Photo by Ron Bosley

As you may imagine, one of the most important parts of a POW's life was communicating with his fellow captives. Communication between prisoners was greatly enhanced when four POWs, Captain Carlyle Harris, Lieutenant Commander Robert Shumaker, Lieutenant Phillip Butler, and Lieutenant Robert Peel, developed this simple tap code while imprisoned in the same cell at Hoa Lo in June of 1965. When guards separated the four, the code spread as the original four men taught it to others. By August 1965, most of the prisoners had learned it and were passing messages by tapping on the walls to fellow prisoners.