Good post.

Also, historically, evil barbarians regularly fall prey to some irrational doctrine or personal paranoia that wastes their resources (sacrifice to the gods, kill all your Jews, kill everybody in the Ukraine, have a cultural revolution).

We in the US probably have a peculiar attitude on the rationality of war because we've never, with the possible exception of the War of 1812, fought in a war that was very rational (in terms of the benefits for us). The Revolutionary war? The war with Mexico? The Civil War? The Spanish-American War? WWI? WWII? Korea? Vietnam? Iraq? None of them make sense in terms of self-interest.

(Disclaimer: I'm a little drunk at the moment.)