The military does sometimes retreat. The post-Gulf War Pheonix Scorpion II was a massive sword-waving campaign. It took us a very short time to get our troops in place, and when Hussein backed down, it took months to get them out. It cost millions of dollars, but no lives were lost in fighting, and it worked.

If it doesn't work this time, it means that Hussein either doesn't think we'll follow through or he has cards he's not showing. Or perhaps this is just the "last defiant gesture" and he has a quick way out of a ravaged country, and a safe place to hide.