The work that the code breakers at Bletchley park did prevented a lot of Ally deaths. When the Germans instituted using the 4-wheel enigma it was impossible to tell what the U-boats were doing out in the Atlantic Ocean. Because of this, supply boats going to the U.K. were being sunk at a high rate, unable to avoid the U-boats, eventually the Brits could have been forced out of the battle (no war supplies == no war). Near the end of 1942 however, some documented daily settings on the new 4-wheel enigma were pulled off of a sunken U-boat in the Mediterranean allowing german naval deciphers to be broken. Through the man-power, knowledge, and tools available at Bletchley, they could decipher and relay german naval messages (at least in the Atlantic) to high command often within hours of obtaining them. After this, supply ships in the Atlantic were nearly invisible to German U-boats. The monthly settings booklets still had to be retrieved to continue this, but through missions and sometimes luck most of them were captured

That's the WWII side of the story (or at least a very small part of it).

The importance to /. is probably that this war was the first time machines were used to cipher messages, and thus machines had to do the deciphering. To break the regular ground enigma's daily settings scientists at Bletchley designed and manufactured the Colossus(es). If you ever see this thing run, especially the interior mechanisms, you'll know this was a great unknown leap towards multi-purpose computing machinery. Unfortunately because of U.K. laws, the work and knowledge of those at Bletchley couldn't be released until sometime in the 80's (I think)