Shortly after my latest book, Hue 1968, was published in June, my publisher received a note from a British journalist telling him I had gotten something important wrong.

The book tells the story of the bloodiest battle fought in the Vietnam War. The final chapter concerns one of the most famous photos from that war. Taken by John Olson, it shows a group of wounded Marines atop a Patton tank. The picture ran over two full inside pages of Life magazine in its March 8, 1968, issue, a haunting image from the worst fighting in the war. It did not identify any of the men on the tank.

For my book, I wanted to tell the story of the central figure in that photo, a young Marine who looks half-dead, stripped to the waist with a battlefield dressing around his chest and an IV line in his arm — he had clearly been shot in the center of his chest. He is laid out like a figure in a tragic Renaissance painting.

Who was he? Had he lived or died?

Olson told me that his name was Alvin Bert Grantham and that he had survived. He lives in Mobile, Ala. It turned out he had an excellent memory, and quite a story to tell. It forms the book's final chapter, which follows him from his wounding to his painful and prolonged recovery and brings his story up to the present. I thought it was the perfect way to end the book.

The note from the British journalist said with stinging finality that it was false. He had been researching a story about a photo taken of the same scene by the famous war photographer Don McCullin, and his work had determined that the wounded Marine was James Blaine, a private from Spokane, Wash., who had not survived. The Marines he interviewed told him Blaine had been shot fatally in the chest. He sent a photo of Blaine, and I had to admit, it looked a lot like the Marine in question.

My heart sank. Every reporter gets things wrong from time to time. For me, it is always accompanied by a stab of nausea. Erring on a key detail, even in a nearly 600-page book crammed with thousands of them, is enough to cast doubt on the whole book. How careful had the author been, after all, if he had gotten something that simple wrong?

I reviewed my reporting. Both the photographer and the subject were in agreement. Was it possible that Olson was wrong, and that Grantham had just gone along, inventing an elaborate tale?

Such things are not unheard of. There are a surprising number of men who lie about having been in battle. They wear false medals and march in parades and attend veterans' events, promoting themselves as heroes. There's a terrific book about it by B.G. Burkett and Glenna Whitley called Stolen Valor. I had written about it. Their reporting had  prompted a 2013 federal law by the same name that makes such impersonations a crime.

But Grantham was no self-promoter. It had been almost 50 years since the photo was taken, and he had never told his story. I had found him; he had not approached me. He was a modest Southern gentleman with a syrupy drawl who had never sought any recognition. And after nearly 40 years of reporting, I like to think I have at least some sense of when someone is telling me the truth. I told my publisher it was possible I'd been had, but I would be flabbergasted if it were so in this case.

Grantham responded with typical grace.

"Well, I don't want to rain on anyone's parade," he told me. "If someone else wants to claim to be that person, I don't mind. But like most people, I do recognize myself in a photograph."

I had never seen what he looked like at 18, which was how old he said he had been when wounded. He sent me a photo, and I was relieved to see that he had looked as much like the Marine in the photo as Blaine. He also forwarded a copy of the telegram the Marines had sent to his parents. It was chilling: "He sustained a gunshot wound to the right side of the chest. … His condition and prognosis were fair. … Your anxiety is realized." It confirmed the day of his wounding, Feb. 17, 1968.

Online, on the Vietnam Virtual Wall, you can look up the names of all 58,220 American fatalities in the war. Blaine is there. He was killed in Hue on Feb. 15, 1968. I called Olson to see if he knew which day he had taken the famous photo, and he said he did not. He had been in Hue over five days and had not marked the dates on his film rolls.

But he did know the names of others in the photo. I called one of them, Richard Hill, who lives in Fresno, Calif. He had been wounded in both legs in Hue, and he was the rearmost Marine in the tank photo.

"I have just two questions for you," I said, after explaining the reason for my call. "Is that you in the picture? And what day were you wounded?"

"It's me," he said. "I was wounded the evening of Feb. 16, and evacuated the following morning on that tank. That picture has been on my wall for 48 years. And that's A.B. Grantham in the front. We were both in Charlie Company. Blaine was not."

So Olson's picture was taken two days after Blaine died. Grantham was telling the truth. I contacted the British journalist, who graciously acknowledged he had been wrong.

His sources had not lied to him. Patton tanks were being used throughout the battle to transport wounded Marines to the rear. It is likely the men he  interviewed had placed Blaine on a Patton tank — perhaps the same one — two days earlier. They saw the picture, noted the resemblance to their fallen friend, and assumed it was him. On several Marine websites, the wounded Marine in the photo is still incorrectly identified as Blaine, and Grantham is not inclined to protest.

The past is tricky. Memories are not perfect, even when there's photographic evidence. No matter how hard we try, journalists sometimes get things wrong. But, thankfully, sometimes we're right.

Mark Bowden, a former Inquirer reporter, is the author of "Hue 1968."