GERMANY'S FIRST CRYPTANALYSIS ON THE WESTERN FRONT: DECRYPTING BRITISH AND FRENCH NAVAL CIPHERS IN WORLD WAR I

Beginning in December 1914, staff members of the Bavarian Sixth Army wireless telegraphy command broke into the low-grade cipher system of the Royal Navy and worked their way up to high-grade codes. They also solved two French high-grade codes. In December 1915 a provisional army office was created for the interception and decryption of British naval wireless-telegraphy (w/t) communications. In January 1917, coincidental with the beginning of unrestricted submarine warfare, this unit became a regular army unit.