Getting 66,000 U.S. troops out of Afghanistan over the next 22 months is the easy part. Colonel Andrew Rohling of the 173rd Airborne Brigade knows all about the hard part. In July 2012, he and his paratroopers arrived at Forward Operating Base Shank, the third largest U.S. military installation in Afghanistan, to find a sea of 20-ft.-long (6 m) shipping containers. They were stacked behind the gym, arrayed in dirt yards and lined up by the hundreds along roadways. Rohling ordered a census and came up with about 8,000--a figure that outnumbered the troops on base by nearly 2,000.
Inside the...