Jargonand other grating locutions are among the hazards of war on the home front. Americans are learning this as they learn to use the military verb "to attrite."

Saddam Hussein hopes to force America to fight on the ground before air bombardment has substantially "attritted" his defenses. Iraqi and U.S. forces locked even momentarily in equilibrium on the ground would provide the stark symmetry that would serve Saddam's political aims if he survives to boast about it.

Saddam's aim is for American casualties to reach the threshold at which U.S. decision-makers flinch from the additional violence required to eliminate his regime. His premise is: If he survives the fighting, he wins. So his war aim is to prevent America's achievement of an objective America has not yet set: something approaching unconditional surrender.

Most victories have been something less than total, often because the victors wanted it that way. The cost of achieving or administering unconditional surrender can be prohibitive.

American policy is to inflict from the air sufficient attrition on Iraq's defenses to achieve American war aims -- whatever they eventually will be -- without crossing the crucial threshold to intolerable casualties.

What is that threshold? No one knows. And no one knows how long the battle now raging will last, because no one knows the dynamics of today's battlefield. But according to John Keegan, one of today's foremost students of battles, for centuries battles have become bigger, longer and more lethal.

Agincourt (1415) lasted just a few hours. Waterloo (1815) was a three-day ordeal for some soldiers, a day for most. Gettysburg (1863) spanned three days. But in the First World War, Passchendaele lasted three months, the Somme four, Verdun 10. Battles have become more intensely lethal as they have lengthened. A particular British battalion that suffered 61 percent casualties at Waterloo and 70 percent at the Somme 101 years later suffered its casualties at Waterloo in three hours and those at the Somme in 30 minutes. The width of the "killing zone" was 200 yards at Agincourt, half-a-mile at Waterloo and nearly five miles at the Somme.

In spite of all the tanks and planes, most of the fighting in the Second World War was, says Keegan, "as earthbound, snail-paced and soft-skinned a business as it had been for the 200 preceding years." There were a quarter-of-a-million tanks manufactured during the Second World War.

But, says Keegan, the tank, "though it has transformed the pace and appearance of modern campaigning, has not changed the nature of battle. The focus of fighting may be shifted 20 miles in a single day by an armored thrust, but wherever it comes to rest there must take place exactly the same sort of struggle between man and man which battlefields have seen since armies came into being."

What has changed radically, even in recent decades, is the intensity of the ground combat experience. For about half-a-century, it was thought that the introduction of gas into warfare by the Germans at Ypres in 1915 brought unsurpassable (short of nuclear weapons) deadlines to the battlefield. But, says Keegan, subsequent advances in metallurgy and projectile design enable mechanical killing devices to make the battlefields even more lethal by filling the air with metal.

Rather than training individual marksmen to hit particular targets, armies now train small infantry groups to create an impenetrable zone. Many automatic weapons are effective only for filling a small area with bullets, an activity requiring no more skill than spraying a kitchen with an aerosol insecticide. Infantrymen carry automatic weapons and lightened ammunition in quantities two to three times larger than their Second World War counterparts.

What Keegan calls a "new superfluity of killing agents," buried beneath the soil (mines) and wafted by breezes (gas) and in solid form in the air (other projectiles), makes today's battlefields more lethal than previous ones.

Preliminary "softening" of defenses can help. But there are no guarantees. In the First World War, artillery bombardments that preceded offensives usually did not destroy the dominance to the defenses. Neither, in the Second World War, did air and naval bombardments of Japanese strongholds such as Tarawa, Iwo Jima and Okinawa. Iraq is practiced and skillful at the engineering and tactics of defense. And Desert Storm confronts a new factor complicating offensive action:

Wednesday's Wall Street Journal reported: "Soldiers in the Army's elite Seventh Corps, which is likely to play a leading role in a ground offensive, have stayed up in recent nights, sitting in their hot chemical-warfare suits in response to alerts. Some officers worry that the nightly alarms will hurt their troops' fighting ability."

This could cause commanders to think they face a "use them or lose them" dilemma. But given what we know about likely losses from ground combat, the most welcome words spoken at Wednesday's briefing were from Gen. Colin Powell: "We're in no hurry."