History and pop culture have trained us to celebrate battlefield heroics and other forms of physical courage. Those actions are undeniably admirable, and in the past decade many Vietnam veterans have received overdue valor medals or had existing awards upgraded.

Heroism also comes in other forms.

Doug Hegdahl, the subject of Marc Leepson’s “The Unlikely War Hero: A Vietnam War POW’s Story of Courage and Resilience in the Hanoi Hilton,” engaged in quieter, more cerebral acts, but he was a hero of the Vietnam War just the same.

The average reader probably hasn’t heard of Hegdahl. It’s not because his story isn’t fascinating. In short, a young man from tiny Clark, S.D., committed some of the most courageous noncombat actions of the war.

In the early hours of April 6, 1967, Hegdahl fell off the guided missile cruiser USS Canberra as it fired its 5- and 8-inch guns from the Gulf of Tonkin on North Vietnamese positions inland. The member of the deck crew went up to watch the guns fire, but he couldn’t remember how he ended up in the water. Nobody saw the 20-year-old seaman apprentice go overboard. His shipmates did not know for hours that he was missing. His captain did not turn the warship around to look for him.

After treading water for hours, the exhausted Hegdahl was pulled from the South China Sea by fishermen. His rescue took a quick turn, however, when the fishermen turned the young sailor over to the North Vietnamese.

He ultimately ended up in the Hoa Lo prison camp. That name also might be unfamiliar, but most probably know the name mockingly given to it by American prisoners of war: the Hanoi Hilton.

Hegdahl was subjected to intense interrogation, and to torture when his answers failed to satisfy his captors. He quickly devised a strategy to confuse his interrogators and, hopefully, escape severe punishment.

“I had probably the most embarrassing capture in the entire Vietnam War,” Hegdahl said during a 1997 interview cited in the book. “I found that my defense posture was just to play dumb. Let’s face it, when you fall off your boat, you have a lot to work with.”

It worked. Although prison officials initially thought that Hegdahl was a spy (a suspicion shared by even some of his compatriots, among other theories), he quickly dissuaded them of the notion. He convinced them that he knew little valuable information, or little at all. It worked so well that he came to be known as “The Incredibly Stupid One” by his captors.

Hegdahl was anything but stupid.

The bumpkin act caused the North Vietnamese to pay Hegdahl little mind. He was the youngest and lowest-ranking man in the camp, which was full of experienced pilots and navigators. Since prison officials thought he was a simpleton, Hegdahl often was allowed unsupervised time to sweep the yard. He spent some of that time sabotaging camp vehicles. Once he even wandered out into the street, helping him to pinpoint the camp’s location.

A few months into his captivity, Hegdahl was placed in a cell with a senior Naval officer, Lt. Cmdr. Richard Stratton, who became Hegdahl’s closest friend during his captivity and for decades after the war. Stratton recognized Hegdahl’s smarts, and the need to use them.

Hegdahl’s knack for memorization was a tremendous asset, and one that dovetailed with POW efforts underway at the Hanoi Hilton. Picking up on a practice already in place, he memorized the names of 254 prisoners. All the while, he played his subterfuge to the hilt. His captors treated him like the village idiot, while Hegdahl foiled their attempts to use him for propaganda purposes and banked vital information.

The North Vietnamese released Hegdahl in August 1969, without a clue as to the storehouse of valuable intel locked in his mind. Information that gave hope to families of missing and imprisoned servicemen. Information that helped to change the conditions in the Hanoi Hilton.

Said Roger Shields, who served as Deputy Assistant Secretary for POW/MIA Affairs from 1971 to 1977: Hegdahl “saved many, many lives. I don’t think there’s any doubt about it.”

“The North Vietnamese released Hegdahl in August 1969, without a clue as to the storehouse of valuable intel locked in his mind. Information that gave hope to families of missing and imprisoned servicemen. Information that helped to change the conditions in the Hanoi Hilton.”

Leepson, a Vietnam veteran, historian and the longtime senior writer, arts editor and columnist for The VVA Veteran (the magazine of Vietnam Veterans of America), has a firm handle on the subject. Utilizing archival research, personal interviews and his own experiences in the war, Leepson has written a thoroughly engaging biography – the first of its kind – about one of the unsung heroes of Vietnam.

“The Unlikely War Hero” was the No. 1 bestselling Vietnam history book on Amazon just prior to its mid-December release, and it is already into its third printing. It’s little wonder; Hegdahl’s incredible story adds a compelling facet to the canon of Vietnam literature.

Leepson provides valuable context regarding life in the camp, such as how prisoners forbidden to communicate with one another did just that. He sketches the politics of the era - without bogging down the story - and the external forces, within the U.S. government and the anti-war movement, which affected life on the inside for the POWs.

Hegdahl, who has not spoken publicly about his captivity since around 2000, chose not to participate in the book, citing a desire to remain a private person. That’s a shame, if only because Leepson likely could have drawn more insight or a new perspective out of him. But the book does not suffer for his absence. It is meticulously researched, and it makes expert use of interviews Hegdahl did in his first several years after returning to the U.S.

Leepson, who has written about a wide range of historical topics, uses varied sources to buttress the narrative but never weighs it down with footnotes or tangents. The writing is clean, generally conversational, and absent of excessive acronyms or jargon that might turn off many readers.

Hegdahl didn’t face overwhelming odds on the battlefield. He didn’t jump on a grenade to save his fellow servicemen. But what he did as a POW and as an advocate for fellow prisoners was no less heroic. It is a compelling story, told by a skilled storyteller. At the end of the book, Leepson makes a case for Hegdahl to receive the Navy and Marine Corps Medal (although Hegdahl has resisted such efforts). By the end of “The Unlikely War Hero,” you’ll wonder why it didn’t happen decades ago.