Steve Sailer looks for ways to trim the costs of empire, and searches for the logic behind American troop deployments:
For example, almost 20 years after the fall of the Berlin Wall, we have 56,200 military personnel based in Germany. Doing what, exactly? Protecting Germany from whom? France? Poland?
We have 33,000 troops in Japan, another expensive country, and 28,000 in South Korea. ...
So, what's the war-fighting reason for deploying only moderately large numbers of troops overseas? It sounds like we have, in the unlikely event of a central European war, not enough troops in Germany to win, but, instead, just enough troops to suffer the worst defeat in American history.
I believe that it was Thomas Schelling who argued that putting 10,000 troops in W. Berlin would be enough of a deterrent to prevent a Soviet invasion of W. Germany. Why? Certainly not because they could actually repel an invasion, but because a "moderately large number of troops" sent a credible signal that we were committed. If the Soviets invaded, we'd have the rest of the US Armed Forces in the theater within a week. Staffing bases with a skeleton crew (or out-sourcing maintenance to the local population, as Sailer suggests) during peacetime signals that we aren't committed, and may invite aggression.
Of course we're not in the Cold War anymore, and a central European war is unlikely, but neither are the military personnel in Germany just defending Germany. The bases there give us capabilities to act in Africa and the Middle East as well as Europe. The 1990s interventions in the Balkans and Africa would have been much more difficult without the German bases, as would the 2000s interventions in the Middle East. Similarly, the bases in Korea and Japan allow us to act all over Asia, while preventing regional arms races and brinksmanship. It's about capabilities and being able to quickly react to unforeseen developments.
Maybe that rationale would not satisfy Sailer -- it doesn't satisfy Harvey Sapolsky -- but that is the rationale. It would be absurd if 60,000 American troops were only in Germany to defend that country. But that's not why they're there.