Ultra in a Nutshell

Enigma device

Ultra was a codename used by the Allied powers to refer to the signals intelligence gained via the clandestine interception of encrypted German communications via their so-called Enigma encryption devices. Intercepted German transmissions were decoded by Allied intelligence experts then disseminated to senior commanders.

The breaking of the Enigma code was “largely the work of Polish intelligence services,” who shared their knowledge with British and French intelligence in 1939 as it became clear that there would soon be war.[1] During the war, Allied Ultra operations were conducted in secrecy at Bletchley Park in England. By April, 1940 “some messages were being read within 24 hours of dispatch …. By the time of the D-Day landings, the Naval Enigma was being broken almost instantly.”[2]

The Germans never suspected that a vulnerability existed within their communications procedures and that the Allies were so effectually exploiting it. ‘Ultra intercepts,’ as they were called, were like a “secret weapon” for the Allies. Unfortunately, the intelligence gained from those intercepts was never a guarantee that the best military decisions would be made. In the run up to Operations MARKET-GARDEN, for example, it was learned through Ultra that “some of Germany's best panzer divisions would be refitting in the town selected as the goal of the British 1st Airborne Division and the operation's final objective on the Rhine [River]—Arnhem.”[3] Though Field Marshal Montgomery’s headquarters was aware of the intelligence, they altered nothing in their plans, and the rest, as is often said, is history.


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[1] John Barrat, “Enigma and Ultra: The Cypher War,” Military History Online, http://www.militaryhistoryonline.com
/wwii/atlantic/enigma.aspx (accessed 25 July 2012).

[2] Ibid.

[3] Williamson Murray, “World War II: Ultra—The Misunderstood Allied Secret Weapon,” Historynet.com, http://
www.historynet.com/world-war-ii-ultra-the-misunderstood-allied-secret-weapon.htm (accessed 25 July 2012).