Throughout a long career in politics, presumptive Republican presidential nominee Sen. John McCain has had his foreign policy shaped by his and the United States’ experience in the Vietnam War.

But that shaping has been very dynamic  not beholden to any one particular lesson of the conflict, but rather taking each political situation presented to him and viewing it through the lens of Vietnam, often with mixed results.

The most potent example of this today is also one of the biggest campaign issues  McCain’s support for the Iraq war. The war, many feel, violates some of the primary lessons of Vietnam that were thought to be solidified in the Powell Doctrine of former George W. Bush secretary of state Gen. Colin Powell (Ret.), who along with McCain was informed by his service in Vietnam.

The Powell Doctrine sets out requirements for US engagement in a military conflict. Included in the criteria are US public support, clear objectives, and the use of overwhelming military force.

But just as critics use Vietnam to challenge the folly of continued occupation, McCain uses it to defend the US presence there  citing a Vietnam-era criticism of the US that it had "lost the will to fight."

McCain’s own military service during and after the Vietnam War was fraught with the sort of drama usually reserved for war films. A naval aviator, McCain’s plane was shot down over Hanoi, the capital of North Vietnam. McCain was then taken prisoner and tortured for five years  notably refusing to be released early, out of order of capture, because of his father’s position in the Navy.

Upon his release from captivity, McCain returned to the US as a war hero, and used the platform afforded him to support President Richard Nixon’s escalation of the conflict and, notably, his support for the "Domino Theory"  that if South Vietnam fell to communists, a "red fever" would spread across Southeast Asia and strengthen global communism and its alleged goal of violent and forceful world domination.

"I don’t hold him accountable for anything he said right after returning from Vietnam," author, blogger and political consultant Cliff Schecter told IPS, citing the stress and trauma of the long captivity.

But while McCain moved away from many of his originally stated lessons on Vietnam as he went into politics, he has since returned to many of them as he has grown closer to the neoconservative movement  rehashing the old arguments to warn about the dangers of leaving Iraq even as those ideas proved to be false alarms in the case of Vietnam.

"He was a little attached to Vietnam at first, but then he learned his lesson about Vietnam," said Schecter, calling McCain’s worldview at the time something akin to Powell’s. "He entered public life  in 1982 when he won his congressional seat  as a complete isolationist."

One of the first indications of McCain’s "maverick" status was when he broke with party ranks in 1983 to oppose President Ronald Reagan’s plan to keep troops in Lebanon. The vote cast was on the losing side, but troops would nevertheless be pulled when US barracks there were bombed.

Similarly, McCain opposed the use of force in Somalia and Haiti in the 1990s.

"Just like that, in 1997 and 1998 he did a complete 180 when he started hanging out with the neoconservative crowd," said Schecter, whose book on the Arizona senator, an unsympathetic profile called The Real McCain, was recently released. "McCain has broken with his bothers in arms to join this group of armchair warriors who theorize on blackboards and computers and have never been actually been to war."

The allegiance with that crowd was codified in 2000 when neoconservative Randy Scheunemann was added to McCain’s 2000 presidential bid as an advisor. For his 2008 run, McCain has taken on Scheunemann as his foreign policy chief.

At an event at the Washington think-tank the Brookings Institution earlier this month, Scheunemann spoke of another of McCain’s fears about a US defeat in Iraq  a weakening of US military forces. Again, McCain’s contention was based on the Vietnam experience of returning to active duty in command of a squadron rife with recruiting issues and planes grounded due to disrepair.

"[McCain] served in the military in the aftermath of defeat and saw firsthand how difficult it was to recruit and retain personnel to keep aircraft flying and so on," said Scheunemann.

But Shecter complains that McCain and Scheunemann have it backwards; it is the Iraq war itself that has weakened US military forces rather than the specter of defeat.

"By any real measure, the military is so unprepared right now because of the war that John McCain and George Bush and their allies thrust upon us," said Schecter. "We’re much more dangerously overstretched than anything close to where we were back then."

Perhaps the biggest gap in logic for McCain’s use of his experience with defeat in Vietnam to bolster the war effort in Iraq is based on his contention that the US must not lose its will to fight.

"It’s a trick because that observation assumes that the United States could have won in Vietnam if only it had not withdrawn, which is not true," Juan Cole, professor of history at the University of Michigan and a Middle East expert, told IPS. "Yes, it’s very unfortunate to be defeated in a military endeavor, but it happens. So suck it up and get over it."

Cole insists that it is not the lessons of Vietnam, but rather that war’s follies that are being replayed in Iraq.

"McCain and the Republicans misunderstood the North Vietnamese communists as being an international communist threat. But they were just Vietnamese nationalists," said Cole. "Now these same people are misunderstanding the Sunni insurgency as an international al-Qaeda threat. But they’re just Sunni Arab Iraqi nationalists."

After McCain had settled into the realist mindset as he entered politics, he played a major role in normalizing relations with Vietnam after the end of the Cold War  advocating for a US interests section in Vietnam in the early 1980s and traveling to Vietnam in the mid-1990s as part of a push for normalization made official shortly thereafter by Pres. Bill Clinton.

"In a way that was sort of explicitly or implicitly admitting that what we did in Vietnam was an absolute waste of our time. It was a stupid war. It didn’t help our national security; it injured us," said Schecter. "It exacerbated problems just as Iraq is doing now. So now he throws up the same silly platitudes that were used back then about ‘you need to win there.’ Well, what does that mean?"

"In the end, diplomacy is what created the situation we’re currently in our relationship with Vietnam," he said. "Where are we right now? We’re a trading partner of theirs."