Yes, I understand your point. A recent article in the Christian Science Monitor compared military expenditures during WWII, Korea, Vietnam and Afghanistan/Iraq and reported that current expenditures were roughly 1% of GDP (as compared to 30% during WWII, if my memory is correct). But, then this only accounts for Afghanistan/Iraq and is not included in the $420 billion spent by the US military 2005.

Of course, the CSM article also pointed out that the cost of the current wars is being financed by borrowing. During WWII, US citizens supplied at least some of the needed savings by buying bonds. Now, we expect the Japanese and Chinese to loan us the money.

So, we might have some "fat" to burn in our campaign to rid the world of evil-doers. But in the long term, the thermodynamics are against us.