Beyond everything said below, I think the main point to be made about Michael O’Hanlon’s case for higher defense spending is that it’s totally lacking in either strategic or budgetary context. Current US defense spending is extremely high by international standards:
I would say that the key to understanding the long-term strategic context is that China’s large economy is growing faster than ours, and the PRC is seeking to narrow the gap. But even as the Chinese look to us, Russia and Japan and India all need to look at China, and as Chinese defense spending ratchets up, those three other states will tend to ramp spending up as well. As I see it, no matter what we do the eventual equilibrium involves the US-China gap narrowing to a point the Chinese feel is consonant with their wealth and standing in the world, and with Russia, China, and Japan all having big enough militaries to feel safe from China. But that equilibrium can occur on any one of a number of different levels. O’Hanlon is basically urging the world to settle into a stable high equilibrium, in which real US defense spending grows at around two percent per year and the Chinese grow faster than that.
In an alternative scenario, we reach an equilibrium at a lower level. Real US defense spending stays near where it is, and real Chinese defense spending grows, but at a modest rate. That low equilibrium would leave us better off. And it would also leave the Chinese better off. And the Indians and the Russians and the Japanese and everyone else. The world could maintain roughly the same balance of power as in the high cost equilibrium, but with dramatically less wastage of resources. Now the low equilibrium would be somewhat harder to achieve as a political and diplomatic matter. But since it the low equilibrium implies a much higher standard of living for the population of the entire world, it seems to me to be worth aiming for.