Veterans, more than anyone else, understand the need for vigilance. It is an undeniable truth that when a brutal dictator possesses chemical and biological weapons, and is in pursuit of nuclear weapons, he poses a global threat to peace and security.

But would President Bush's war against Iraq qualify as a just war? The question is not frivolous. During America's Afghanistan campaign to oust the Taliban, Defense Secretary Don Rumsfeld met with theologians to ensure that U.S. actions were in conformity with "just war" principles.

The "just war" doctrine is a Western idea-actually, an idea that Western civilization got from Christianity. "Just war" theory does not condemn all war, in the way that pacifism does, but it does place strict moral limits on the reasons that justify going to war, and on how the war is conducted.

First, the war must be undertaken as a last resort, when other alternatives have been exhausted. To his credit, President Bush has not rushed into war. He has worked with the United Nations and the international community to find a diplomatic solution. The U.N. resolution gives Saddam Hussein a chance to voluntarily relinquish his weapons of mass destruction, and avert war. Only if Hussein refuses will the United States and its allies resort to military force.

Second, under "just war" theory it is forbidden to target civilians. This does not mean that civilians are not killed in just wars. But they should not be killed deliberately. What this means is that nations should take all reasonable measures to minimize civilian casualties. Only soldiers and military facilities should be targeted. The United States was scrupulous in following this rule in the Afghanistan war, as in the Gulf War of a decade ago. There is no reason to believe that Iraq will be any different.

Third, America's actions in a "just war" must be proportionate to the danger that is being averted, and have a reasonable probability of success. As in edict about targeting civilians, these criteria are more applicable to the conduct or war than to the question of whether the initiation of war is justified.

Once again, the United States is likely to use whatever force is necessary to get rid of Saddam Hussein, but it is not going to seek to use disproportionate or excessive force against the Iraqi people. There is no question, for instance, of America using nuclear weapons. Moreover, America is unlikely to initiate war without a high degree of certainly that it will result in Hussein's ouster. Although there is no guarantee of what will follow, Hussein's is almost certain to be replaced with one that is less repressive and more humane.

The most difficult criteria for America to satisfy is the final one which says that a just war has to be defensive. Traditionally, this means that a nation must be first attacked. This criterion would seem to forbid preventive or pre-emptive action against Iraq.

But in the new atmosphere post 9-11, and in a world where evil regimes seek weapons of mass destruction, it is not always possible to wait until after an attack in order to respond. The vaporization of Tel Aviv or Chicago is not a price that can or should be paid. In other words, a nation may under extreme circumstances be justified in using force to prevent a global catastrophe. If Hitler could have been stopped before 1939, would that not have been a just action? So, too, a war to remove Saddam Hussein from power would satisfy the requirements of a "just war."