Iran. Quite a large country, larger than Iraq anyway. Very tough terrain. Much tougher than Iraq anyway. I'm not all that confident that the US Army and Marine corps would be able to execute a Blitzkrieg reminiscent of Iraq 2003. On the other hand, the collapse of the Taliban in mountainous Afghanistan was fairly quick, wasn't it? But let's face it, the Taliban were something of an irregular militia, right? And they probably didn't really have much in planning in case of a US intervention. The Iranians have probably been seriously studying how to defend themselves in case of a US invasion since 9/11, and all the more since the invasion of Iraq. What the US has in its favor is the possibility of making a two-front invasion of Iran [from Iraq and Afghanistan]. But on the other hand, it'd be a third war front for the US, how many wars can it handle?
My understanding was that the US Army is theoretically geared up for a two front war if required. Although quite what the US public would make of sending another 130 000 soldiers on a mission similiar or worse to the one in Iraq is anybody's guess. I suspect major ground operations elsewhere in the world are out until the troops are out of Iraq. Particularly since US the drift towards unilateral action in foreign policy means a coalition of any kind is unlikely, so the US would have to bear the brunt of the fighting again.
I also wouldn't use the word Blitz for the invasion of Iraq. It's not a great word, and it doesn't mean a great deal these days, but the American invasion was not WWII German style doctrine. Their blitz was about breakthrough and encirclement, but the two prongs aimed at Baghdad were all about something else. They never stopped to encircle anyone.
Although a different method, I think the plan to take Baghdad essentially conformed to what was been basic American doctrine since Grant, victory through overwhelming firepower. I thought the two armoured prongs essentially acted like tripwires. Every time they hit resistance, the troops fixed it and destroyed it with either their own organice firepower or more usually in conjunction with overwhelming fire support assets. Simple but effective, although the basic strategy was to take the head off by removing it at the nexk.
Iran, I still contend, simply isn't on. We can postulate how it might be done, but if a previously secular country like Iraq can produce the resistance it has, Iran would be far worse. You'd have to occupy it permanently, as I don't see a credible alternative. In Afghanistan and Iraq you could at least theorise there was a silent majority who would welcome regime change and embrace it. I don't think we are there with Iran, yet. There are lots of moderates, yes, but countries have a habit of uniting when under attack, and I just don't see it.
Your comments concerning the implanting of democracy etc are well made, and I fear you may well be closer to the truth than I. Pre-war there was allegedly a secular majority in Iraq. I guess we have to hope that they exist and they make themselves heard in the privacy of the ballot box away from threatening eyes. If they don't, then I don't see any easy exit strategy. Not nice to contemplate as we in the UK have tens of thousands of Soldiers on the ground as well.
Regards,
IronDuke