Since the war in Iraq ended, supporters and critics alike have reached a near-consensus that the main reason given for the U.S.-led operation -- the threat posed by Iraq's possession of weapons of mass destruction -- was baseless. U.S. President George Bush and British Prime Minister Tony Blair insist that it's just a matter of time before those weapons are found, retroactively justifying the war, but to no avail.

Judging by polls, letters to editors and online exchanges, the general public thinks that the facts we have now justify nothing but skepticism. Teams of U.N. inspectors failed to find WMD in Iraq in the months before the war. Occupying forces have failed to find them since the war. Therefore, people conclude, Iraq did not pose -- in fact, could not have posed -- the threat of which it was accused. Is that conclusion warranted?

There have been varied responses to the case of the missing WMD. Critics say it proves the so-called preemptive war was indefensible all along (how can you preempt the nonexistent?) The war's supporters, meanwhile, are divided. A few may have lost faith in the righteousness of the cause. More, though, have merely changed their grounds for supporting it. The war was justified, the logic now goes, because of the domestic horrors perpetrated by the Hussein regime. The advertised "war of preemption" quickly became a "war of liberation" as the weeks rolled by, and what emerged from the desert landscape was not weapons of mass destruction but mass graves.

The one response missing, until recently, was any authoritative challenge to the assumption that the absence of WMD necessarily means that pre-invasion Iraq no longer posed a threat to anyone but its own people. It is an assumption to which many reasonable people still subscribe. But the gap was filled last week by a cogently reasoned article by Rolf Ekeus, ex-chairman of the U.N. Special Commission (UNSCOM) on Iraq, published in the Washington Post on June 29. For many, the former chief weapons inspector was the first to try to explain, in laymen's terms, why Iraq really did pose "a major threat to international peace and security" and why what he calls the "rather bizarre" focus on missing weapons represents a "distortion and trivialization" of that threat.

Why bizarre? Because, Mr. Ekeus says, there's more to a chemical or biological weapons program than rusting drums and pieces of munitions. Certainly, the Iraqis possessed -- and used -- warfare agents in their 1980-88 war against Iran. But one thing they learned from the experience was that biological and chemical agents, especially nerve agents, deteriorated after just a couple of weeks of storage because Iraqi scientists lacked access to sufficiently high-quality equipment.

As a result, Mr. Ekeus writes, "the Iraqi policy after the Gulf War (1991) was to halt all production of warfare agents and to focus on design and engineering, with the purpose of activating production and shipping of warfare agents and munitions directly to the battlefields in the event of war. . . . Such work could be blended into ordinary civilian production facilities and activities, e.g., for agricultural purposes."

Mr. Ekeus' conclusion strikes a note not yet heard in the ongoing debate about phantom weapons. "This combination of researchers, engineers, know-how, precursors, batch-production techniques and testing is what constituted Iraq's chemical threat -- its chemical weapon." The same, he says, is true of its biological warfare program, which remains just that -- a program, an abstract capability, rather than a stash of stored agents of "doubtful quality."

As to the precise nature of the threat this posed, Mr. Ekeus scoffs at the idea that Iraq's WMD capabilities were ever directed at the United States or even Israel, or that its failure to use them in the recent war meant that it didn't possess the capability. Iraq's WMD program, he argues, was developed in the contexts of the regional rivalry with Iran and the suppression of its own minorities: "The fact that Iraq . . . did not counter the coalition forces, now even better trained and equipped than last time, with chemical weapons, should not have come as a surprise."

The real threat posed by Iraq was twofold: the possibility that it might use WMD on the battlefield against a poorly equipped and ill-trained neighbor; and the chance that Iraqi weapons specialists -- distinct from the Iraqi regime -- might have signed on to help terrorist networks such as al-Qaeda. The latter, he reminds us, is still a danger.

Mr. Ekeus overall pulls no punches: "Letting [Saddam] Hussein remain in power with his chemical and biological weapons capability . . . would have been to tolerate a continuing destabilizing arms race in the Gulf." WMD may never be found in Iraq, he concedes. But WMD was and remains the war's justification.