With no weapons of mass destruction as yet found in Iraq, the political criticism directed against President Bush and British Prime Minister Tony Blair is mounting. Before the war, the two leaders publicly declared that the Iraqi regime had not only procured and produced such weapons but still retained them with the intention to use them. This was considered a good reason for a military operation against Iraq -- an outright casus belli.

A United Nations inspection team, before the war, and the U.S. military, after the war, have been searching Iraq and have not come up with anything that can remotely be called weapons of mass destruction. Is it now time to join the game of blaming Bush and Blair for an illegitimate or illegal war? Let us first consider some facts in a complicated picture.

Chemical weapons were used by Iraq in its war against Iran (1980-88). Arguably that use had a decisive effect on the outcome: It saved Iraq from being overwhelmed by a much larger Iranian army. Furthermore, Iraq made use of chemical bombs in air raids against the Kurdish civilian population in northern Iraq. Nerve gases, such as sarin, and mustard gas immediately and painfully killed many thousands of civilians. More than 100,000 later died or were crippled by the aftereffects.

These reminders illustrate that Iraq's acquisition and use of chemical weapons were carried out in pursuit of two strategic goals, namely to halt Iran's possible expansion of its sphere of influence in the Persian Gulf region and to suppress internal opposition. The war started by Iraq in 1980 was directed against its historical enemy, Iran. In strategic terms and over generations, Iraq/Mesopotamia had been positioned as a gatekeeper of the Arab nation against repeated Persian expansion westward, a threat that had become acute with the Islamic revolution in Iran in 1979. All the emirates and states in the gulf region, ruled by Arabs of traditionalist Sunni Muslim orientation, considered Persian nationalism and expansionism a constant problem, especially after Iran's Shiite revolution.

For Saddam Hussein, the self-styled, self-promoted defender of the Arab nation, "the Iranian beasts," to quote Tariq Aziz in a conversation with me -- not the United States or Israel -- were the eternal enemy of Iraq. With its population of more than 64 million, Iran constituted a challenge that Iraq, with its 24 million inhabitants, could not match with conventional military means. By using chemical weapons to gas and kill the "human waves" of young, poorly protected Iranian attack forces, the Iraqi army repeatedly saved itself from being overwhelmed. And thus it became conventional wisdom, nourished by the Iraqi leadership, that only nonconventional weapons could guarantee that Iraq would prevail in an armed conflict with Iran.

Regarding biological weapons, the U.N. inspection team, UNSCOM, managed after four years of investigation to confirm the existence in Iraq of a major secret biological weapons program. This led in August 1995 to the defection from Iraq of Saddam Hussein's son-in-law Hussein Kamal, director of Iraq's WMD programs. During UNSCOM's debriefings in Iraq after the defection, Iraqi biological weapons scientists, able to speak slightly more openly than normally, explained that their secret work mainly was on assignments to find means for warfare against the Iranians.

Regarding the nuclear weapons projects, the Iraqi authorities defended their systematic violation of Iraq's obligations under the nuclear Non-Proliferation Treaty with the proposition that Iran, likewise a party to the treaty, was active in developing its own nuclear weapons. Iraq's obsession with Iran was illustrated by its air attack in 1983 on the Iranian nuclear reactors at Busher.

Even the quite remarkable missile developments in Iraq were related to Iran. Iraq succeeded in modifying and re-engineering many hundreds of the more than 800 Scud missiles bought from the Soviet Union -- increasing their range of 200-300 kilometers to 500-600 kilometers, sufficient to reach Tehran.

In sum, all four components of Iraq's prohibited and secret WMD program were motivated and inspired by its structural enmity and rivalry with Iran. Thus, during the Gulf War in 1991, Iraq did not use its readily available chemical weapons, stored in considerable quantities in southern Iraq, against the U.S.-led forces. The Iraqi leadership made clear to me that there would have been no military sense in using chemical weapons on such a fast-developing battlefield, where the enemy was highly mobile, well trained and well equipped for chemical warfare. In addition, the Iraqi willingness to use chemical weapons had been tempered by U.S. Secretary of State James Baker's promise to Iraqi Foreign Minister Tariq Aziz that such a contingency would change the U.S. war aim from the liberation of Kuwait to regime change in Iraq.

The fact that Iraq in the recent war 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 chemical weapons, like the other WMD, had been developed with another enemy in mind. But a big question remains about the puzzling absence of chemical weapons in Iraq. Detractors of Bush and Blair have tried to make political capital of the presumed discrepancy between the top-level assurances about Iraq's possession of chemical weapons (and other WMD) and the inability of invading forces to find such stocks. The criticism is a distortion and trivialization of a major threat to international peace and security.

