Ultra was the designation adopted by
British military intelligence in June 1941 for wartime
signals intelligence obtained by breaking high-level
encrypted enemy
radio and
teleprinter communications at the Government Code and Cypher School (GC&CS) at
Bletchley Park.
Ultra eventually became the standard designation among the western
Allies for all such intelligence. The name arose because the intelligence thus obtained was considered more important than that designated by the highest British
security classification then used (
Most Secret) and so was regarded as being
Ultra secret. Several other
cryptonyms had been used for such intelligence. British intelligence first designated it
Boniface—presumably to imply that it was the result of
human intelligence. The U.S. used the codename
Magic for its decrypts from Japanese sources.