in the Orange Free State.

“I am a living symbol of whatever is happening in the country,” she wrote in “Part of My Soul Went With Him,” a memoir published in 1984 and printed around the world. “I am a living symbol of the white man’s fear. I never realized how deeply embedded this fear is until I came to Brandfort.”

Contrary to the authorities’ intentions, her cramped home became a place of pilgrimage for diplomats and prominent sympathizers, as well as foreign journalists seeking interviews.