Ultra, short for ultra-secret, was an Allied intelligence system that, in tapping the very highest-level communications among the German armed forces, as well as (after 1941) those of the Japanese armed forces, contributed to the Allied victory in World War II.
The Ultra project was mainly involved with breaking the German's Enigma codes. These codes were generated by an electric device and considered to be unbreakable. The German Army, Navy, and diplomats all used Enigma machines, but the codes were different and each needed to be broken separately. There are several conflicting stories of how the Allies got hold of the physical Engima machines - see Enigma for these stories.
The group working on the breaking the code were an eclectic mix of crossword enthusiasts, mathematicians, and early computer scientists. The most noted participant was Alan Turing, one of the fathers of modern computing. The group worked at Bletchley Park in utter secrecy. They were quickly successful. By 1943 the incoming signals from the German war machine (more than 2,000 daily at the war's height) were of the highest level, even from Adolf Hitler himself. Such information enabled the Allies to build up an accurate picture of enemy plans and orders of battle, forming the basis of war plans both strategic and tactical.
The Allies were desperate to conceal from the Axis command that they had broken Enigma. This was to the extent that although they had intercepted and knew of the whereabouts of U-boats lying in wait in mid-Atlantic, often convoys were allowed to sail into their midst for fear of alerting the Axis to their knowledge.
Ultra was used to sink many of the supply ships travelling to North Africa, but every time it was used, it had to be arranged that alternate means of discovery were provided, so scout planes would often be sent on unnecessary and dangerous missions to ensure they were seen by the Germans.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ultra".