[makomk]

We knew that Iraq had WMDs because a number of western countries sold them some a few decades ago to drop on Iran on our behalf. That's not a secret, and if I recall correctly they were tightly secured and probably degraded to the point of ineffectiveness by that point. The claim that justified invasion was that they had new chemical weapons programs, and that seems to be categorically untrue and without evidence.

[AnimalMuppet]

It's not that simple. Saddam was trying to make it look to his neighbors (especially Iran) that he had WMDs. Recall that this is very shortly after the end of the decade-long Iran-Iraq war. He wanted to be very convincing, so as to make his neighbors unwilling to oppose him.

At the same time, he was telling the US, "Who, me? I don't have any WMDs." Which made him look like a two-faced liar. The "evidence" that he wanted his neighbors to see convinced Washington.