It is normal practice for journalists to rummage around in the mind and soul of dead presidents to determine how and why they committed American blood, treasure and honor to unwinnable wars.

This, then, is a journey, inspired by Robert Caro’s massive third volume of his biography of Lyndon B. Johnson, a journey to discover why he and four other presidents paid so much in enmity to a nation we now consider a friend.

There is a terrible irony to war that yields more fruits in defeat than victory, which is deepened for me by the experience of meeting Gen. Giap in the early 1990s with a delegation of journalists in Hanoi.

Gen. Giap, victor in wars against the French and the United States, scholar, author, journalist, devotee of military histories — Napoleon and Sun Tzu are favorites. He appeared to us as a tiny, genial, white-haired grandfather.

His shrewdness surfaced when he was asked if he feared that the United States might use nuclear weapons against him. “No,” he said, “you didn’t use them against the Chinese.”

In 1995, he met with former Secretary of Defense Robert McNamara, who wanted to know what Giap’s forces had done in the Gulf of Tonkin that provided the pretext for Johnson’s escalation of the war.

“Nothing. Absolutely nothing,” the general told McNamara, it was a routine day. So, as we were later to discover in Iraq, the reason for significantly expanding hostilities was more imaginary than real.

Today, we visit our former enemy as tourists and trading partners. We are allied with Vietnam in the Southeast Asian Treaty Organization as barriers to contain China, which Vietnam has resented for centuries.

So how did the misbegotten war begin and develop the inertial force, a policy in motion that would continue in motion until combat troops were withdrawn in 1973 and the embassy was evacuated in panic two years later?

Who do we blame for the tragedy that took 20 years to unfold, and at what point along the way could we most easily and honorably have ceased hostilities?

Everyone has his pet villains: the right points the finger of blame at the news media and sissy politicians and has even invented quotes from Gen. Giap he never uttered to justify the claim that critical media “lost Vietnam.” The left has an easy explanation, “McNamara’s War.” The implication being McNamara had a Gatling gun for a brain and stone for a heart.

The left’s interpretation may be the most unfair. Anyone who read McNamara’s book In Retrospect: The Tragedy and Lessons of Vietnam, will see a heart burdened with guilt. I was his lunch partner once when he was writing the book, and seeing next to me a face so ravaged, I had no heart to raise the subject of Vietnam.

And I find it hard, impossible really, to blame Lyndon Johnson for Vietnam.

He took office when his staff and the nation were numbed by shock and blinded by personal and national loss, the murder of a popular president, John Kennedy.

The former president’s legislation was piled up against an obstreperous and immobile Congress. The legislative bog included civil rights legislation meant to relieve the contrary forces whose frustrations were erupting in the streets.

Grief and the families in its grip had to be respected and consoled, a steady and commanding presence had to be shown to a suddenly disoriented country and to adversaries abroad who wished us ill.

In Vietnam, President Diem had been assassinated three days earlier with the quiet approval of JFK, who was more than aware of his unpopularity. A new president was having difficulties in putting together his administration.

Party conventions and presidential elections were mere months away.

It was the worst of times for Lyndon Johnson.

It is true that President Johnson used an invented reason to escalate the war. It is true that he said he did not want to be the first president to lose a war. He had a dread of loss, personal humiliation.

But he wasn’t running a killing machine just to see Vietnamese and our soldiers die. There was no truth to the collegiate chant, “Hey, hey, LBJ; how many kids did you kill today.”

“I don’t know how to get out,” he told an aide, Jack Valenti. “I can’t just quit and run. And I don’t want to keep going on. So I have to get Ho (Premiere Ho Chi Minh) to the table. I’ve got to keep trying.” His goal was negotiation, with no hidden agenda.

Getting at the roots of this conflict, it began, innocently, with President Truman helping out wartime ally France in its struggle against Vietnamese nationalists who wanted independence from the occupying power.

The critical decision that could have avoided tragedy in Southeast Asia was the 1954 Geneva Accords following the French defeat at Dien Ben Phu, which called for removal of foreign troops and national elections.

The United States did not sign the treaty because Eisenhower’s Secretary of State John Foster Dulles had a better idea: nation building. We created an artificial state, South Vietnam, and installed Roman Catholic Diem to rule a mostly Buddhist population.

In his memoir, Eisenhower admitted that Ho Chi Minh would have won national elections by about 80 percent — the clearest possible evidence of the desires of the Vietnamese people.

Our futile commitment of blood, treasure and reputation was due to equal parts of innocence, ignorance and arrogance, the self-delusional belief that people whose culture we don’t know would rather be like us than be themselves.

H. Brandt Ayers is the publisher of The Star and chairman of Consolidated Publishing Co.