The Japanese probably didn't wargame the possibility that cryptography by the Allies revealed their plans. See [1], where General George Marshall is quoted as

The Japanese probably didn't wargame the possibility that cryptography by the Allies revealed their plans. See [1], where General George Marshall is quoted as saying: "as a result of Cryptanalysis we were able to concentrate our limited forces to meet their naval advance on Midway when we otherwise would have been 3,000 miles out of place." [1] [1] http://www.navy.mil/midway/how.html http://www.navy.mil/midway/how.html