He had said 6:15 p.m., so my mother and I had left her house in plenty of time. But there had been an accident on East Main Street, and we were stuck in traffic, and there was no way we were going to be at Fisherman’s Wharf by 6:15.

“I guarantee you one thing,” I said to my mother. “When the clock strikes 6:15, he’ll be sitting at the table.”

Paul Tibbets. He had asked my mom and me to join him for dinner–this was on a warm Wednesday night this summer, in Columbus, Ohio, where Tibbets lives, where I grew up, where my dad had lived and died–and if there is anything I have learned about Tibbets, it is that he is never late. Ever.

Certainly not on that 6th day of August 55 years ago, when at the request of his country he did what no person in the history of mankind had ever been asked to do–when he flew the world’s first atomic bomb over an enemy nation. In a plane he named for his mother, Enola Gay, he and his crew dropped the bomb on Hiroshima, and at long last World War II was about to end.

On that summer day in 1945, Tibbets had had no satellite navigation to guide his B-29 from the American air base on Tinian Island in the Pacific to Hiroshima; no computers to keep the plane on course. Tibbets and his crew made the flight by checking their watches, and the stars above. It was a six-hour, nearly 2,000-mile trip. The plan had called for the atomic bomb to be released from the Enola Gay at 8:15 a.m. Japan time. Tibbets flew the plane over the T-shaped bridge in Hiroshima at 8:15 a.m. plus seventeen seconds. (“We were off,” he would tell me. “We weren’t perfect.”)

So now, in the summer of 2000, I knew he’d be waiting for us. Fisherman’s Wharf is near no majestic body of water, unless you count Columbus’ Alum Creek; it’s just a nice, unpretentious place on Main Street, and my mom and I walked in, and Tibbets rose to greet us.

He’s 85. Had any of the local television weathermen in Columbus been in the restaurant, or any of the Ohio State University football or basketball stars, they would have caused quite a stir. Not Tibbets. As always, even in his hometown, he went unrecognized.

Which seems just fine with him. Because “Duty” tells the story of how Tibbets helped me understand my father’s life–how Tibbets was able to tell me things about why my dad’s service with an infantry unit in World War II was so important to him, why it was the central event of my father’s time on Earth. My mother, and her last months with my dad, are a constant and deeply emotional part of “Duty” as well. When Tibbets heard I would be back in Columbus to see my mom, he said he thought it would be nice if we all got together. So here we were, in a land at peace, with August 6 approaching once more.

I asked if he paused to commemorate the day each year.

“The answer is, I did at first,” he said. “Just privately, to myself. And I would look at the newspapers each August 6, to see if there was any mention made. Some years, not a word was in there.”

Tibbets looked off, as if trying to see some invisible calendar. “In a personal way, it’s getting away from me, that day. It was a long time ago. It has lost no significance. I think I did it right–what I was asked to do that day, I did right. But when August 6 comes along every year, I don’t do anything special on that day.”

Many times he has told me that he has never lost a night’s sleep over the dropping of the bomb. Even with the unfathomable death and carnage on the ground below, he believed then–and believes now–that so many more lives, American and Japanese, were saved because he flew the mission and the war ended and the killing stopped. Oftentimes, in Tibbets’ presence, I would see men and women in their seventies and eighties come up to him (once they figured out who he was) with tears in their eyes, to thank him for letting them live full lives. The men had been young American soldiers on their way to a land invasion of Japan. Because of what Tibbets did, they came home instead, and raised their families. They cry now, when they meet him.

“As the years go by,” I asked him, “do you still ask yourself, ‘Why me?’”–why he, of all the men in the U.S, military in World War II, had been selected to put together this unit, and to fly the bomb to Japan?

“I don’t ask questions like that,” he said. “I know what I did–and I did it like I’d do it again under the same circumstances.”

“What about your memories of the day?” I said. We had talked about the flight so many times in the most precise detail. “The seat slapped me on the ass,” Tibbets had told me, when he had explained the effect inside the plane at the moment the five-ton bomb had been released. And when, after the bomb exploded, he had looked down at Hiroshima, “I looked at that city–and there was no city, there was nothing but the fringes of where the city used to be….”

Now I was asking him if the memories stayed the same over time–if, 55 years later, they were becoming hazy, or if they were still as vivid.

“I don’t think it fades,” he said. “It gets condensed. I don’t think so much anymore about all the steps we took getting ready for the flight. But when we got to Hiroshima…when we began the final part of the mission, the part they had sent us there for…that is still as clear to me as the day we flew there. Every second of it.”

And if he had failed? If the mission had not succeeded, and the bomb had not been dropped, and World War II had continued?

“The damn thing wasn’t going to fail,” he said to me. “I was taking the plane there–and I wasn’t going to let it fail.”

But what if the scientists had declared the bomb not ready–or if President Truman had decided not to give the order? What if the war had been allowed to go on, and the battlefield deaths had kept mounting?

“If we hadn’t flown our mission, I think mankind would have lost a lot,” Tibbets said.

He knows that there are some who, all this time later, disagree with him. He knows that there are some who continue to be highly critical of what he was asked to do on that August day. His response to that is as direct as Tibbets himself: “Those people never had their balls on that cold, hard anvil. They can say anything they want.”

Not that he used that language tonight; my mom was at the table. Fifty-five summers later, an 85-year-old man in an Ohio restaurant, Tibbets told my mother how pleased he was that she could join us for dinner. We talked about a lot of things, and at one point, speaking of that long-ago August, Tibbets said, “What they asked me to do was something that had not been done before. I think it was one of the most important days in the life of the world.”

“Was it the most important day in your life?” I asked.

“My life’s not over yet,” he said.