It was an exercise in the unthinkable: a 10-kiloton nuclear bomb has decimated a major city in the Midwestern U.S. What will the military do?

More than 9,000 troops and civilians from across the country descended on Indiana and northern Kentucky to find out, during the 19-day Vibrant Response exercise. The exercise, led by U.S. Army North out of Fort Sam Houston, Texas, wrapped up Aug. 13 and included local, state and federal agencies, and involved 300,000 casualties and military units from more than 40 locations across the U.S.

The intent is to allow the military to practice interacting with civilian agencies and test the military's ability to deploy, employ and sustain specialized military response forces in the aftermath of a catastrophic chemical, biological, radiological and nuclear event.

Photos from the exercise can be viewed here.