This article notes:
A BBC report citing unnamed diplomatic sources, however, said U.S. contingency plans for any U.S. attack go beyond targeting atomic sites to include most of Iran's military infrastructure. With the bulk of the U.S. military tied up in Iraq and Afghanistan, it would be unrealistic to imagine any military engagement with Iran would resemble the conflict in Iraq. One might imagine that, in a confrontation with the Islamic Republic, the U.S. would want to restrict the fighting to heavy use of the Air Force, guided missiles and seaborne bombardments.
The disadvantage of trying to win a war without committing ground troops by relying almost exclusively on superior air power was demonstrated last August when Lebanese Shi'ites of Hezbollah clashed with the Israeli army. Hezbollah dug in and waited for the infantry to arrive. That is when the real fighting began. In Iran's case, the United States will certainly not commit its infantry. However, Iranian ground forces might well choose to cross the border into Iraq and confront U.S. forces there, on what is almost home turf.
I noted that a war on Iran's nuclear sites would have to be very broad to shut down Iranian counter-attack options. Indeed, I too noted that a conventional Iranian invasion isn't out of the question.
That said, I have to quibble with the comparison to the Hizbollah War. Hizbollah merely occupied southern Lebanon and was not the Lebanese government. Wrecking the infrastructure of Lebanon was not Hizbollah's problem. Wrecking the infrastructure of Iran is the mullahs' problem. And if our objective is to wreck Iran's offensive capabilities and nuclear program, a wide-ranging campaign against military, WMD, and leadership targets can surely accomplish this mission. Israel's problem was that their air campaign was too wide ranging and did not focus on Hizbollah while leaving the Lebanese people alone; and their ground campaign was too narrow and hesitant.
We certainly won't be invading Iran and attempting to pacify this large country. But I do wonder if regime change is a possibility. We've had many years to make friends inside Iran who hate the mullahs. Could we be readying a military assault that will support an uprising? I'd like to note that in that old post I figured 5 Army brigades plus Marines striking from Iraq, the Gulf, and Afghanistan could support a revolt inside Iran and complement an air campaign against nuke sites. We are adding 5 Army brigades to Iraq, 1 Army brigade to Afghanistan, and nearly a Marine brigade to Iraq. The British and NATO are adding forces to Afghanistan, too.
All of these forces are purportedly for counter-insurgency missions in Iraq and Afghanistan. But as I've long said, we can't hide moving forces to CENTCOM. We can only provide a reason for moving them to the area that masks their real purpose. And I also think that we don't really need the extra troops to win in either Iraq or Afghanistan. They are certainly useful--but not critical. And so if we needed them elsewhere the counter-insurgency missions wouldn't miss a beat.
And even if we don't plan to hit Iran with these ground forces, they would be a powerful shield should Iran lash out and invade Iraq after we launch an air campaign against Iran's leadership and nuclear facilities plus other offensive elements. With this shield in place, if Iran tries a conventional invasion, our air power will rip apart the Iranians as they try to close with our forces. Our air power savaged the Iraqis in 2003 and we've had four years to get a lot better at this.
Our options are all hard. But Iran's aren't all that hot either.
