In 1942, Lawrence Pritchard Waterhouse, a young U.S. Navy code breaker and mathematical genius is assigned to the newly formed joint British and American Detachment 2701. This is quickly changed to 2702 after Waterhouse points out the original designation is the product of two primes, 37 and 73. This ultra-secret unit's role is to hide the fact that Allied Intelligence has cracked the German Enigma code. The detachment stages events, often behind enemy lines, that provide alternative explanations for the Allied intelligence successes. Marine sergeant Bobby Shaftoe, a veteran of China and Guadalcanal, serves in unit 2702, carrying out Waterhouse's plans.

[Source: Wikipedia http://en.wikipedia.org/wiki/Cryptonomicon ]