The 007 number assigned to James Bond may have been influenced by any number of sources. In the films and novels, the 00 prefix indicates Bond's discretionary 'licence to kill', in executing his duties. Bond's number—007—was assigned by Fleming in reference to one of British naval intelligence's key achievements of World War I: the breaking of the German diplomatic code.[47] One of the German documents cracked and read by the British was the Zimmermann Telegram, which was coded 0075,[48] and which was one of the factors that led to the US entering the war. Subsequently if material was graded 00 it meant it was highly classified and, as journalist Ben Macintyre has pointed out, "to anyone versed in intelligence history, 007 signified the highest achievement of British military intelligence.