Escape maps were printed on Bicycle playing cards distributed to Allied prisoners of war during World War II. The deck of cards was specifically created to help Allied prisoners of war escape from German POW camps. This deck of cards became known as the “map deck.” It was made by hiding maps of top-secret escape routes between the two paper layers that make up all modern playing cards. These decks, when soaked in water, could be peeled apart to reveal hidden maps that allowed escaping prisoners to find their way to safety.
They were given to prisoners as Christmas presents. The German captors, unaware of the maps, willingly distributed the cards to the prisoners.
Only two decks are known to survive from this period, and one is owned by the International Spy Museum in Washington, DC. Due to the nature of the war and the prosecution of war crimes thereafter, the map decks remained a closely guarded secret for many years after the war ended. The secrecy surrounding them was so high, that no one really knows how many were produced. The escape kits are credited with helping 316 escape attempts from Colditz Castle, which saw 32 men make it back home.