Since before 1991, Iraq has worked at developing nuclear, biological and chemical weapons. They have developed them (although they could not get a core nuclear device reduced to a size that was a managable payload), and in the case of the latter two, have used them. Much of this was done between 1991 and 1998 when inspections were ongoing. There is no debate in the international community as to the truth of the foregoing statements.
In September 2002, and actually prior to that as evidenced by his “axis of evil” reference in the 2002 SOU address, President Bush made a decision that Iraq, and more particularly that Saddam Hussein, posed a threat to the US because he has sponsored terrorism and his stockpile of chemical and biological weapons (and potentially nuclear) could be sold or shared with terrorist organizations that could use them against the US or other countries leading to a destabilization in the middle east and great loss of life to US citizens.
Originally, he planned to send the military and to end the problem without further discussion, but was convinced by Colin Powell (and probably Condaleeza Rice) that he shoud go to the UN. He did so, and Powell was promised by the French Foreign Minister that the French would support military action if Saddam did not comply with the mandate for immediate and unconditional disarmament. This was not true, as we now all know. By the time Iraq filed its report on December 10 (or thereabouts), everyone in the world knew that Iraq had not made a decision to disarm.
Bush would have been ready to go forward at that time, but reports were that Tony Blair needed a new resolution for political reasons. By that time, the French were completely recalcitrant, the debacle ensued, which brings us to now.
The reason we are going now is twofold. First, we have 250,000+ troops in the gulf region, and they cannot stay on alert indefinitely. Militarily, this is just not possible. Second, the weather is such that if we do not attack very soon, we will need to wait until next October or November. Even France has admitted that the presence of the US and UK forces is critical in the limited cooperation we have gotten from Saddam. We cannot afford, monetarily or militarily, to simply have that many troops sitting for an entire year while the UN debates about whether a drone should have been included in a speech, etc.
While some say Bush moved troops in too soon, there is no doubt that we would not have gotten even the limited cooperation from Iraq that we have gotten were it not for a present, viable show of force. We could not on one hand expect the process to work without a show of force, but on the other put troops in indefinitely.