It was April 1980, and I was among the crowd serenaded by Bob Marley and the Wailers when Britain’s Union flag was lowered to be replaced by a new banner. A whiff of tear gas floated over a wall at the Rufaro soccer stadium in Harare, the capital of the nascent state of Zimbabwe.

Prince Charles was on hand to formally give up control of his country’s last African colony. A slender, bespectacled man who would become one of Africa’s most notorious despots was about to secure a prize he had long coveted.

At midnight, Zimbabwe — the former Rhodesia — became Africa’s newest independent state, and Robert Mugabe, the clear winner of internationally supervised elections just weeks earlier, was its first prime minister.

It was a crowning moment. A seven-year war had ended in victory for the nationalist guerrillas, and Mr. Mugabe was about to start on a trajectory that led from democratic roots to an inexorable gathering of power unto himself.