Is there a more painful game of "What if?" that Americans could play than to wonder what the 1960s, and today, would look like if the U.S. had avoided military catastrophe in Vietnam?

The pivotal moment may have been in early 1965, when President Lyndon Johnson realized he was trapped in the early days of an escalating war the U.S. probably couldn't win. He knew the intensifying conflict would distract him from his prized agenda of creating "the Great Society" at home. But he also felt he had no choice but to proceed, because he'd won election in 1964 to a full term as president by promising to lick the North. "I feel like a jackass caught in a Texas hailstorm. I can't run, I can't hide and I can't make it stop," he's quoted as saying in Ken Burns' gripping new documentary series, "The Vietnam War."

Oh, the power of hindsight, and the tragedy of hubris. Both are powerfully demonstrated in the 10-part, 18-hour PBS documentary series that begins airing Sunday. Burns, co-director Lynn Novick and their team worked for 10 years to tell the story, interviewing dozens of witnesses, including combatants on both sides. It was worth the effort.

One of the most important points the series makes is that Johnson clearly understood the risk of beginning a major bombing campaign in the North and committing U.S. ground troops. If only he'd listened to his own taped phone conversations, which Burns uses to strong effect. Ever eavesdrop on someone making a terrible decision? That's what watching "The Vietnam War" feels like.

Burns, who with Novick recently visited the Chicago Tribune Editorial Board, said the purpose of their documentary wasn't to pass judgment or play the "What if?" parlor game, but to put the passage of time to his advantage as a documentary-maker. After 40 years, the consequences are better understood, and once-hidden details have been uncovered and studied.

The Vietnam era was polarizing and it was agonizing, spawning political upheaval and a cultural revolution in the U.S. Burns believes the war unleashed an era of partisanship the nation reckons with today. In all, the Vietnam War provides enduring lessons, but also puzzles. How is it that four decades after the morass of Vietnam, America is 16 years into another long-running, problematic war, this one in Afghanistan? What does that say about the significance of studying history?

FROM AN EDITORIAL IN THE CHICAGO TRIBUNE