It was an early Monday morning when Akihiro Takahashi heard the faint drone of airplane propellers in the sky above him. He and his fellow junior high classmates had gathered on their school playground, pointing at the plane’s glistening silver body.

At precisely 8:15 a.m., a tremendous roar pierced Mr. Takahashi’s ears. Everything went black.

By his own admission, Mr. Takahashi should have died that day — Aug. 6, 1945 — when the Enola Gay, a B-29 Superfortress, dropped the “Little Boy” atomic bomb over his home town, Hiroshima, Japan.

Instead, Mr. Takahashi, who died Nov. 1 at age 80, spent his life speaking out against nuclear weapons and acting as Hiroshima’s ambassador for peace.

He visited Pope John Paul II and hugged the Dalai Lama. On a trip to Washington, he met Enola Gay pilot Paul Tibbets Jr. and held his hand.

As a witness to the Hiroshima attack, Mr. Takahashi retold his story hundreds, if not thousands, of times.

Born in Hiroshima in 1931, Mr. Takahashi had dreamed of joining the military and becoming a pilot. He was 14 when his hopes were dashed. He was about a mile from where the bomb exploded, and the blast knocked him 30 feet from where he stood.

His back, legs and arms were severely burned. His ears nearly melted off. Remembering his teachers’ bomb survival instructions, Mr. Takahashi rose to his feet and walked toward a nearby river, mainly to cool his body.

Along the way, he encountered a woman with her eyeball hanging by her cheek. He saw a man staggering by with shards of glass poking out of his chest.

“They looked like ghosts walking in procession,” he told the London Daily Telegraph in 2005.

He told Ohio’s Columbus Dispatch in 2005 that he passed “a baby wailing beside its mother who had burned to a charred lump.”

Once he reached the river, he waded in the water as corpses bobbed beside him.

As many as 85,000 people in the city died the second the bomb struck. Tens of thousands more died in the years after from injuries and radiation exposure. Of Mr. Takahashi’s 60 junior high classmates, 14 lived to adulthood.

Mr. Takahashi spent 18 months in hospitals for treatment of his burns. Some of his wounds were permanent. He could not bend one arm. The stiff fingers on his right hand made writing legibly a difficult task. He had chronic liver problems.

“Everyday I’m aware of the pain involved with living,” he once said. “In periods of despair, I sometimes wonder why I have continued to live for so long, with so much suffering.”

He often experienced discrimination as a “hibakusha,” the Japanese term for an atomic bomb survivor. He was turned down for several jobs before he started working for the Hiroshima government in the 1950s.

For many years, he hated Americans and called the atomic attack on Hiroshima, and a second one three days later on Nagasaki, an “experiment, and ordinary citizens were its guinea pigs.”

His attitude changed after a visit in 1978 to Hawaii, where he met relatives of the victims of the 1941 Japanese attack on Pearl Harbor.

“The deaths should not be wasted,” he told The Washington Post in 1980. “It is important to transcend hatred, to transcend the agony, to transcend the sorrow.”

Mr. Takahashi served four years as director of the Hiroshima Peace Memorial Museum, located almost directly underneath where the bomb exploded. He gave tours to visiting dignitaries, including Nobel Peace Prize recipients, and spoke to schoolchildren.

On a trip to Washington in 1980, Mr. Takahashi met Tibbets, an encounter that reportedly marked the first time an Enola Gay crew member had met a Hiroshima survivor.

Sitting on a park bench behind the Capitol, Mr. Takahashi and Tibbets talked about their experiences. They held hands.

“He expressed to Tibbets that he didn’t hold him personally responsible for such a terrible thing,” Greg Mitchell, co-author of the 1995 book “Hiroshima in America: Fifty Years of Denial,” said in an interview.

Mitchell said Mr. Takahashi recalled seeing a tear roll down Tibbets’s cheek during their conversation.

“I remember I met Tibbets and he told me, ‘Believe me, there was no tear in my eye. I feel sorry that they burned up down there, but it had to be done,’ ” Mitchell said.

Tibbets died in 2007. Mr. Takahashi’s death from a heart ailment was announced by the Hiroshima government.

“I tell myself that I’m a survivor of a terrible moment in history, and it is my belief that those of us who were saved should continue to talk of our experiences,” Mr. Takahashi said in 2002.

“We live to hand down the awful memories to future generations and represent the silent voices of those who died in misery and terror.”