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By the time these Americans were lifted off a roof in Saigon in 1975 , few American combat forces were left in Vietnam.

Now, in urging Americans to stay the course in Iraq, President Bush is challenging that historical memory.

In reminding Americans that the pullout in 1975 was followed by years of bloody upheaval in Southeast Asia, Mr. Bush argued in a speech on Wednesday that Vietnam’s lessons provide a reason for persevering in Iraq, rather than for leaving any time soon. Mr. Bush in essence accused his war critics of amnesia over the exodus of Vietnamese “boat people” refugees and the mass killings in Cambodia that upended the lives of millions of people.

President Bush is right on the factual record, according to historians. But many of them also quarreled with his drawing analogies from the causes of that turmoil to predict what might happen in Iraq should the United States withdraw.

“It is undoubtedly true that America’s failure in Vietnam led to catastrophic consequences in the region, especially in Cambodia,” said David C. Hendrickson, a specialist on the history of American foreign policy at Colorado College in Colorado Springs.

“But there are a couple of further points that need weighing,” he added. “One is that the Khmer Rouge would never have come to power in the absence of the war in Vietnam — this dark force arose out of the circumstances of the war, was in a deep sense created by the war. The same thing has happened in the Middle East today. Foreign occupation of Iraq has created far more terrorists than it has deterred.”

The record of death and dislocation after the American withdrawal from Vietnam ranks high among the tragedies of the last century, with an estimated 1.7 million Cambodians, about one-fifth of the population, dying under the rule of Pol Pot, and an estimated 1.5 million Vietnamese and other Indochinese becoming refugees. Estimates of the number of Vietnamese who were sent to prison camps after the war have ranged widely, from 50,000 to more than 400,000, and some accounts have said that tens of thousands perished, a figure that Mr. Bush cited in his speech, to the Veterans of Foreign Wars. Mr. Bush did not offer a judgment on what, if anything, might have brought victory in Vietnam or whether the war itself was a mistake. Instead, he sought to underscore the dangers of a hasty withdrawal from Iraq.

But the American drawdown from Vietnam was hardly abrupt, and it lasted much longer than many people remember. The withdrawal actually began in 1968, after the Tet offensive, which was a military defeat for the Communist guerrillas and their North Vietnamese sponsors. But it also illustrated the vulnerability of the United States and its South Vietnamese allies.

Although American commanders asked for several hundred thousand reinforcements after Tet, President Johnson turned them down. President Nixon began a process of “Vietnamization” in which responsibility for security was gradually handed to local military and police forces — similar to Mr. Bush’s long-term strategy for Iraq today.

American air power was used to help sustain South Vietnam’s struggling government, but by the time of the famous photograph of Americans being lifted off a roof in Saigon in 1975, few American combat forces were left in Vietnam. “It was not a precipitous withdrawal, it was a very deliberate disengagement,” said Andrew J. Bacevich, a platoon leader in Vietnam who is now a professor of international relations at Boston University.

Vietnam today is a unified and stable nation whose Communist government poses little threat to its neighbors and is developing healthy ties with the United States. Mr. Bush visited Vietnam last November; a return visit to the White House this summer by Nguyen Minh Triet was the first visit by a Vietnamese head of state since the war.

“The Vietnam comparison should invite us to think harder about how to minimize the consequences of our military failure,” Mr. Bacevich added. “If one is really concerned about the Iraqi people, and the fate that may be awaiting them as this war winds down, then we ought to get serious about opening our doors, and to welcoming to the United States those Iraqis who have supported us and have put themselves and their families in danger.”

To that end, some members of Congress and human rights groups have urged the Bush administration to drop the limits on Iraqi refugees admitted to the United States.

Mr. Bush also sought to inspire renewed support for his Iraq strategy by recalling the years of national sacrifice during World War II, and the commitment required to rebuild two of history’s most aggressive and lawless adversaries, Nazi Germany and Imperial Japan, into reliable and responsible allies.

But historians note that Germany and Japan were homogenous nation-states with clear national identities and no internal feuding among factions or sects, in stark contrast to Iraq today.

The comparison of Iraq to Germany and Japan “is fanciful,” said Steven Simon, a senior fellow at the Council on Foreign Relations. He noted that the American and allied militaries had eliminated the governments of Japan and Germany, and any lingering opposition, and assembled occupation forces that were, proportionally, more than three times as large as the current American presence of more than 160,000 troops in Iraq.

“That’s the kind of troop level you need to control the situation,” Mr. Simon said. “The occupation of Germany and Japan lasted for years — and not a single American solider was killed by insurgents.”

Senior American military officers speaking privately also say that the essential elements that brought victory in World War II — a total commitment by the American people and the government, and a staggering economic commitment to rebuild defeated adversaries — do not exist for the Iraq war. The wars in Korea and Vietnam also involved considerable national sacrifice, including tax increases and conscription.   This was Posted 6 hours ago by the washington post