Recently I mentioned the Ace of Spades playing card that the CIA allegedly left on the body of assassinated U.N. Secretary General in 1961.

Here’s some more reference from WWII on the American military intelligence habit of playing with cards.

During World War II, Bicycle teamed up with British and American intelligence agencies to create a deck of cards that peeled apart when wet. The cards then revealed secret escape maps so downed pilots and captured soldiers could navigate their way back to Allied lines.

These cards worked so well that dozens of Americans were reported to have escaped using them.