For 74 days, U.S. forces pounded the enemy's elite units almost at will. Huge Superfortress bombers dropped 6,800 tons of high explosives. Battleships fired 21,926 rounds, including 203 crippling 1-ton shells from 16-inch guns.

When the timing was judged to be ripe, the Marines went in. Their commanders expected them to prevail within days. Instead, the battle lasted five weeks.In the end, virtually all of the 23,000 enemy soldiers were killed, but at horrific cost. The Marines lost 5,391 dead and 17,400 wounded - or one U.S. casualty per enemy soldier killed.

The battle of Iwo Jima in 1944 evokes ominous comparisons to what could soon be the battle of Kuwait: crack divisions, dug into trenches and caves, well-fortified and well-armed, holding out against a murderous air campaign while inflicting devastating ground casualties in literally a fight to the death.

As President Bush ponders how and when to launch a ground attack against 540,000 Iraqi forces in Kuwait, he is burdened by opposing pressures as great as those encountered by U.S. leaders late in World War II.

Bush faces not only certain U.S. casualties but also their impact at home and abroad, along with the repercussions of going in or not going in - and precisely when. A key decision is whether to continue the air strikes for weeks or months to save U.S. lives while risking defections by Arab members of the allied coalition.

As Bush's top two military advisers discuss the ground attack options in Saudi Arabia this weekend, the strategic questions confronting Bush are complex.

A prewar study by the Army War College said a ground war to drive Iraq from Kuwait would be "hideously expensive" and would "exact a high price on the winners as well as the defeated."

The pivotal battle at Iwo Jima is a reminder that even massive aerial and naval bombardments are no guarantee of light ground casualties. The elite Japanese Special Naval Landing Force, like Iraq's crack Republican Guard, held out because of extensive bunkers, tunnels and excavations.

"The lesson we learned at Iwo Jima is that air poweralone is not sufficient against a dug-in, motivated army," said Robert Pape Jr., who specializes in air strategy at the Center for International Peace and Security at the University of Michigan.

However, Pape added, "air power can mean the difference between a quick, decisive victory or a protracted war of attrition - the difference between, say, 10,000 (allied) casualties or 70,000" in a Persian Gulf ground war.

Determining when air power has sufficiently weakened an enemy was difficult in World War II and Vietnam. In the gulf war, it is virtually impossible because of the way the Iraqis have dug in and taken steps to mask damage, Pape said.

Iraq has used aluminum sheeting to draw attacks on empty bunkers and decoy tanks, burned oil to simulate hits on bunkered tanks, painted craters on runways, set up dummy targets and pulled men and weapons in and out of bunkers in a desert shell game. Throughout, the army's true strength and morale remains hidden.

"This campaign is unprecedented," said Stephen Biddle, a defense analyst in Washington who specializes in air warfare tactics. "We've never come up against someone who would just dig in, just sit there and take this pounding day after day."

Schwarzkopf put it more bluntly: "In a mad dog, there is no predictability."

A key factor is the Iraqis' will to fight. If Pentagon assertions of widespread low morale prove false, a spirited defense would add to the allied death toll.

Even if the 50 percent attrition of the enemy's heavy weapons is not met, Pape said, every Iraqi tank or artillery piece destroyed is one less weapon U.S. troops will have to kill.

"You want to kill enough now so that you're able to defeat their forces on the ground without running out of planes" during ground battles in which U.S. forces would have massive air cover and the Iraqis would have none, Pape said.

He said the only way to draw Iraqi tanks, artillery, armored vehicles and men from their bunkers and expose them to allied air supremacy is to confront them with ground troops.

The irony of this strategy is that Bush would not know if a decision to launch a ground war was correct until bloody fighting was well under way. Only then would the effectiveness of air strikes be revealed.

" By then, it's too late to change anything," Biddle said. "Basically, you're just satisfying your curiosity."