100 to 5,000, with total numbers of wounded about three to four times as great. This range is wide. But it is important to recognize that, based on available methodologies for predicting combat outcomes, anything in this range is plausible. Those in the public policy debate who insist that any war would be a walkover have the onus on them to explain why. At the same time, there would appear to be little chance of any war against Iraq bogging down into the type of quagmire in which combat could last years and entail many many thousands of American deaths. Invading Iraq would not be another Korea or Vietnam.

The second main theme is that Iraqi civilian casualties could be substantial in such a war, given the assumption that it would unfold largely in Iraq's cities. In approximate terms, casualties might be ten times as great as those of the U.S. military, if not more. This fact could pose pressures and problems for any Arab governments supporting the United States in such a war. Among its other implications, this is a strong argument for trying to defeat Iraq rapidly and with overwhelming force, so that the pressure of the "Arab street" can be contained. Civilian casualties due to clandestine or terrorist attacks are also possible in places such as Kuwait, Israel, and the United States, with plausible mortality ranges in the high hundreds of individuals.

The War Scenario

Consistent with military and strategic logic, and with leaked Pentagon war plans from the summer of 2002, I assume that a war to overthrow Saddam would involve about 250,000 American forces. The Afghanistan model of warfare, in which small numbers of U.S. special forces and American airpower work with indigenous opposition groups to fight government forces, would almost surely not work in Iraq, as discussed further below. That is due to relative weakness of the Iraqi opposition as well as the Iraqi military's ability to hole up in cities, where American airpower is far less effective than in open terrain. Modest-sized operations, involving perhaps 50,000 to 75,000 U.S. troops, are somewhat more promising. But they would run the risk of encountering serious difficulties in the urban centers of Iraq. Relatedly, Iraqi forces would be less likely to capitulate quickly if they sensed they had a chance to prevail, increasing the chances of a prolonged urban battle under such circumstances.

This is not to say that a larger operation would have to mirror Desert Storm in its basic concept. The invasion might involve rapid airborne or commando strikes against Iraqi command and control assets as well as weapons of mass destruction sites in the earliest hours of combat, even as main invasion forces march more slowly through Iraq towards Baghdad and other cities. It might also use relatively small teams of American ground forces perhaps brigade-sized units of several thousand troops each-to try to lure Iraqi forces out of the cities into regions where they would be more vulnerable to American airpower (and to lure out defectors to join U.S. forces). These sorts of "insideout" tactics would try to avoid the delays inherent in a mechanized march from Kuwait and other neighboring countries to Baghdad. But they would be gambles, and the United States would need backup forces in place in case the gambles did not pay off.

Forecasting Casualties in Infantry and Urban Combat

Operation Desert Storm and, more recently, Operation Enduring Freedom in Afghanistan probably do not provide much insight into the likely nature of a future war in Iraq. Saddam seems unlikely to place many of its forces in the open in a future war. Because Iraq knows its weaknesses against the U.S. military in open settings, and because it is Saddam Hussein's regime and weapons of mass destruction capabilities that would be at issue in a future war, one has to assume that the combat would be primarily urban.

This fact immediately changes the calculus of a future war by comparison with Desert Storm. To begin, airpower would be much more difficult to employ against Iraqi forces that could intersperse themselves with civilian vehicles and populations. This type of tactic was employed near Basra during Desert Storm, and has been employed in the subsequent eleven years as Iraqis have sought to place valued military assets near civilian populations to make it harder for the United States to bomb them. Iraqi forces have much better cover within cities, or even forested regions, than in open desert. As one further demonstration of this rather obvious fact, recall that even after eight years of further modernization after Desert Storm, NATO airpower was of quite limited effectiveness against small groups of Serb forces operating within forests, towns, and civilian populations in the Kosovo war. If U.S.-led forces tried to fly low to find enemy forces against this complex backdrop, they would have to contend with an Iraqi air defense network consisting, among other things, of some 6,000 air defense guns and 1,500 surface-to-air missile launchers (including man-portable SAMs).3

Nothing about new technology and new warfighting concepts associated with the socalled revolution in military affairs seems likely to radically change the challenge of urban warfare anytime soon. For example, recent Marine Corps experiments incorporating such new concepts suggested that U.S. troops could still suffer quite high casualties in urban combat.

