The Persian Gulf crisis, however it turns out, is not just about the Persian Gulf. It's also about the United States' role in the post-Cold War world. We are perhaps the only country that can now act as a global leader. But it is not preordained that we do so. Success in the Persian Gulf would breed confidence. Failure could prompt a retreat into noisy isolationism.

A good parallel is the Suez crisis, suggests political scientist William Schneider of the American Enterprise Institute. In 1956, the British invaded Egypt along with the French and Israelis to prevent Gamal Abdel Nasser from controlling the Suez Canal. The British were forced to back off by, among others, the United States. "Britain failed at Suez," says Schneider. "It was their last effort to impose world leadership."

There are vast differences between Suez in 1956 and the Persian Gulf today. We are far more powerful (both economically and militarily) than Britain in the 1950s. World opinion now seems solidly behind the United States, whereas Britain, France and Israel were relatively isolated. Still, the basic comparison is relevant. If things go badly in the Gulf, say a final goodbye to Pax Americana. No president will want to risk a similar venture in the future.

It's a myth to think our isolationist instincts vanished after World War II. They simply went into hibernation, overwhelmed by the wartime triumph and the circumstances of the time. Communism seemed to threaten U.S. interests. Americans assumed that our economic superiority would endure forever and that Europe and Japan would always eagerly accept our leadership. The crumbling of these assumptions has eroded American self-confidence and exposed an underlying isolationism.

Schneider distinguishes between two strains, "ideological" and "populist" isolationism. The ideological variety is part of a broader political philosophy. Before World War II, left-wing isolationists argued that the country had been drawn into World War I by greedy armament companies. War, in this view, sacrificed ordinary Americans for corporate profits. Right-wing isolationists admired the fascist (but orderly) regimes in Germany and Italy and wanted to stay out of war with them.

Our op-ed pages now feature new versions of these ideas. From the left, there's a strong reluctance to use U.S. military force abroad under most circumstances. This reflects a view that we often defend bad regimes: Kuwait and Saudi Arabia, we're reminded, are restrictive monarchies, not democracies. From the right comes the dissent that our vital interests aren't threatened by Iraq. Only the titanic evil of communism justified our postwar internationalism, the argument goes.

But what gives these arguments political power is their appeal to "populist" isolationism -- a vague (but widely held) sense that getting involved in foreign conflicts is "often wasteful and tragic," as Schneider puts it. Vietnam strengthened these doubts. We like to think of ourselves as self-sufficient. We see foreigners as cynical and conniving. The moralism of our foreign policy is a double-edged sword: we want either to remake foreigners in our own image or to leave them alone altogether.

We are impatient. Americans "like their wars, hot or cold, the same way they like their baseball: easily understood, brief and with a definite score at the end so it is clear who won," Cornell University historian Walter Lafeber has written. As World War II ended, American servicemen were "the most homesick troops in the world," Secretary of War Henry L. Stimson concluded. Pressures to "bring the boys home" quickly reduced the military's manpower from 12 million to 2 million. It was more a "disintegration" than a demobilization, President Truman said. You can see the same impatience now in the brief TV interviews with soldiers in the Gulf. Many say: "Hi Mom, be home soon."

Don't bet on it. Popular support for President Bush's Gulf policy is high, but this is not especially significant. We are still in the first flush of patriotism, and there has been no fighting. Even if the stalemate continues, our deployment in the Gulf isn't likely to be short. And the longer it lasts, the harder it becomes to explain. Of course, it's about oil. The trouble is that this is much more complicated than the price of oil, a few dollars one way or the other.

What's really at issue is who controls nearly two-thirds of known oil reserves -- now and well into the next century when the world's dependence on the Gulf is likely to increase. Putting this power in Saddam Hussein's hands would be an idiot's gamble. It would give him a huge potential for economic blackmail and the opportunity to create a terrifying military, including nuclear bombs, chemical and biological weapons and long-range missiles. The dangers are enormous, but they cannot be predicted precisely. They are speculative. That is the difficulty.

Everyone should grasp that we are protecting the wider interests of the world community -- not just U.S. interests -- in the Gulf. But we should not fool ourselves into thinking that we have assumed these global responsibilities merely out of habit or to polish our national prestige. The lure of isolationism, appealing though it sometimes seems, is imaginary. In a world of massive economic interdependence, we have lost that luxury, if we ever had it. Some collective interests need defending: the easy access to oil is one of them.

Leadership is the ability to persuade others to follow. President Bush needs to overcome the impatience of Americans and the unsettling timidity of our allies. The aid that he asks of Europe and Japan involves more than financial assistance. It would also be a symbolic act of support that should be followed by greater foreign troop deployments to the Gulf. American soldiers and sailors must not become the world's mercenaries. The outcome of this crisis will help shape the post-Cold War era. If we fail and fall under the shadow of isolationism, we will be moving into a more dangerous world.