To those who study the ethics of war, Air Force Gen. Michael J. Dugan's declaration that the United States has planned a massive bombing campaign "whose cutting edge would be in downtown Baghdad" underscored the unexamined moral implications of taking military action against Saddam Hussein.

Defense Secretary Richard B. Cheney promptly fired Dugan for his outspoken interview with three reporters, but Cheney did not dispute the accuracy of what Dugan had said. The secretary said the Air Force chief of staff had stepped out of line by speaking speculatively about "operational details."

"I'm concerned that there has never been an exact repudiation of that statement," said the Rev. J. Bryan Hehir, a professor of ethics and international politics at Georgetown University. "They've just said that he was not wise in saying it."

The United States has options far short of sending bombers after Iraqi President Saddam Hussein and his mistress -- another of Dugan's suggestions -- that also raise ethical questions. But the threats by generals and public officials including Dugan to unleash U.S. air power against Iraq -- while usually accompanied by a careful distinction that targets would be military rather than civilian -- have led some ethicists to question whether the ramifications of using U.S. military forces against Iraq have been fully considered.

"We're going to give them the most violent three to five minutes they've ever seen," said Marine Maj. Gen. Royal N. Moore, expressing the Pentagon's desire to use maximum force if there is war. And Rep. Les Aspin (D-Wis.), chairman of the House Armed Services Committee, commenting on the military's opposition to gradual escalation, said, "Once you get air superiority, they will want to flatten Baghdad."

Such statements worry people such as George Weigel, president of the Ethics and Public Policy Center here, because if there is one generally accepted position among the ethics experts, it is that targeting civilian populations is the most morally alarming approach to war possible.

"Heavy bombing of Baghdad doesn't make any political sense, military sense or moral sense," said Weigel, reflecting a widely held view among students of war ethics -- even those who, like Weigel, support President Bush's Middle East policies.

And it raises a broader question to Weigel and his colleagues of whether in fact some ways of waging war are more moral than others.

The notion that one can apply ethical categories to mass violence strikes many as problematic or even absurd. "In warfare, if truth is the first casualty, moral principles aren't very far behind," said Richard John Neuhaus, director of the Institute on Religion and Public Life in New York.

The seeming futility of the quest for "war ethics" drives many to a principled opposition to all wars. "My view is that war is bad and unjust war is even worse," said Stanley Hauerwas, a pacifist and professor of theological ethics at the Duke Divinity School.

Others are brought to the hard-edged view that once war begins, rules are doomed to be broken. "The attempt to fight a moral war is a hugely ambitious enterprise," said Patrick J. Glynn, a resident scholar at the American Enterprise Institute. Glynn cited an axiom of the military strategist Karl van Clausewitz to the effect that "war is such a dangerous business that the mistakes that come from kindness are the very worst."

But those who seek moral limits on warfare argue that it is precisely because war is so brutalizing that constraints must be accepted ahead of time.

"We tend to sacrifice constraints when we are convinced of the moral righteousness -- or even moral holiness -- of our cause," said James Childress, a professor of religious studies at the University of Virginia and the author of "Moral Responsibility in Conflicts." Moral limits are best agreed upon, he said, before combatants get engulfed in their righteousness.

Thus, nations have been making rules and judgments about war for centuries. Even Adolf Hitler, who was gassed as a soldier during World War I, abided by international conventions against gas warfare.

William V. O'Brien, a professor of government at Georgetown, noted that the Hague Convention of 1907 set rules on how land warfare could be conducted, and that the Geneva Convention of 1949 established rules on how the wounded, the sick, prisoners of war and civilians under occupation should be treated.

And, while it was not the product of a formal treaty, "the Nuremberg principle," established in the Nazi war crime trials after World War II, found that soldiers were obligated to disobey the orders of their superiors if they were commanded to commit war crimes or "crimes against humanity" such as genocide.

In the West, much of the debate over the morality of warfare has been informed by "just war" theories developed initially by Augustine, codified by Thomas Aquinas in the Middle Ages and elaborated upon ever since. Just war theory was an attempt to square basic biblical injunctions against murder -- "Thou shalt not kill" -- with the seeming inevitability of armed conflicts between states, nations and empires.

Just war theory, said Weigel, "grew out of an effort to put effective moral constraints on violence while holding out that the last resort to violence can, under certain circumstances, serve the cause of peace and justice." While its roots are largely Christian, there are analogues in Jewish, Islamic and secular theorizing. John Kelsay, who teaches ethics and Islamic studies at Florida State University, said the formal structure of Islamic just war theory "is strikingly similar" to its Christian counterpart, though "the answers are sometimes different."

