device used by the German military command to encode strategic messages before and during World War II. The Enigma code was first broken by the Poles, under the leadership of mathematician Marian Rejewski, in the early 1930s. In 1939, with the growing likelihood of a German invasion, the Poles turned their information over to the British, who set up a secret code-breaking group, known as Ultra, under mathematician Alan M. Turing (Turing, Alan M.). Because the Germans shared their encryption device with the Japanese, Ultra also contributed to Allied victories in the Pacific. See also Cryptology: Developments during World Wars I and II (cryptology).