19. The Japanese could not accept that the Americans had broken their codes
For the Japanese, the plan which Yamamoto called Operation MI was a disaster. Many of their most combat-experienced pilots had been killed. The Japanese lost nearly 250 aircraft, four fleet carriers, and a heavy cruiser. 3,057 Japanese sailors and airmen were killed. Yet for the Japanese High Command, the most disturbing aspect of the failure was the potential loss of prestige. On June 15, 1942, Admiral Nagumo submitted his report of the operation (Admiral Yamaguchi died when Hiryu sank). In his report, Nagumo wrote, “The enemy is not aware of our plans (we were not discovered until early in the morning of the 5th at the earliest)”.
The disparity of the date was because Japan sits on the other side of the International Date Line. What was surprising about the report was there was no speculation about why the American fleet was there. The Japanese refused to believe that the Americans had broken their naval codes. Even after Admiral Yamamoto was ambushed and killed while on a tour of the front in 1943 the Japanese refused to consider the possibility that their communications were compromised. The Americans continued to listen to Japanese coded information throughout the war, an advantage conferred by their enemy’s contempt of westerners and belief in their own superiority.