One day [Marine Theodore Wallace] saw an officer casually aim his rifle and try to shoot a Vietnamese boy in the distance.

“Sir, what are you doing?” he’d asked.

“He’s probably supplying the [North Vietnamese Army],” the officer said. “What’s he doing out here anyway?”

“It’s his country!” said Wallace.

— Mark Bowden, “Hue 1968: A Turning Point of the American War in Vietnam”

WASHINGTON — As Vietnam’s 1968 Tet holiday approached, Gen. William Westmoreland, commander of U.S. forces there, cabled the Joint Chiefs in Washington that he had a plan. He would serenade, perhaps into dissolution, the communist forces that he was certain would concentrate on attacking U.S. forces based at Khe Sanh near the demilitarized zone:

“The Vietnamese youth is quite sentimentally disposed toward his family, and Tet is a traditional time for intimate family gatherings. The Vietnamese PSY War [Psychological Warfare] people have recently written a highly sentimental Tet song which is recorded. The Vietnamese say it is a tear-jerker to the extent that they do not want it played to their troops during Tet for fear their desertion rate will skyrocket. This is one of the records we will play to the North Vietnamese soldiers in the Khe Sanh-Con Thien areas during Tet.”

This surreal nugget is from Mark Bowden’s magnificent and meticulous history, which tells, with excruciating detail, a story that is both inspiring and infuriating. His subtitle is an understatement. As the epicenter of North Vietnam’s Tet offensive throughout South Vietnam, the swift capture of Hue, the country’s third-largest city, by communist forces — and of the 24 days of ferocious fighting that expelled them — became a hinge of American history. A month later, President Lyndon Johnson announced he would not seek re-election in an America where opposition to the war and trust in the government were moving inversely.

After the battle’s first day, Jan. 31, Westmoreland told Washington that the enemy had about 500 men in Hue’s Citadel. “He was,” Bowden writes, “off by a factor of 20.” So it went with U.S. intelligence. A few months earlier, Walt Rostow, Johnson’s national security adviser, had told a Hue-bound reporter on “deep background” that the war was essentially already won because a crop called “IR8 rice” was going to stymie the communists’ revolution with a green revolution. Rostow’s theory was slain by this fact: The Vietnamese disliked the taste of IR8 rice.

The communists arriving in Hue immediately began advancing the revolution by purging “enemies of the people” in what quickly became an orgy of violent score-settling. While Westmoreland remained fixated on Khe Sanh — “Never,” writes Bowden, “had a general so effectively willed away the facts” — a secret U.S. planning group met in Okinawa the day after the offensive began to consider a plan, code-named Fractured Jaw, involving tactical nuclear weapons. Westmoreland said these were not needed “in the present situation.”

Bowden’s interviews, almost half a century on, with those who fought, on both sides, have produced unexampled descriptions of small-unit combat. The communists’ many months of large-scale infiltration and preparation were matched by their military skills. “To a man,” Bowden writes, “the American veterans I interviewed told me they had faced a disciplined, highly motivated, skilled and determined enemy. To characterize them otherwise is to diminish the accomplishment of those who drove them out of Hue.” In June 1968, Westmoreland was relieved of his command.

What Bowden calls “one of the great shots in the annals of combat photography” is of a U.S. tank in Hue draped with dead and wounded Marines. None were identified. Until, more than four decades later, Bowden found that the 18-year-old with a hole in his chest, who looked “dead, or nearly so,” was Alvin Bert Grantham from Mobile, Alabama, whose story Bowden tells.

During house-to-house fighting, Marine Eden Jimenez was clearing rooms — tossing in grenades, then spraying the room with bullets — in one of which he found a tall wardrobe that he had riddled. In it was a mortally wounded woman holding a rifle and a baby. Bowden writes: “When he was an old man, living in Odessa, Texas, he still wondered almost every day about that woman and child. … Who was she? How would he have felt if he had killed the baby, too?”

Hue, like the war that pivoted there, continues to haunt some elderly men who live among us. And the war’s legacy lives in Americans’ diminished trust in government. Since 1968, trust has not risen to pre-Vietnam levels.

George Will’s email address is georgewill@washpost.com.