Suppose some time in the near future the US government was considering an invasion of Iran ,say, in order to prevent it from acquiring nuclear weapons. Is a successful invasion feasible?
IMO in any practical sense it is not feasible. I think the US would probably destroy the Iranian airforce and any concentrated Iranian formations quite quickly. However the Iranians will probably wage a large-scale guerrila war to defend their country. Even if the US were to capture the major cities I think the level of casualties would be unacceptably high and the country nearly impossible to occupy for the following reasons:
1)Iran is larger than Iraq and has a lot more people.
2)Its terrain is a lot more mountaneous than Iraq and so more suitable for guerilla warfare.
3)Iran has the advantage of examining the recent war to see what works and what doesn’t work against the US military. You can bet their planners are carefully examing the guerilla tactics used both during and after the main war and planning to use them on a far larger scale if the US attacked.
4)Iran is not under UN sanctions and they can stock up on those weapons that will be most useful to them like night-vision goggles and anti-tank missiles. They will be a lot better equipped than the Iraquis.
It’s hard to see where the launching pad would be. The logical country would obviously be Iraq. but it’s hard to see any Iraqi government allowing a US invasion of Iran from Iraq. If the US tried it anyway it would probably lead to a full-scale Shia revolt in Iraq.
The UK would probably not join any such war and the US will be even more short of troops than in Iraq today.