Iranian invasion of Iraq?

[phillies]

The Iranians are going to invade with four battalions?  We couldn't take Fallujah back with that, though two of them were in reserve.  The Iraqis can handle four Iranian battalions by themselves, with the forces they have right now.

Let me propose a rational explanation, namely the Iranians expect that after we do not leave and install a new set of puppets that matters in Iraq will become less pleasant, and that they may have to cope with large numbers of refugees (or, this being a desert, rescue large numbers of refugees).