One thousand, one hundred, and fifty people wrote back. And of that group, he interviewed, alone or with his assistants, 172. Ryan’s daughter, Victoria Bida, told me that her father had once been away for eighteen months reporting, suggesting that to find the man, the reporter, you need look no further than his files. And to read the files—to deconstruct how the book was assembled, to connect names and stories in the book with questionnaires, interviews, letters, diaries, and regimental histories—is to feel yourself in the presence, so many years later, of a man compelled to learn everything.

Here, for instance, was the questionnaire from Lieutenant Donald Anderson of the 29th Infantry Division, who wrote about getting shot: “No pain, just stunned. Figured my brains were spilled all over my helmet.” Here was Ryan’s interview with General Maxwell Taylor, who commanded the 101st Airborne Division and who told him what it had been like parachuting into a dark field: “Lonesome as hell.” And here was the interview with Private Aloysius Damski, a Pole who had been forced to join the German 716th Infantry Division, who told of playing a card game called “scat” on the night before the invasion, then peeling away from his unit so that he could surrender to the British.

Then there was the material on Rommel, who committed suicide in October 1944 after he was implicated in a plot to murder Hitler. Ryan had the general’s diaries (nary an entry without comment about his dog) and an interview with his widow and son. But it was his adjutant, Captain Hellmuth Lang, who proved to be an interviewer’s dream. Lang recalled all the many telling details of the morning before the invasion, when Rommel, after a breakfast of tea and a slice of white bread with butter and honey, set out at precisely 6:47 a.m. in a black convertible Horch for his home in Herrlingen, where he would celebrate his wife’s birthday before continuing on for his meeting with Hitler. Frau Rommel later produced the birthday-gift shoes, long since resoled. And Lang, bless him, recalled the size: five and a half.

But Ryan was not only hunting for the small bits. As it happened, the Germans wanted it known that Rommel was not with his troops on D-Day because he was with the Fuhrer. Not so, Lang told him. He was at home—a discovery that was as thrilling as it was frustrating. Now he would have to rewrite the first chapter, and was already feeling overwhelmed by the task of culling, cataloguing, and deciding how best to use all the material he was gathering. “I do not know how I’m going to do this right now,” he wrote his wife Kathryn, a novelist who had also been his most valued aide.

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.”

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.