Ever since WWII

In a recent post Andrew Sullivan asked "[W]hen did it become normal for one country to be stationing troops in the heart of another one?"

In brief: Ever since WWII. (Alas!)

We Americans have footed most of the defense spending bill for most of our regional strategic allies for over half a century now.

I'm still trying to find a map which adequately illustrates this point for Sullivan's readers' edification. This may take a little while, but for now, check this out:
http://www.nonviolenceworks.com/usmilitaryglobal.pdf