Wars transform nations, but the response to wars can transform them even more.

America's 42-day war with Iraq did little to refashion the American economy, as World War II did, nor did it reshuffle the class structure, create new bureaucratic institutions or establish new ways of governing. Yet, in ways that might best be described as spiritual and intellectual, the clockwork efficiency of the American war effort seemed to change everything.

A nation that had lost faith in government's ability to accomplish anything -- especially through armed intervention abroad -- saw political and military leaders conceive, plan and carry out a brilliantly successful military venture.

Martial values that had fallen into disrepute were revitalized. Presidential authority, under assault since Vietnam, was strengthened.

For the moment, at least, what had been a deeply pessimistic national mood was swept away in a wave of optimism. "People in my state think entirely differently about the country," said Sen. Richard G. Lugar (R-Ind.). No, he said, the problems hadn't changed. "But the spirit to change them has."

Not all Americans welcome the nation's triumphal mood. Some fear it will make the country trigger-happy. Others question its depth. "This war was a vicarious experience," said William Galston, a professor of public policy at the University of Maryland who strongly supported the war. "Except for those who were actually involved, it called for no pain and no sacrifice. Most of us got all the excitement of vicarious involvement in a successful venture and paid nothing."

But from the beginning, President Bush opened a second front in this war, aimed squarely at the audience at home. He led a fierce assault against what had been called "the Vietnam syndrome," and just as the president declared victory over Saddam Hussein, so did he proclaim that the syndrome had been vanquished.

"By God," the president declared on Friday, "we've kicked the Vietnam syndrome once and for all."

There was no more powerful symbol of the transformation than the helicopters landing Marines on the roof of the U.S. Embassy in Kuwait. The last collective memory of helicopters hovering above an embassy involved the chaotic evacuation of Americans and their local allies from Saigon as North Vietnamese troops closed in on the city.

The Vietnam syndrome was open to many interpretations, but more than anything, it was the belief that any large-scale American military intervention abroad was doomed to practical failure -- and perhaps also to moral iniquity.

Rep. Jim Cooper (D-Tenn.), who voted to give Bush authority to go to war, said the Vietnam syndrome was alive and well at the beginning of this conflict and permeated almost everything that was said about it. "A few months ago, we thought that everything would go wrong," Cooper said in a nearly perfect definition of the syndrome, "that casualties would be enormous, that there would be unforeseen catastrophes, that Murphy's Law would prevail."

But Murphy's Law was repealed for U.S. forces in the gulf and the moral qualms of many Americans were resolved by Saddam, whom few saw as being "on the right side of history." Thus, for the first time since Vietnam, American leaders were openly talking about a Second American Century, a time when American leadership really will be able to define the world. "There is a recognition -- explicit and not just tacit -- by the United Nations that the United States is the nation that makes the moral difference and the military difference," said William J. Bennett, a former philosophy professor who went on to serve in the Reagan and Bush administrations.

Such bold talk alarms those who fear that an "Iraq syndrome," a belief in the invincibility of American might, could prove more perilous than the Vietnam syndrome ever was. "We've lowered the threshold to war," said David Boaz, vice president of the libertarian Cato Institute. "Going to war is the most serious decision a society can make, and lowering that threshold creates a lot of dangers."

"All I can say," said Rep. David R. Obey (D-Wis.), "is that I hope it doesn't make the world safe for ill-advised wars." Added Rep. John Lewis (D-Ga.): "I hope we don't get used to war being so easy. War is not a cure-all."

Even Bennett warned that the lessons of beating Saddam's Iraq could be overdrawn. "You're not always going to be blessed with enemies like this, either with their incompetence or their fiendishness," he said.

Nor did the entire country fully share in the mood of optimism. The Rev. J. Bryan Hehir, a professor of ethics and international relations at Georgetown University, said the thrill of victory might be tempered when Americans realize how many Iraqis were killed by American weaponry. Black Americans were notably less receptive than whites toward the gulf war and are, according to the polls, less bullish on the future than whites.

Lewis, a veteran of the civil rights movement, said he believes the attitude of black Americans toward the war was conditioned not only by the presence of large number of black troops in the gulf, but also by the depth of the economic problems blacks confront and by anger at the president's veto of the 1990 Civil Rights Bill -- at the very moment when he was calling for liberty for Kuwaitis. Other black leaders questioned why American solicitude for Kuwait's freedom had not been matched by a comparably strong commitment to the rights of black South Africans.

