America has gone to war by formal congressional declaration twice in this century, first in 1917 and again in 1941. Those were the "good" wars -- World Wars I and II -- as they are still popularly styled. They were "good" in the sense that they represented just causes around which a clear national consensus had formed, as opposed to "good" in the romantic glory-of-combat notion still popularized in contemporary television dramas and "Rambo" films.

Twice in this "American Century," as the jingoes have proclaimed it to be, the United States has fought major, albeit undeclared, unpopular wars in Korea and Vietnam. Numerous times over those decades, Americans have engaged in combat operations against assorted guerrillas, insurgents, terrorists or dictators. Also, most notably, they have fought and won a historic Cold War that dominated American life and defined world affairs for more than two generations.

But never has America been on the verge of a major war in circumstances quite like those today. There's neither great support for or against it, nor agreement on why it's necessary. Yet, pervasive ambiguity and anxiety aside, there is no doubt that the American people will back war if it comes.

This prospective war did not begin with a sudden, unexpected attack on American forces, as at Pearl Harbor or across the 38th parallel separating North and South Korea. It did not creep upon the nation inch by inch, year by year, as did the Vietnam morass. Nor, presidential rhetoric notwithstanding, did it start because America faced the threat of a Hitler who sought to rule the world by conquest and had the power to do so.

This also would be, on its face, a most unlikely war. Never in history has a nation possessed such overwhelming military and technological prowess as the United States now enjoys. Despite its economic woes, the American nation of 250 million people stands as the world's sole remaining superpower and, by any international standard, continues to be rich beyond measure. Arrayed against it is a Middle Eastern state of about 16 million people in grave economic straits and further weakened internally by the legacy of an eight-year war with Iran that ended with a cease-fire, loss of half a million Iraqi lives and virtually no resolution.

There's no question -- none -- about the military outcome of a U.S.-Iraqi war. Iraq cannot possibly win a battlefield victory. But the United States almost certainly would incur heavy losses and face further serious problems in the turbulent Middle East long after combat ended.

For these reasons, and others, I was among those who believed that war would be averted at the last minute. That belief was dashed in chilling, almost brutal fashion by the extraordinary events of Wednesday.

Not since the Cuban missile crisis 29 years ago had the entire world been so wired to its collective television sets as it awaited word on war or peace. With his somber, sorrowful statement in Geneva that "regretfully, ladies and gentlemen, I heard nothing today . . . that suggested any Iraqi flexibility," Secretary of State James A. Baker III turned fresh hopes into instant despair.

There was much talk by Baker, and later by Iraqi Foreign Minister Tariq Aziz, about which side had miscalculated most seriously the intent, or will, of the other. Of course, both made serious miscalculations. When all was said, however, no one could doubt that the prospect of war had increased dramatically.

But war is not inevitable, even now. Sen. Sam Nunn (D-Ga.), a consistent voice of tempered reason on the Persian Gulf crisis, says he still believes that President Bush's original strategy of economic sanctions and patience, backed by overpowering military force and willingness to use it, can prevail.

Writing on The Washington Post's opposite-editorial page yesterday, Nunn noted: "Iraq is unique in its vulnerability to economic embargo. The international blockade has succeeded in cutting off almost 100 percent of Iraq's exports (mostly oil), stopped over 90 percent of all imports and reduced its GNP by an estimated 50 percent. Over time, experts estimate the Iraqi GNP would be down by about 70 percent, the country would be an economic basket case and Saddam Hussein may be in jeopardy with his own people."

He also cited CIA Director William H. Webster's testimony that sanctions "will increasingly weaken Iraq's military power through shortages of spare parts and munitions and equipment breakdowns" as further reason to stick with the sanctions. "War," he said, "should be a last resort."

Put me down on Nunn's side, but put me down too as among those now more pessimistic about the prospects for peace.