ACCRA, Ghana — FOR years, it seemed as though only one photograph of Nelson Mandela existed. It showed him with bushy hair, plump cheeks, and a look of serious determination. But it was a black-and-white shot, so grainy it looked ancient — a visual documentation of an era and an individual whose time had long passed.

In the early 1960s, fed up with the systematic oppression and inhumane treatment of indigenous Africans, Mandela successfully proposed a plan of violent tactics and guerrilla warfare, essentially forming the military wing of the African National Congress. Within a few years, this martial division, aptly named Umkhonto we Sizwe or Spear of the Nation, was discovered and its leadership detained. In 1964 Mandela was found guilty of sabotage, and ordered to serve a life sentence.

During his trial, in lieu of testimony, he delivered a speech from the dock. “I have cherished the ideal of a democratic and free society in which all persons live together in harmony and with equal opportunities,” he said. “It is an ideal which I hope to live for and to achieve. But if need be, it is an ideal for which I am prepared to die.”

I was 5 years old when Nelson Mandela became prisoner number 46664, and was banished to spend the remainder of his years on Robben Island, five square miles of land floating just north of Cape Town. Robben Island had been the site of a colony for lepers, a lunatic asylum and a series of prisons. It was a place of exile, punishment and isolation, a place where people were sent and then forgotten....