I'm scrabbling around trying to get a lot of my disorganised thoughts on the War on Terror into proper relation.
The "long war" rationale for the Iraq war is essentially a return to the Heinlein theory that in a world of nuclear weapons, potential enemies cannot be tolerated. The Middle East is a threat for the indefinite future, and therefore must be reshaped politically to remove the danger.
The problem with the theory for me is the scale of its ambition. The project aims at achieving a world, in the relevant 10-30 year timescale, where no medium-sized industrial nation capable of developing nuclear weapons will be hostile enough to be a risk of passing on the weapons to terrorists, or using them.
The strategy doesn't necessarily have to be 100% successful to be worthwhile, if a partial success would reduce the danger. But a partial success, while reducing the pool of potentially lethal enemies, might well at the same time increase the danger from those remaining in the pool, mostly by increasing their motivation to obtain nuclear weapons as a deterrent.
This is why, in the division of long-term projects I made in the previous piece, the project falls on the "hubris" side. We can be reasonably sure that having more fertile land, or having cheaper energy, 30 or 50 years in the future will be a good thing. It's difficult to say how good, but the beneficial nature of these things are robust with respect to all sorts of unpredictable developments.
It's not obvious in the same way that having a military presence in the Middle East will be a good thing. It might well be, but it easily might be a bad thing - there are well-known downsides to empire. The rationale for undertaking the project relies on a number of assumptions about political, technological and economic developments over several decades. They are not silly assumptions, but in combination they are not at all reliable.
Against that objection, there is a "desperation" argument. That says that the long-run prospects as they stand are so bad, that even if an attempt to remove the nuclear threat has a low chance of success, it is a chance worth pursuing, because it's the best chance we have.
Again, I think that's too pessimistic. I don't know how we will deal with the increasing nuclear threat over the coming decades, but as a statement of ignorance of the future, that is not particularly interesting. Something may well turn up. I'm not saying we should assume it must, but the "desperation" argument assumes that nothing will turn up, and I think that is invalid.