The US really can't afford another front on the "war on terror" without some kind of draft or effective recruiting method.

If there was an attack on Iran, they probably could only do an air strike. No ground troops would be used. But the troops in Iraq will more than likely be slaughtered by Iran's army, hence it will lead to a larger conflict.

It won't be a pretty day.

Also, here is a story on the BBC showing that the evidence is a little sketchy about Iranian markings on IEDs.