It may have already started
I saw this little item here:
9:34am CST
U.S. and British ambassadors have been summoned to Damascus regarding the claims that a missile hit a Syrian passenger bus.
There aren't any other details, like where the attack supposedly took place. What do you want to bet that bus was carrying "volunteers" towards Baghdad?
As for those Iraqis who are fighting, odds are they're people who know they'll be swinging from lamp posts if Saddam falls and the local populace gets their hands on them. Quite a few of Saddam's security forces would fall into this category.