Maybe we are going in as the supporting role for another? (ie: Israel)
I think that is a real possibility. Something is up when that much fire power is deployed. Add the submarines and somebody could get their butts kicked.
This would be entirely justifiable at this point, the Iraqi government is now (finally) loudly complaining about Iranian interference. It would serve the secondary purpose of sobering up Iran regarding the consequences of not being serious about freezing its nuclear program: Message to Ahmedinajhad: We're more than ready to go the the mat if you continue on your course.
But how would the rest of the Islamo/Arab world respond? Short-term? Long-term? Do we care?