The U.S.-led attack in Iraq and Kuwait last night reasserts this nation's responsibility for the maintenance of world order, a role we played in Korea and attempted to play in Vietnam. As the only country able to wield power on a global scale (the Soviet Union being, for the moment, otherwise engaged), we are, despite rhetoric to the contrary, the world's policeman.

We are not a policeman who arrests every mugger, intervenes in every dispute or mobilizes against every extortion. No nation has the capacity for such routine patrol activities. But we are -- or ought to be -- the constable who is prepared to challenge major assaults on the vital interests of the international community. That is a role we assume in addition to protecting our national interests. If this nation confines itself to using force only for its own protection, it will act as all other nations act -- with the result that threats to collective interests will never be met. It would be as if every householder fought burglars entering his own home but supported no effort to keep the streets free of organized hoodlums. In time, no one would be safe.

What is at stake in the Persian Gulf is not Kuwait, it is Saddam Hussein. President Bush says that our goal is to free Kuwait. He may say that because he believes it or because the maintenance of a delicate international coalition requires him to speak as if he believes it. But there have been scores of invasions to which we have, prudently, made no response. No armada was sent to end India's occupation of Goa; no international force tried to stand between India and Pakistan.

What is distinctive about the Gulf is that an unscrupulous dictator gives every sign of wishing to exercise hegemony over a region in which vital world interests are implicated. Those interests include a large fraction of the world's oil supply (far more important to Asia and the Third World than to us), the balance of power in an area where the Soviet Union has historic ambitions and the survival of a democratic state, Israel, which Saddam (along with many other Arab leaders) has threatened with extinction. Moreover, Saddam has made it clear that he is prepared to advance his designs by using weapons of mass destruction and sponsoring worldwide terrorist activities.

The world has no stake in restoring the emir of Kuwait to his throne. It does have a stake in retaining access to oil at market prices, in preventing a region from becoming a troubled pond in which a hostile superpower can fish, in restraining state-sponsored terrorism and in keeping weapons of mass destruction out of the hands of international bullies. Though "the world" has those interests, "the world" cannot act on them. Only the United States can act and make possible the actions of others.

If the United States is to play that role, its leaders must learn how to discuss the way in which we play it. The recent congressional debate about the use of force in the Gulf was intense, serious and (occasionally) thoughtful. But many arguments were made by proponents and critics alike that are not consistent with America's role as a superpower with responsibilities for maintaining the international system.

"Kuwait is neither strategically important nor politically attractive." That is a good argument if we are debating U.S. national interests. It is not a good argument if we are debating U.S. international responsibilities. To protect vital world interests, it will often be necessary to threaten or even use force on behalf of unattractive nations. Policemen cannot maintain order only by arresting gangsters when they happen to have terrorized nice people. What is at issue is the importance of the gangster, not the innocence of the victim.

"Other countries are not paying their fair share." Indeed not, nor will they ever pay their fair share. Economists call this the "free rider problem": no one has an incentive to pay for a benefit that he will obtain for free. What is astonishing in the Gulf is that we have obtained as much financial support as we have. Absent an international tax system for assessing the costs of international policing, we face a simple choice: either vital world interests will go unprotected, or we will do it for free. Some members of Congress have spoken as if we could have it both ways. We cannot.

"Every alternative to war should be exhausted before we resort to war." That is correct in theory, but international diplomacy is not an exercise in theory, it is a high-stakes poker game in which the credibility of one's bets is as important as the value of the cards one holds. When the stakes are high, every tactic -- negotiations, threats, sanctions -- depend on the other side's belief that you can place in grave jeopardy his vital interests. If you tell your adversary in advance that you are uncertain whether you will use force, you are playing poker with your hole card exposed. You may win a few hands that way, but no big pots.

"We should only use low-cost, surgical military force." One senator said he would support air strikes but not infantry advances. There are few cases in military history of air power playing a decisive role; there are no cases of it playing that role alone. Perhaps air strikes combined with sanctions will, in the case of Iraq, prove the exception. But even that chance vanishes if we announce in advance that, provided you are willing to hunker down and endure our bombing raids, you have nothing more to fear from us. War is not surgery, it is armed struggled.

"The American soldiers who will be killed will be disproportionately poor or black." Yes. But consider the argument we would be hearing if we had a conscripted rather than a volunteer army. "These young men didn't volunteer for this war, they are forced to fight it! We cannot send the flower of our youth {by which is meant upper-middle-class college students} to die in some far-off place." And of course, the college campuses would be aflame with antiwar (actually, anti-draft) protests. Soldiers die in war. There is no kind of soldier whose death is morally superior to the death of any other kind.

"We shouldn't spill blood to knock a dime off the price of oil." That is a bit like saying we shouldn't have invaded Normandy in 1943 to knock a quarter off the price of claret. The short-term effect on commodity prices is the least of the harm done by international gangsters. But when the commodity is oil, price is a more serious matter than when it is wine. Almost every underdeveloped nation needs more energy than it now has. Bangladesh, Zambia and Bolivia will not get this energy from photovoltaic cells. They will get it from fossil fuels. America can and should conserve such fuels, but we can do so with only minimal cost to our standard of living. As the oil embargo of 1973-1974 revealed, it is the poor nations that suffer most from high prices.

"Things can't be so serious if Germany and Japan are sitting on the sidelines." Germany and Japan sit on the sidelines not only because of the free rider problem but because they face powerful political and constitutional constraints against sending military forces outside their borders. As you may recall, we fought the Second World War to persuade them to adopt such constraints. They have.

In sum, the proper topic of debate is the magnitude of the threat posed by an aggressive nation. That is not easily determined, since any such estimate is of necessity a prediction. But unless we wish to abandon our role as the principal guarantor of the vital conditions of international order, it is irrational to spend much time deploring the unseemly qualities of the victim, squinting at the allocation of costs among coalition partners, insisting that our diplomatic hole card always be kept face up or sneering at oil as if it were a luxury that people in Bethesda ought to learn to do without.

There is, of course, a peace party in Congress. Found on both sides of the aisle but mostly on the left wing of the Democratic Party, it rejects the view of this country as an international policeman or even as a superpower. Such is the strength of this group that it may be able to make pacifism, in fact if not in name, a precondition for receiving the Democratic nomination for the presidency. I think it important for this group to make plain its views and in particular to answer directly these questions:

What, exactly, are the circumstances, short of the invasion of the United States, for which the use, or the credibly threatened use, of American military force is appropriate? Are you willing to trust entirely to the self-interest of other nations to protect against the rise of international gangsterism?

The writer is Collins professor of management and political science at UCLA.