Among the allegations leveled at President Bush by his critics probably the most serious is that he took the United States to war in Iraq on false pretenses. He told the American people that Saddam Hussein had a collection of dangerous weapons of mass destruction when Saddam did not.

In retrospect it is clear that the weapons did not exist, although they had in the past and Saddam had used them against his enemies. But what is also clear from captured documents now coming to light is that Bush had every reason to believe they still existed at the time he launched the military campaign in Iraq. Not only did U.S. and allied intelligence agencies assert that the weapons were there but Saddam himself played a dangerous game of convincing enemies like Iran, and his own generals, that he had such weapons, while protesting to U.N. inspectors that he did not.

While Bush may have been badly misled by his own intelligence and other sources, he did not lie. He believed, and had good reason to believe, that the weapons existed.

From thousands of official Iraqi documents captured by American forces and dozens of interviews with captured senior military and political leaders, a picture is now emerging of the world of delusion in which Saddam lived when he was in power. It is being chronicled in magazines like the Weekly Standard and a forthcoming issue of Foreign Affairs, and books like "Cobra II." Written by New York Times reporter Michael Gordon and Gen. Bernard Trainor, the book is being hailed as one of the most comprehensive accounts of the war in Iraq.

Saddam was much more concerned about an internal coup or a rebellion by dissident Shiites or even an attack by Iran, with which he had fought a long war, than he was an invasion by the United States. Though he had largely disposed of his stocks of chemical and biological weapons in the 1990s, he encouraged the Iranians to believe he might have a hidden cache of them, a strategy called "deterrence by doubt." He did not take seriously a military threat from the United States because he believed France and Russia would block the United States diplomatically at the United Nations, and that in any event the Americans had little stomach for taking heavy casualties.

The Americans, however, took seriously the probability of confronting Saddam's WMDs. When the president of Yemen, Ali Abdullah Saleh, who had close ties with Saddam, told Vice President Dick Cheney that Saddam did not want war but would use chemical weapons if attacked, Cheney did not blink. The Americans, said Cheney, would deal with them.