"...one suspects that Bush just wanted his own launching pad for Iran from his base in Iraq..."
You can't drive on Tehran with 23 unopposed divisions on your left flank.
Then too, Iraq had value in the following equation:
2 towers = 2 flags
The only real question left is whether Syria will cave after Tehran falls, or will they force us to implement regime change there as well. My money says they cave, and that Nayaf and his followers in SA hasten to follow them.
I am more interested in the shake and bake stage, LONG before ground troops go in.