Hehir believes that today's talk of the end of the Vietnam syndrome is exaggerated. To the extent that the syndrome is defined as a revulsion against protracted and uncertain commitments, which is precisely what the war with Iraq was not, the latest conflict has done nothing to erase it. As for other forms of foreign intervention, Hehir said, Americans had long ago kicked their inhibitions.

"I think the Vietnam syndrome has been overplayed for a long time," he said. "We used force against Gadhafi, we used force against Panama, we used force against Grenada. Although these were relatively small engagements, we clearly were not restrained in our use of force."

To the extent that attitudes have changed, there will be debate over the impact on the conduct of American policy. Rep. Barney Frank (D-Mass.) noted that there are few apparent threats comparable to that posed by Saddam before the war and thus few cases in which the United States will even be tempted to use its military power.

Frank also argued that contrary to the currently popular view that the war will provide a boost to the military budget, it could ultimately reduce support for military spending. The breadth of the United States victory, he suggested, could make Americans feel incomparably more secure. Iraq, Frank said, "turned out not to be as great a threat as we feared -- we have a very considerable margin of safety."

Frank's comments reflect the beginning of what could prove an even more important war than the one just ended: the battle over how to interpret "the lessons of Iraq."

Liberals and Democrats, many of whom had opposed going to war, were quick to argue that the success of this collective, government-led enterprise should prove to Americans that they can expect more and get more from government -- at home as well as abroad.

"It sets a new standard for people to judge government by," said Rep. Robert E. Wise Jr. (D-W.Va.). In the Persian Gulf, he said, "government set a goal, mobilized half a million people, moved more materiel than at any time since World War II. Why can't you do the same thing in education, in infrastructure, in health care?" In the sort of line Democrats will be using a lot, Wise added: "If Bush had run the war the way he runs domestic policy, Saddam Hussein would be in Rome today."

Scott Lillie, the executive director of the Democratic Study Group, said the war would also encourage Americans to raise questions about the nation's lack of economic competitiveness -- and what role the government can play in fostering ingenuity.

"If you can design and develop a Tomahawk missile," he said, "then there's no excuse not to be competitive in the production of lower technology items such as consumer electronics." Liberals, in short, want to change the subject from the Iraq military threat, to Japanese and Western European economic competition.

Shrewd conservatives such as Bennett contend that the military is a distinctive institution far removed from the workings of social service agencies or even the educational system. "There's no domestic equivalent of the Scud or the Patriot," Bennett said.

Galston believes the war's greatest domestic impact will be on the values Americans most respect. He sees the war encouraging a shift from individualistic values encouraged -- in very different ways -- during both the 1960s and 1980s, and toward what he called "blue-collar values."

"Blue-collar values," Galston said, "involve such things as patriotism -- the disposition to believe that your country is more likely to be right than wrong -- self-discipline rather than self-expression, respect for authority rather than the critique of authority, a substantial measure of self-restraint as opposed to immediate gratification, and the notion of something larger in which you invest yourself."

Patrick J. Glynn, a conservative scholar at the American Enterprise Institute, believes that the long-term lessons of both Iraq and Vietnam concern how the country decides whether to go to war and how committed it is to a successful outcome. "If you go to war," he said, "you have to be engaged and you have to believe in what you're doing. You're killing people and risking being killed, which is about the most serious thing human beings can do."

Glynn argues the on-again, off-again tactics used in Vietnam -- involving gradual escalation and periodic bombing halts -- reflected the Johnson administration's ambivalence about the war.

By contrast, he said, the Iraqi war won congressional approval after an open debate and Bush was unequivocal in arguing that the war was just and necessary. Because of that process, he said, the military was allowed to pursue victory and the public came to see victory as desirable.

The current exultation could be quickly dampened by the difficulties of making peace in a complicated region. Or it could be slowly eroded as Americans contemplate the moral rectitude of gleefulness in the face of a victory gained largely through the enormous destructive power of modern weaponry.

What could last longer is the aspect of triumph having less to do with sheer firepower and more to do with collective commitment, technological prowess and tactical shrewdness. The current celebrations, said Lugar, reflect Americans' relief at their nation's collective competence after a period when they had started to think of their country as just "one of the pack."

"If you have genuine heroes like {Gen. Colin L.} Powell and {Gen. H. Norman} Schwarzkopf," said Larry Smith, counselor to the House Armed Services Committee, "it is because they are people who proved that they could outthink the other guy. It's revisiting an older idea of ourselves -- that we are an ingenious people."