Just war theory is essentially an attempt to clearly restrict moral justifications for wars. In its basic form, the theory holds that the cause being fought for must be just, that the intentions of those fighting must be right -- those inflicting violence cannot do so because they enjoy it -- and that the authority of those waging war must be proper.

In addition, war should be pursued only as a last resort, and those waging war must have reconciliation with their enemies as their ultimate goal.

Just war theorists have also developed two central concepts for judging the morality of particular actions. "Proportionality" holds that no more force should used than is necessary for achieving an end. The concept of "discrimination" holds that there should be no deliberate targeting of noncombatants.

Not surprisingly, just war theories are open to a broad range of conflicting interpretations and applications -- notably in the current crisis in the Persian Gulf. Modern weaponry has also complicated the theorizing. On the one hand, Weigel noted that modern weapons, especially nuclear weapons, have unparalleled destructive power, which makes them morally problematic on their face. On the other hand, targeting has become so much more sophisticated that it is now much easier to avoid "collateral damage" to civilian populations.

But there are also difficulties at the heart of just war theory. Weigel, for example, noted that "proportionality bangs up against the reality that the overwhelming application of force works and shortens wars. Incrementalism causes all sorts of problems -- i.e., Vietnam."

Glynn, for one, believes that if the United States goes to war with Iraq, the best course -- morally and practically -- would be to apply overwhelming force quickly. "We can't allow an overscrupulous moral calculus to restrict our decisions in the opening phases of an air campaign," Glynn said. "The first 48 hours of that campaign will determine whether the war is measured in days or in months."

The most basic just war principle is that civilian populations should be immune from massive attack. This means, said James T. Johnson, university director of international programs at Rutgers University, that "you can hit Hans the Worker at the ball-bearing factory when he is working in the factory making ball bearings, but you cannot bomb Hans's home and kill his wife while she is making Hans's lunch."

Obliteration bombing of civilians, said Michael Walzer, a political theorist at the Institute for Advanced Study at Princeton and the author of "Just and Unjust Wars," is "the equivalent of terrorism on a large scale -- you're killing innocent people to affect the behavior of their government."

The Strategic Bombing Study after World War II suggested that mass bombing of civilians by both the Allies and the Axis had little effect -- and may even have been counterproductive. The better bet, both morally and practically, Weigel said, is to attack military targets -- in Saddam's case this would notably include chemical and nuclear weapons facilities. "This is a happy case of what is more morally satisfactory also being more effective," he said.

The most fervently debated use of military force on civilians was of course the U.S. decision to drop atomic bombs on Hiroshima and Nagasaki in an effort to break Japan's will and end World War II. The arguments still rage between those who contend that dropping the bombs shortened the war and reduced casualties, and those who insist that such a calculus -- even if true -- simply cannot justify the amount of death and suffering involved in the attacks.

If Dugan raised a storm with talk of bombing Baghdad, he also provoked controversy by suggesting that Saddam himself would be the key target in a bombing campaign -- a military strategy known as "decapitation."

Johnson argued that there was a certain irony to Dugan's comments because, while his suggestion to target Baghdad was morally unacceptable, "decapitation" was "a logical extention of proportionality and discrimination" and thus far more morally defensible.

In search of alternatives to military action, opponents of war have argued that the economic embargo should be given time to work. But the embargo itself, in the eyes of ethics experts, raises many moral problems of its own. "With a blockade, the weakest suffer first and most," said Weigel. "The political and military leadership certainly won't suffer most. Why is that a more morally satisfactory strategy than military action?"

But Jim Wallis, editor of Sojourners, a left-of-center Christian magazine, countered that an economic embargo is certainly more moral than war, provided that the embargo did not restrict the delivery of food and medical supplies.

Advocates of nonviolence such as Wallis and Hauerwas argue that those who engage in just war theorizing on behalf of action against Saddam are ignoring more fundamental questions, such as whether U.S. goals in the Middle East are worth a war.

In the end, however, many ethicists say Dugan may have done the nation a moral service -- by opening up a broad moral debate on U.S. options in the Middle East before hostilities there reach war level.

"In this case we have some lead time," Walzer said, "and I think it's important that ideas like carpet bombing Baghdad get discussed ahead of time, so it can't happen."