The United States achieved its most important military objective in Iraq since the fall of Baghdad when it captured Saddam Hussein. President Bush rightly claimed yesterday that it was a critical milestone toward the reconstruction of Iraq. The image of Mr. Hussein, bedraggled and bearded, being humbled before Iraqi leaders, some of whom had survived his torture chambers, was a tonic of relief. One indisputable fact in the bloody and divisive saga of Iraq is that this man ranked with the world's most vicious dictators. His crimes are monstrous. Hundreds of thousands of his people were murdered or tortured at his order and some may have been brutalized by his own hands.

We hope that his arrest will reduce organized violence against American troops, although Mr. Bush himself was careful to say yesterday that hostilities are not over. We do not know how involved Mr. Hussein was in these attacks against American and allied occupation forces, or against Iraqis who cooperated with them. But the dictator's capture should offer Iraqis some relief from the lingering fear that somehow he might return to power and exact revenge on those who cooperated with the United States.

Though the Hussein regime ended with the fall of Baghdad on April 9, many frustrating puzzles remain. These include the question of what happened to Iraq's unconventional weapons programs in recent years and what was going on in that shadowed regime in the last weeks before the war, when the Iraqi leader seemed reluctant to take steps that might have stayed the president's hand.

It would be good if some of those questions could now be resolved. And it is critical that the dictator be given a fair and open trial to exact justice for his crimes, to give some solace to the people he terrorized and to give pause to other despots. The trial must be above any suspicion that it is merely an exercise in retribution or propaganda. While every effort should be made to maximize Iraqi involvement, Iraq's judicial institutions are too weak to handle the case. Although last week's creation of an Iraqi war crimes tribunal was a promising step, we would suggest this trial be conducted in Iraq under United Nations auspices by international and Iraqi judges. A tribunal picked by Americans would lack legitimacy.

Mr. Hussein's capture leaves the United States facing the same profound questions about how best to create a stable and democratic government in Iraq. The capture does not diminish the need for Washington to find ways to broaden the international nature of the occupation, and to put the nation-building efforts under the United Nations. The ultimate measure of success will be an Iraq held together by consent, not force, with its resources dedicated to development, not weapons. Iraqis will then finally be free of the malign legacy of Saddam Hussein.