NEWS ANALYSIS : The Price of Peace: Hussein’s Ouster : Outcome:The ground campaign raises the cost of war for the allies. The Iraqi leader will have to pay it.

President Bush’s decision to launch a full-scale ground offensive against Iraq does more than take the Gulf crisis to a new military level. It is a political turning point as well, making it more certain than ever that the allies will seek Saddam Hussein’s ouster as part of the price of peace.

The formal goal of the war will remain, as before, the spare objective of the U.N. Security Council: to force Iraqi troops out of Kuwait.

But just as the air war that began last month allowed the United States to go beyond the literal words of the U.N. resolutions and destroy Iraq’s nuclear and chemical weapons plants, so the ground war gives the allies a chance to demolish the core of Iraq’s conventional armed forces.

And, U.S. officials and other experts said, the Iraqi army has always been an indispensable pillar of Hussein’s political power. By humbling it, the allies will be positioned to achieve--directly or indirectly--the crushing of Hussein himself.

“The ground battle is Saddam’s last trump card, and if it doesn’t work, his prestige and his image are shattered,” said William B. Quandt of the Brookings Institution, who served as a National Security Council aide in the Carter Administration.

If the allies win a quick victory on the ground, Quandt said, “Saddam may not survive. And even if he survives, his power is gone.”

Until Saturday evening, a U.S. official noted, President Bush was still prepared to let Hussein withdraw from Iraq while preserving much of his ground army. If Hussein had accepted Bush’s ultimatum to withdraw from Kuwait within seven days, the official noted, “he could have held onto quite a bit of equipment.”

But now, U.S. and allied forces are racing for southern Iraq, seeking to cut off the elite Republican Guard, the pride of Hussein’s armed forces. One of their goals is to destroy or capture every Iraqi unit in the area.

The result could be a fatal humiliation for Hussein.

And--by raising the cost of the war for the allies--it is almost certain to raise the political price Iraq must pay to end the conflict.

In a ground war, “it’s not worth Saudi, American and other coalition nationals’ deaths unless we make sure none of the assets he has in Kuwait or outside Kuwait, including the Republican Guard, has any chance to go home,” a senior allied diplomat said. “Otherwise, it’s a wasted effort.”

“So you will find that the objective will be that, whatever happens, we will grab Kuwait and the Republican Guard like this”--he held his hands close together--”keep them in the middle, and now we dictate what happens.”

Asked if that meant the allies would demand the ouster of Hussein, the diplomat replied with a smile: “We will let other things take care of him.”

The Iraqi military may act to overthrow Hussein if he leads them into a humiliating defeat on the ground, a U.S. official said. “It’s certainly a possibility,” he said.

Also, the fact that allied forces will seize and hold Iraqi territory--even though their governments disavow any intention to keep it--will give the United States and the other members of the coalition enormous political leverage over the final outcome in Baghdad.

Even a temporary allied occupation of southern Iraq would strengthen the coalition’s demand for limits on the number of Iraqi troops that could be stationed near Kuwait’s border, for example.

In that sense, the offensive has allowed Bush and his coalition partners to regain the initiative in a struggle that has alternated between military and diplomatic thrusts. But it also introduces another politically volatile element to the war: the likelihood that Hussein, his back to the wall, may use his vaunted chemical weapons against advancing allied forces.

If that happens, the allied diplomat said, “then all bets are off.”

“We’ll use the unimaginable, short of nuclear weapons,” he said, adding that one option was a “march on Baghdad to find Saddam and kill him.”

Administration officials confirmed that the United States has warned Hussein that the use of chemical warfare would cross a “red line” beyond which the allies would pursue him as a war criminal.

To be sure, if the U.S.-led multinational force runs into stiff resistance and suffers unexpectedly large casualties, that could alter the political dynamic of the war in another sense--by reopening debate at home on the wisdom of President Bush’s leadership.

Historically, from Korea through Vietnam to the Reagan Administration’s deployment of U.S. Marines in Beirut, the American public’s support for military action has consistently dropped as casualties rose.

“It all depends on how quickly and how easily the offensive succeeds,” said Prof. John E. Mueller of the University of Rochester, the nation’s leading scholar of public opinion in time of war. “If so many Iraqis surrender that it turns out to be largely a matter of crowd control, there’s no problem. But after a couple of hundred American casualties, the argument may be made that President Bush could have saved American lives by holding back--and that could be a problem for him.”

Indeed, as late as Saturday morning, some members of Congress--including Senate Republican Leader Bob Dole of Kansas--were still urging Bush to delay a ground war for the sake of American lives.

“It seems to me that the air strategy’s working,” Dole said in an interview on NBC. “If Gen. (H. Norman) Schwarzkopf is right and we’re killing 100 tanks a day, and the Iraqi army could be near collapse, I’m not certain why they want to risk any additional lives.”

“In my view, if the Iraqis are finally trapped and have to defend themselves, there are going to be a fairly high number of coalition casualties,” Dole said. “ . . . Having just talked to a grandmother of one of the young men in my state who lost their lives in combat, I can tell you that we need to minimize our casualties in every way we can.”

That kind of criticism could increase rapidly if casualties are severe.

“If the ground battle should prove unexpectedly difficult, then I think there will be Monday-morning quarterbacking,” said Zbigniew Brzezinski, who was President Carter’s national security adviser. “There will be some criticism of the President’s unwillingness to give Saddam Hussein even the slightest degree of room for a withdrawal.”

The good news for Bush is that he begins with an extraordinarily high level of support from the public--for his decision to launch the ground war as well as his leadership during the last five weeks of air war.

A Los Angeles Times Poll released last week found that 84% of a nationwide sample approved Bush’s handling of the crisis so far, and 78% said they would support a ground war if the President decided it was necessary.

Even among those who said they expect more than 10,000 casualties in a ground war, 60% still said they would support Bush’s decision.

But those numbers could change rapidly, Mueller said. In earlier wars, too, the public’s initial reaction was to support whatever President was in office. Over time, he said, “if you actually did have thousands of American dead, the political result would be disastrous.”

A second bright spot for Bush is the international political environment. His dogged diplomacy--coupled with Hussein’s intransigence--has not only helped the anti-Iraq coalition stay together but deprived Baghdad of support among governments that might otherwise have been tempted to lend it.

Only hours after the collapse of Soviet President Mikhail S. Gorbachev’s attempt to negotiate a compromise, Gorbachev’s spokesman declared that only Iraq was to blame. Even Iran said it would remain neutral because Hussein had failed to withdraw his forces from Kuwait.

And in the Arab world, paradoxically, the advent of a bloody ground war could actually increase popular sympathy for the United States.

“In some ways, it will be viewed as a more legitimate kind of war than the technological mismatch we saw during the air war,” Quandt said. “People in the Arab world objected to the bombing of Baghdad, to the civilian casualties. This is going to be different. This is war fought among soldiers. It’s mano a mano. “