A routine internet search for military study material once returned much more than definitions and test questions. Public flashcard sets connected to European air bases contained shelter numbers, alarm procedures, camera locations and coded words used by guards responsible for protecting nuclear weapons. Military personnel had placed sensitive details about U.S. nuclear weapons in Europe into publicly searchable study sets. The shelters can be seen in publicly available satellite imagery of Volkel Air Base, although the imagery does not show what each structure contains. A separate set associated with Aviano Air Base contained more than 80 cards.