The North Vietnamese didn’t know what to make of their prisoner.

Hours upon hours of first abusing him, then pumping him for military information, had produced nothing but a nasty nickname for the young American sailor. To their thinking, he was simply dumb as a rock.

Which was exactly what Petty Officer 2nd Class Doug Hegdahl wanted them to think. Because he was anything but stupid. Indeed, he cleverly used what his captors believed to be idiocy to brilliantly outwit them.

The road that ultimately led Hegdahl to Hanoi started nearly 7,700 miles away in his hometown of Clark, S.D. (Population 1,148 in 2020.) The chance to see the world appealed to the innocent small-town boy who had seldom been far from home. So he signed up for a hitch in the U.S. Navy in 1966—just as the Vietnam War was ramping into overdrive.

He found himself onboard the USS Canberra in the Gulf of Tonkin a few months later. Early on April 6, 1967, as the cruiser was blasting away at targets on the North Vietnamese coast, Hegdahl stepped onto the deck, either for some fresh air or for a quick smoke. That was a huge no-no when the big guns were firing because a sailor could be knocked overboard. Which was exactly what happened.

He swam for a few hours until being picked up by local fishermen, who promptly handed him over to the North Vietnamese military.

The goons who interrogated him didn’t buy his tale of being blown into the water. They suspected he was a commando on a secret mission. Hegdahl realized he was in seriously hot water and had to act fast.

So, he decided to play dumb. Really, really dumb. Talking in an exaggerated country accent, he claimed to be a simple farmboy. They beat him for a few days, but he consistently stuck with the bumpkin act until the North Vietnamese came to believe him. When they tried to get him to sign a propaganda statement, he readily agreed—except for the unfortunate fact that he couldn’t read or write, he said. It rang true to his captors since most Vietnamese farmers were illiterate.

They brought in a tutor to teach him basic reading and writing. The teacher quit in frustration a few weeks later, saying the prisoner was just too dumb to learn. The North Vietnamese finally threw up their hands in frustration. That was when they started calling him “The Incredibly Stupid One.”

What they didn’t know was Hegdahl was far from stupid. Convinced he was useless, he was allowed to roam around at will inside the prison compound. Yet during those solitary walks, he quietly poured dirt into the gas tanks of military vehicles, disabling five trucks.

With the help of an American Air Force officer, he memorized the names, capture dates, and other important details about more than 250 U.S. POWs. (He committed all that extensive data to memory by singing it to the tune of “Old MacDonald Had a Farm.”)

When he was transferred to the infamous Hanoi Hilton prison, Hegdahl quickly learned his fellow prisoners had vowed to reject an early release if it became available. They would all leave together or not at all.

Two agonizingly long years later, the North Vietnamese decided to return three POWs as a propaganda measure. Because he was dismissed as such a low-value captive, Hegdahl was selected to be one of them. He initially refused to go. But his cellmate and Navy superior ordered him to accept the offer because of the wealth of critical information he had memorized.

And so Hegdalh was turned over on August 5, 1969, and immediately provided a library of important details to U.S. military officials.

But he had a score to settle with the brutes who were still holding his comrades in Hanoi.

At the secret Paris Peace Talks in early 1970, North Vietnam’s negotiators denied abusing POWs. So Hegdahl was sent to the meeting, where he looked his former captors in the eye, called out their lies, and helped pressure them into eventually agreeing to release the American prisoners. It took a while, but on February 12, 1973, the first POWs were let go. By late March, all 591 had been set free.

And “The Incredibly Stupid One” had played a big part in making it happen.

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