During its war against Iran, Iraq found that chemical warfare agents, especially nerve agents such as sarin, soman, tabun and later VX, deteriorated after just a couple of weeks' storage in drums or in filled chemical warfare munitions. The reason was that the Iraqi chemists, lacking access to high-quality laboratory and production equipment, were unable to make the agents pure enough. (UNSCOM found in 1991 that the large quantities of nerve agents discovered in storage in Iraq had lost most of their lethal property and were not suitable for warfare.)

Thus the Iraqi policy after the Gulf War 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 battlefield in the event of war. Many hundreds of chemical engineers and production and process engineers worked to develop nerve agents, especially VX, with the primary task being to stabilize the warfare agents in order to optimize a lasting lethal property. Such work could be blended into ordinary civilian production facilities and activities, e.g., for agricultural purposes, where batches of nerve agents could be produced during short interruptions of the production of ordinary chemicals.

This combination of researchers, engineers, know-how, precursors, batch production techniques and testing is what constituted Iraq's chemical threat -- its chemical weapon. The rather bizarre political focus on the search for rusting drums and pieces of munitions containing low-quality chemicals has tended to distort the important question of WMD in Iraq and exposed the American and British administrations to unjustified criticism.

The real chemical warfare threat from Iraq has had two components. One has been the capability to bring potent chemical agents to the battlefield to be used against a poorly equipped and poorly trained enemy. The other is the chance that Iraqi chemical weapons specialists would sign up with terrorist networks such as al Qaeda -- with which they are likely to have far more affinity than do the unemployed Russian scientists the United States worries about.

In this context the remnants of Iraq's biological weapons program, and specifically its now-unemployed specialists, constitute a potential threat of much the same magnitude. While biological weapons are not easily adapted for battlefield use, they are potentially the more devastating as a means for massive terrorist onslaught on civilian targets.

As with chemical weapons, Iraq's policy on biological weapons was to develop and improve the quality of the warfare agents. It is possible that Iraq, in spite of its denials, retained some anthrax in storage. But it could be more problematic and dangerous if Iraq secretly maintained a research and development capability, as well as a production capability, run by the biologists involved in its earlier programs. Again, such a complete program would in itself constitute a more important biological weapon than some stored agents of doubtful quality.

It is understandable that the U.N. inspectors and even more, the military search teams, have had difculty penetrating the sophisticated, well-rehearsedand protected WMD program in Iraq. The task was made infinitely more challenging by the fact that Iraq was, and indeed still is, a "republic of fear." Through my indirect contact with some senior Iraqi weapons scientists, I have been given to understand that the reign of terror is still in place.

Outsiders who have not dealt with Iraq cannot easily understand the extent to which the terror of the Hussein years has penetrated that unhappy nation. As long as Hussein and his sons are not apprehended or proven dead, few if any of those involved in the weapons program will provide information on their activities. The risk of terrible revenge against oneself or one's family is simply too great. The first point on a WMD agenda must be to create a safe environment free from the remnants of terror.

The chemical and biological warfare structures in Iraq constitute formidable international threats through potential links to international terrorism. Before the war these structures were also major threats against Iran and internally against Iraq's own Kurdish and Shiite populations, as well as Israel.

The Iraqi nuclear weapons projects lacked access to fissile material but were advanced with regard to weapon design. Here again, competition with Iran was a driving factor. Iran, as a major beneficiary of the fall of Hussein, has now been given an excellent opportunity to rethink its own nuclear weapons program and its other WMD activities.

The door is now open for diplomatic initiatives to remake the region into a WMD-free area and to shape a structure in the Persian Gulf of stability and security. Moreover, the defeat of the Hussein regime, a deadly opponent to peace between Israelis and Palestinians, has opened the door to a realistic and re-energized peace process in the Middle East.

This is enough to justify the international military intervention undertaken by the United States and Britain. To accept the alternative -- letting Hussein remain in power with his chemical and biological weapons capability -- would have been to tolerate a continuing destabilizing arms race in the gulf, including future nuclearization of the region, threats to the world's energy supplies, leakage of WMD technology and expertise to terrorist networks, systematic sabotage of efforts to create and sustain a process of peace between the Israelis and the Palestinians and the continued terrorizing of the Iraqi people.

The writer was executive chairman of the United Nations Special Commission (UNSCOM) on Iraq from 1991 to 1997. A former Swedish ambassador to the United States, he is now chairman of the Stockholm International Peace Research Institute.