Exactly two weeks to the day before war began and to almost the precise hour, many Americans heard George Bush passionately express his rationale for doing whatever was necessary to stop Saddam Hussein's aggression. Nothing less than lasting peace, stability and security in the Persian Gulf region and a new world order were at stake, he told David Frost in a televised conversation broadcast over PBS. Bush added fervently: "It's that big. It's that important. Nothing like this since World War II. Nothing of this moral importance since World War II."

It was an extraordinarily revealing statement and not just because it illuminated how in Bush's mind the looming Persian Gulf War eclipsed all other events since World War II in importance. That historical comparison alone was remarkable, for that was the period in which America rebuilt Europe after the ravages of World War II through the Marshall Plan, fought and won the Cold War that led to the collapse of communism, demonstrated willingness to expend blood and treasure in the hot wars of Korea and Vietnam and became the most powerful nation ever.

Even more striking about Bush's remarks was the way in which he cast the struggle against Saddam in stark moral terms. It was "such a clear case," he said, of "good versus evil. We have such a clear moral case."

This was not the first time that Bush made his case for waging war in moral absolutes. From the beginning of the crisis last August, he repeatedly has cited moral principles as reasons to combat the "new Hitler."

Not since Woodrow Wilson, the supreme idealist whose self-appointed mission was to do good in the world, has an American president led the nation into war under such moralistic banners. To Wilson, America's entry into World War I was a moral crusade: The Great War would make the world "safe for democracy." To Bush, the gulf war represents much more than defeating a brutal Third World tyrant. It symbolizes a cause for which "no price is too heavy to pay" and represents nothing less than "the promise now of a much more peaceful world."

There's no reason to doubt Bush's sincerity. Those who know him well say these beliefs are consistent with everything that he stands for and spring naturally from his family background, his World War II combat service and his experience since then, including that at the United Nations and Central Intelligence Agency.

Now that combat has begun, however, there are reasons to wonder whether the American people view the war against Iraq in such moral-crusade terms or understand what Bush means by that "new world order" that he mentions so frequently -- especially as it applies to the turbulent Mideast. Even more reason for doubt exists about whether Bush has prepared the public for the costs of this war and the potential heavy loss of life if land assaults are necessary.

The first week of war suggests that the air war, for all its overwhelming power, is unlikely to be decisive. Despite the continuous rain of bombs and missiles on Iraq and its troops, an assault unmatched for sheer destructive conventional force in any previous war and about which we still know too little, it appears that the enemy is largely intact and capable of delivering heavy blows. Also unclear is that massive air war's effect on the Iraqi people, not only in civilian casualties and morale but in engendering hatreds that could last long after war ends.

If a bloody land war occurs, those hatreds almost certainly will intensify.

What, then, of prospects for the new world order and Bush's dream of achieving "lasting peace and stability"?

In this, the best exposition I've heard came from the president's budget director, Richard G. Darman, during a recent conversation with Washington Post colleague David S. Broder and myself. Discussing the difficult choices involved in drafting a budget to deal with America's new needs for war and old ones not met at home, Darman remarked that they paled beside the stakes in the gulf. "If this really is the start of the world that can enforce civilized norms in ways where the next Saddam Hussein doesn't even try aggression," he said, "that is a radical shift in human history."

So it would be. But there are other forms of what Winston Churchill called "the Terrible Ifs of history" present in this crisis.

If an international precedent for ensuring peace is established, if the next aggressor is not tempted to aggress, if the world's most dangerous arena of regional conflicts becomes more stable, then will the new world order emerge? Bush's great gamble and moral crusade depends on answering each of those questions affirmatively, and therein lies the biggest "if" of all.