By Paul Reynolds
World affairs correspondent, BBC News website
President Bush is seeking to redeem the Vietnam War.
President Bush defends the wars in Vietnam and Iraq
He has tried to turn conventional wisdom about that war (that it was a quagmire and a sideshow in strategic terms) on its head.
In his speech to the Veterans of Foreign Wars, he presented Vietnam as part of a pattern of American operations in the Far East in which Japan had been democratised and South Korea liberated - despite, he argued, the opposition of "experts" of the day.
Vietnam was a war, he suggested, that was worth fighting. And his message was clear - so, too, is the war in Iraq.
The US withdrawal from Vietnam, he argued, led to more suffering, not less. Just as it would, he implied, in Iraq, with the added danger in Iraq, he claimed, that al-Qaeda would be emboldened.
Three weeks before his administration presents its assessment of the Iraq war to Congress, Mr Bush is signalling that the US will not leave Iraq on his watch (which ends in January 2009). This speech followed a significant phrase he used in a radio address on 11 August that the surge of US troops in Iraq was in its "early stages."
The Vietnam connection
The introduction of Vietnam into the argument is fraught with difficulties.
His speech re-opens an old issue over President Bush. Are his claims reality or exaggeration?
The example of Vietnam might appeal to the veterans who fought there and to a new generation that did not experience the divisions that it wrought in US society. It will appeal to American pride and patriotism and seeks to throw critics of the Iraq war onto the defensive.
But using Vietnam as an analogy might not appeal to the American people as a whole. For them, Vietnam has always been a failure and any comparison with it evokes that failure.
And warnings do not always get heard. Americans, after all, were warned of disaster if South Vietnam fell. Yet that did not happen. The dominoes of Thailand, Malaysia, Singapore and the Philippines did not fall to communism. They thrived. And the United States went on to win the Cold War.
A lesson of Vietnam is that predictions are so often precarious.
Was it winnable?
Mr Bush himself did not say so, but some participants like the former US Secretary of State Al Haig have argued that Vietnam was "winnable". Almost no military historians have agreed.
The US and the South Vietnamese government were facing not just a guerrilla war in South Vietnam led by the Viet Cong but large-scale assaults from the North Vietnamese army. North Vietnam was led by committed ideologues who were quite determined to achieve their goals whatever the cost. They had seen off the French and would see off anyone else.
The Americans tried all the tactical variations. Kennedy sent thousands of military "advisers" (the question being, of course, whether he would have sent major combat units). Johnson escalated the war into a massive commitment.
"Search and destroy" sweeps, attacks on North Vietnamese supply lines and the North itself, the herding of villagers into encampments, napalm bombing - everything regarded by the Americans as within the bounds of acceptable warfare at that time was tried.
Then American public support collapsed, their troops left and they tried Vietnamisation. They handed the war over to the South Vietnamese army. That, too, failed.
President Bush argued that the price of the US withdrawal "was paid by millions of innocent citizens whose agonies would add to our vocabulary new terms like 'boat people', 're-education camps', and 'killing fields'."
It is interesting to note his use of the word "citizens" to describe the Vietnamese and the Cambodians. It dignifies the war as well as them (though it was not a word used by US troops much) and it hints that other "citizens" (including American ones) will suffer if Iraq, too, is abandoned.
He did not say there would have been suffering and death if the Americans had stayed to fight it out.
Another argument he used was that the massacre of the Cambodian population by the Khmer Rouge was the result of the failure in Vietnam.
It is true that the Khmer Rouge gained power in Cambodia the same year that North Vietnamese did in South Vietnam - 1975.
But the seeds of their success had been sown much earlier and the effect of the US bombing of Cambodia (to attack North Vietnamese bases there) is thought to have increased support for the Khmer Rouge to an ultimately disastrous extent.
It was in fact left to Vietnam to invade and remove the genocidal Khmer Rouge in 1979.
Ultimately, the war in Iraq will not be won in arguments over Vietnam.
The fact that President Bush is making these arguments shows how determined he is to stay in Iraq.