It was renamed the Department of Defense via the National Security Act of 1947.
This was also when the US Air Force was established, and civilian secretaries were placed over the military brances. There were other changes, of course, but those seemed significant enogh to remember.
The Department of Defense was established by the National Security Act of 1947
24 posted on 6/6/02 8:32 PM Eastern by APBaer
I stand corrected. I believe (I hope I don't get it wrong again) it was the Department of War that got renamed to the Army.