Historical Parallels

Two recent conflicts may provide better indicators of the likely nature of a future U.S.Iraq war: the 1989 invasion of Panama and the 1993 U.S. experience in Mogadishu, Somalia. In December, 1989, U.S. forces overthrew Panamanian strongman Manuel Noriega and defeated his armed forces. About 22,500 American personnel participated. The operation involved simultaneous nighttime airborne operations against 27 objectives throughout the country. Special forces infiltrated key sites shortly before the airborne assaults to take down Panamanian communications and oppose any attempts by Panama to reinforce its forces under attack. The massive, simultaneous assault against Panama 's 4,400-strong defense forces and its paramilitary forces of several thousand more personnel overwhelmed the latter, surprising them with its ferocity and coordination in the opening hours of battle. Twenty-three Americans died, as did about

125 Panamanian military personnel. Perhaps 200 to 600 Panamanian civilians died as well.

In the Somalia experience, U.S. forces faced ragtag militia opposition. Somali fighters had access to plentiful automatic weapons, rocket-propelled grenades, and mines, but not much more than that, and they were not trained in combined-arms or coordinated military operations. As is well known, the United States had 18 soldiers killed in action on the night of October 3-4, 1993 in the course of a raid on a building where leaders of the Aideed faction were meeting. The tragedy occurred when two helicopters were shot down by rocket-propelled grenades; additional American casualties were suffered in the effort to rescue any of the crew members that might have survived those crashes. Only about 2,000 U.S. forces were deployed for conducting and supporting such raids at the time they occurred; only 160 participated in the October raid. Estimates of Somali militia strength were in the many thousands, with losses on October 3-4 alone estimated at 300 or more combatants. Often forgotten is that a number of other American troops died in Somalia. In fact, total losses reached 29 from hostile action and 14 from "nonhostile" action such as accidents.

What do past cases tell us about how a future war conducted largely in the streets of Baghdad might play out? As discussed in the link, two useful parallels are the U.S. experience in Mogadishu in 1993 and the U.S. invasion of Panama in 1989. Iraqi forces are almost surely better armed and better trained than the military or paramilitary organizations we fought in those cases. Thankfully, they are probably also far less motivated.

That said, it is important to remember that the Iraqi Republican Guard forces fought reasonably hard in Desert Storm. They also enjoy a number of benefits from Saddam's regime and they are rather heavily implicated in his rule. They would probably fear retribution from an alternative regime or from western occupying forces much more than they would fear Iraqi opposition forces and American airpower on the battlefield. How much they would fear American invasion forces, and thus when they would choose to surrender, is difficult to determine. Whether they could be convinced to desert Saddam by an amnesty offer or a promise of protection and inclusion in a post-Saddam regime is an open question. Whether Saddam's commanders could be deterred from using weapons of mass destruction by threatening to hold them personally responsible should they do so is also unclear.

Simply scaling the results of Panama for the size of the Iraqi military leads to an estimate of about 2,000 killed Americans, more than 10,000 dead Iraqi military personnel, and tens of thousands of dead Iraqi citizens. If however it is only the elite Iraqi forces that fight hard, numbering somewhat more than 100,000 Republican Guard, Special Republican Guard, and palace guard forces, extrapolation from the Panama case suggests that losses on all sides might be only one-fourth as great.

The Somalia analogy is also worth invoking. The firefight on the night of October 3-4 can be used as a way to generate pessimistic estimates of how war in Baghdad might

go. As noted, that operation involved about 160 Americans against a single objective, together with roughly a dozen ground vehicles, and more than a dozen helicopters. Overall operations in Baghdad might be 50 to 100 times as large, in any initial assault wave to secure key facilities (recall that 27 objectives were attacked in much-smaller Panama). With comparable casualty rates on a per person basis, U.S. losses could number 1,000 or more just in this phase of the fighting.

