For months, President Bush has been asserting his intention to remove Saddam Hussein from power in Iraq. That goal appears to have broad support from the American people and Congress.
Through careful diplomacy, he can probably also gain at least the acquiescence _ if not the active support _ of a number of European and Arab allies.
A military operation to remove Hussein, however, would be the most momentous use of force by the United States since the Vietnam War. If Bush undertakes such a mission, it will dominate his remaining term, radically reshape the politics of the Persian Gulf and Middle East, and have major repercussions for the global economy.
Yet there has been little debate about the pros and cons of such a war. Senate Foreign Relations Committee hearings planned for next week will be a start, but only a start.
The track record suggests that the United States can continue to contain Hussein without war, just as it deterred the Soviets during the Cold War and just as we have contained North Korea for half a century.
Hussein values his hold on power and his life more than anything and has refrained from actions likely to lead to his downfall. Yet there is a serious case for overthrowing him if he continues to hide his weapons of mass destruction and deny access to U.N. inspectors.
Although he appears not to have been implicated in the Sept. 11 attacks, he could decide to give biological arms to al-Qaida in the future. He may also be progressing toward a nuclear weapons capability. But the case for overthrow needs to be compared with the costs and risks of an invasion of Iraq.
Unfortunately, most advocates of overthrowing the Iraqi regime have tended to minimize the attendant costs. For them, the rapid fall of the Taliban seemed to mark the arrival of a new form of warfare requiring only small numbers of American ground forces and promising decisive results at little cost. But there are ample grounds for thinking that war against Iraq would be much tougher.
In Afghanistan, the Taliban fought from fixed trench lines outside of cities. Similarly, during Operation Desert Storm, in 1991, Iraqi forces fought us in the desert and could not counter American airpower.
In a future war, Iraqi forces would likely take a lesson from their defeat in 1991 and fight from the cities, where civilian casualties would greatly raise the cost of airstrikes and buildings would provide disguise for weaponry and military personnel.
While many of Iraq's 425,000 active-duty troops are poorly trained and their loyalty to Hussein is questionable, his top 100,000 troops _ especially the Republican Guard and the Special Republican Guard _ are unlikely to crack quickly.
They fear retribution from Hussein or from a new regime in Iraq made up of their internal enemies more than they fear the weak Iraqi opposition and American airpower.
If there is any real hope of their deserting Hussein and handing us a victory without a fight, it will probably require the deployment of a large American invasion force on Iraq's border.
If we had to fight the Republican Guard in Baghdad, the urban combat could resemble Mogadishu, Somalia, in 1993 _ not to mention Israel's reoccupation of parts of the West Bank this year.
Small arms fired from close range would put American aircraft and troops at much greater risk than they were in Desert Storm or the Kosovo and Afghanistan conflicts. Iraq might use chemical or biological agents against our invading forces.
American military casualties could number into the thousands. Hussein may well fire SCUD missiles carrying chemical or biological warheads against Israel, Kuwait or Saudi Arabia _ or may gas Iraqis who rise against him, as he did in 1988.
Even with these factors, American forces would still win such a war and be able to install a new government. But the price would be substantial in Iraqi and American lives.
After the war, stability and democracy in Iraq would be far from guaranteed, and we might need to occupy Iraq for a decade or more.
There is a case to be made that these costs are worth it. But if so, we need Bush to tell us why. He has not yet done so.
Michael O'Hanlon and Philip H. Gordon are senior fellows at the Brookings Institution.
New York Times