In my opinion, the all-out assault will be preceded by internal guerilla uprising probably by Kurds. This will distract Saddam. He has to divert part of his elite troops to fight these guerillas. While this insurgency is in progress under the direction of CIA/SpecOps, U.S. will try to instigate defection of high ranking people or army units. Then U.S. can mount an invasion. But due to WMD, the invasion force may be spread out and move in slower pace. Anytime Saddam uses his WMD to Kurds, American troops or Israelis, U.S. will use her small nukes for retaliations. It is politically less provacative for U.S. to nuke Iraq than Israel. I know, U.S. is a great satan in Mid-East. But U.S. is still more popular than Israel. Finally, if the stalemate develops in the battlefield for some reason, U.S. will again use nukes to finish the war. U.S. cannot afford to have prolonged attrition battle Muslim extremists are so fond of waging. U.S. should not give any hopes to them. If they play madmen, they will be nuked.
Tige -- while an insurgency of the Kurds would be very good to have, both the Barzani and Talabani factions (which are more or less clan-based and fight each other intermittently) have been burnt by US indecision or withdrawal at least three times before:
I can't imagine any scenario other than a WMD attack on the US or a close ally that would lead to a US use of nuclear weapons. In fact, in many cases of WMD attack the correct responce would not be nuclear. For nukes to be worth shooting off, the provocation must be sufficient, but that's only half of the equation, the political half. The other half is military: the target must also be suitable.
So far we have faced nothing that would justify the use of nuclear arms, from a strictly military viewpoint.
d.o.l.
Criminal Number 18F