And then, after he was done, he began doing the same thing all over again. Two more books followed: The Last Battle (1966), in which he recounted the fall of Berlin, and A Bridge Too Far (1974), the story of the Allies’ botched attempt to bring the war to a quick end in 1944. The latter is his most poignant and, at times, angry book; the first two, after all, ended in triumph. Like its predecessors, A Bridge Too Far tells of the personal courage of so many foot soldiers. But it also recounts the hubris of the commanders who sent those men into battle, an agonizing story of needless carnage that Ryan raced to finish as he was dying.

He had been diagnosed with prostate cancer at fifty, and despite a grim prognosis, had endured the rigors of his treatment and outlived by three years his doctors’ grave predictions. But by the spring of 1973, with A Bridge Too Far still not done, he wrote to an old friend, the San Francisco columnist Herb Caen, about the burdens of what had been his secret illness, and about the career he had crafted.

“I am three years late with it and the publishers are screaming,” he wrote. “The advances have been spent and we are trying to keep our heads above water with the hope that the book will be finished within the next four to six weeks.”

He had sold, he believed, between 25 and 35 million copies of The Longest Day and 400,000 hardcover copies of The Last Battle in the United States alone. Yet each book had cost him some $150,000 to research. “I have no less than 7,000 books on every aspect of World War II. My files contain some 16,000 different interviews with Germans, British, French, etc,” he wrote. “Then there is the chronology of each battle, 5x7 cards, detailing each movement by hour for the particular work I’m engaged in. You may think this is all a kind of madness, an obsession. I suppose it is.”

The books brought him fame and, even after deducting his research expenses, wealth. But as he confessed to Caen, he wished they’d also brought him a measure of professional recognition. “I’ve never seen myself as a writer but only as a journalist,” he wrote. Still, he hoped that his last book might bring him a Pulitzer. The Pulitzer board had not yet established a category for general nonfiction, and Ryan understood that he would find it hard to compete with academics for the big prize.

“So there’s probably little chance that I may be cited for a Pulitzer because so many of these bastards sit on the board,” he wrote, “but it would be nice to get one anyway.” (For the record, the 1975 prize in history went to Jefferson and His Time, Volumes 1-5, by Dumas Malone.)

Ryan was fifty-four when he died in November 1974, survived by his wife, son, and daughter. The material he had gathered in twenty years of reporting about the war went to Ohio University in Athens, where the dean of the College of Communications was an old friend. The collection’s curator, Doug McCabe, told me that even now, sixty-six years after D-Day, historians from around the world, as well as the children and grandchildren of men who fought that day, stop by to search through Ryan’s papers in the archive center of the library. It is, he said, the most heavily used collection in the center.

Meanwhile, The Longest Day was reissued in 1994 for the fiftieth anniversary of D-Day. It still sells—a fact that belies the glaring omission of Ryan’s work from so many anthologies of literary journalism, and also offers a powerful lesson for a trade trying to figure out what people will pay to read. There is nothing, it turns out, like a densely reported story propelled by the palpable sense of a reporter chasing his story.

Michael Shapiro is a contributing editor to CJR and teaches at Columbia's Graduate School of Journalism. His most recent book is Bottom of the Ninth: Branch Rickey, Casey Stengel, and the Daring Scheme to Save Baseball From Itself.