World War II: Pacific Theater

In addition to its role in cracking enemy codes, the Signal Security Agency (SSA) was also responsible for Army communications security. One of the simplest devices was the strip cipher. Even after the Army turned to cipher machines, the strip ciphers continued in use as a primary means of securing secret communications for low-echelon communications. Strip ciphers also remained important for use as a stand-by system in the event a cipher machine should, for any reason, become inoperative.

Notable among the SSA’s achievements was a highly sophisticated electromechanical cipher device, designated the SIGABA, which became the backbone of high-level US communications in all theaters of the war.

In the Pacific, as in Europe, each Army division had its own attached CIC detachment. On remote islands with few local civilians around the battle area, CIC teams helped out in a combat-intelligence capacity, securing enemy documents and materiel for exploitation. One such item is a very unusual type of aerial camera used by the Japanese. It has the appearance of a machine gun, and the film is “shot” by pulling the “trigger.”