Joe Beyrle, who parachuted into Normandy on D-Day, had been terribly battered during seven months in German captivity. He managed to escape, on his third try, and fled through Polish farmland until he could hear the artillery fire of the eastern front, which sounded “like a welcome from God,” he told Mr. Taylor for his book, “The Simple Sounds of Freedom.”

HE hid in a hayloft, sucking on straw until it was soft enough to swallow, as the Red Army seized the farm, machine-gunned the German couple who lived there and fed the bodies to their pigs. He came out with his hands up, offering the Soviets a damp pack of Lucky Strikes.

When they offered him safe passage home, he said he would rather stay with the battalion. Why, they asked, dumbfounded. His answer was, “To fight the Nazis, fight them with you,” Mr. Taylor writes.

The war ended for him a few weeks later, when a German bomb blew him off a tank, and his commander  a woman he knew only as “the Major”  leaned over him and told him, Proshchai, tovarishch  Goodbye, comrade. Joe Beyrle returned to Muskegon, where everyone’s war stories were gradually papered over by ordinary life.

The feelings of fellowship between Moscow and Washington would not last long. By the 1950s, anti-Communist sentiment was so pervasive that, as John Beyrle put it, “If you were a prudent person, maybe you didn’t talk so much about the fact that you fought for the Red Army, even for a week.”

The American authorities discouraged Joe from contacting his Soviet war buddies and saw him as a “unique asset,” Mr. Taylor said. In the 1950s, the F.B.I. asked him to infiltrate a Communist cell in a labor union, and during the Vietnam War, when peace talks had stalled, the C.I.A. flew him into Laos to hand deliver a letter to a major in the Vietnamese Army.

It was his son, finally, who allowed Joe Beyrle to delve into his past. Steered toward Russian by one of his professors at Grand Valley State University in Grand Rapids, Mich., John Beyrle found work in Moscow as a guide for a United States government exhibit on farming techniques. He and his father began combing through archives, looking for a single survivor who might remember Joe Beyrle. The son joined the Foreign Service in 1983 and chipped away at the research during two tours in Moscow. The story began to draw attention.