What ever it was, I can almost guarantee that they were practicing "blacked-out" ops. You need to be proficient in that sort of stuff if you want to safely land of take off in hostile territory. No big secret, but most military aircraft flying in the sandbox will shut off all lighting right after takeoff and keep them out until at cruise altitude.
All of the above is only a guess
, since I would not have any first hand experience in that sort of thing.
Brandon