The Likely Implications of Weapons of Mass Destruction

One major wild card remains: the likely consequences of any traqi use of weapons of mass destruction. Consider first SCUD attacks against Iraq's neighbors. Even if using chemical or biological agent, they seem a relatively minor threat, given the general difficulty of delivering such agents via missile and the specific limitations of the SCUD. Iraq may still have up to two dozen such missiles. But it often broke up in flight during Desert Storm and has clearly not benefited from extensive flight testing to improve its performance since then. Delivering chemical or biological agent is best done at a steady altitude by an aircraft that spreads the agent over a large area, not by a rapidly descending ballistic missile that may disperse the agent too soon or too late-and in any case, probably in far too concentrated a dose in one place. Should that one place be a sports stadium or other congregating place, results could be disastrous. But given the SCUD's inaccuracy, that would require extreme luck on the part of Iraq.

Second, Iraqi attacks against civilian populations in places such as the United States could be serious, especially if they involved biological agents, in which case plausible casualties could reach into the hundreds or even the thousands. Iraqi special forces have not focused on preparing for such attacks in the past; they have reportedly been devoted to efforts to acquire technologies for producing weapons of mass destruction. It is also unlikely that Iraq has access to the most dangerous pathogens such as smallpox. On the other hand, Saddam may be willing to provide such agents to Hezbollah or al Qaeda operatives under certain circumstances. On balance, the threat from such weapons is rather finite-but also quite real.

Third, Iraq could increase casualty levels of coalition forces by using WMD against them, particularly its thousands of chemical-filled artillery shells and rockets. But it would probably increase casualties by no more than 10 to 20 percent, given historical precedent in conflicts such as the Iran-Iraq war; indeed, U.S. forces are much better equipped to protect themselves from such attacks than most militaries have been in the past. However, Iraq might gain some advantages nonetheless, if at a huge cost to its own civilian populations (and perhaps to its own troops, should winds shift). It could oblige coalition forces to fight in protective gear, slowing operations and generally complicating the mission. If the effects of fighting in such gear were comparable to those of fighting in bad weather or difficult terrain, for example, the pace of coalition fighting and the effectiveness of coalition forces might decline 25 to 50 percent, and casualties might mount by a comparable percentage.

Summary

The United States and coalition partners would win any future war to overthrow Saddam Hussein in a rapid and decisive fashion. This would not be another Vietnam or another Korea. But casualties could be significantly greater to all concerned parties than in the 1991 Persian Gulf War. The best analogy for what such combat could involve would not be Desert Storm, but instead the 1989 U.S. invasion of Panama—and on a much larger scale.

In rough terms, U.S.-led forces might suffer 100 to 5,000 forces killed in action in such a future war. The lower half of that range is perhaps the most plausible. But there is a very real possibility that American deaths could exceed 1,000 in number, and several thousand deaths cannot be ruled out.

By the methodologies employed here, Iraqi troop losses might be expected to roughly 2,000 to 50,000. And civilian deaths could number in the tens of thousands as well. Casualties in countries such as Israel and the United States, not so much from SCUD missiles or other military delivery vehicles as from action by Iraqi-supported terrorists or special forces, could number in the thousands if Saddam provided them with weapons of mass destruction. But such losses might also be trivial in size.

As such, those who feel strongly that a future war against Iraq would be either a cakewalk or a debacle should be challenged to explain why. Historical data and combat models put the onus squarely on those who would make such confident predictions. A quagmire in Iraq seems extremely unlikely. But on the other hand, to count on easy victory, as many American proponents of war seem to do, is not only unsupportable by the available evidence and by the methodologies of combat prediction. It is also irresponsible as a basis on which to plan U.S. military strategy in any future war against Saddam Hussein.

III. WHAT TYPE OF WAR WOULD IT BE?

Iraq, unlike Afghanistan, is located in the heartland of Arabia, a region whose stability is a critical U.S. interest. A prolonged war there could undermine regional stability, put enormous pressure on friendly Arab regimes and Turkey, increase the terrorist threat against the United States, and wreak havoc on oil markets. Accordingly, if Saddam's regime is to be removed militarily, the action must be quick and decisive, and order must be subsequently maintained for as long as it takes to generate a stable and unthreatening replacement government. In addition, to minimize the chances of concerted Iraqi resistance, the U.S. force should be as intimidating and overwhelming as possible. These requirements mean that the United States must be prepared to deploy a large invasion force—at least 200,000 troops, backed by some 1,000 aircraft— and to keep many of them in the region for some time.