A retired Marine Corps colonel, Gary Anderson, writes in a The Washington Post op-ed piece that he suspects Iraq won't use chemical or biological weapons:

Anwar Sadat of Egypt reclaimed a measure of Arab pride in 1973 in a war that, while lost tactically and operationally, was fought with enough skill to regain an Arab sense of honor and pride lost in 1967. The next precept is to make the conventional phase last as long as possible and be as bloody as possible for the American-British coalition. The final sub-phase will be to attempt to turn Baghdad into an Arab Alamo and make "Remember Baghdad" a battle cry, not just for future generations but also for the rest of this war. At this point Hussein would go into hiding or exile, portraying himself as having led a glorious struggle against imperialism and vowing to continue. If he uses chemical weapons, I am wrong. There will be no sanctuary.

Anderson thinks Saddam has a long-range plan to try to wrest glory from this war that goes beyond the end of the war. By all means read the whole article -- Anderson's surmise seems plausible.