““Unbeknownst to the Japanese, the main disadvantage Japan would have at Midway was the fact the U.S. could read their radio traffic. With the success of their codebreakers, Americans were able to understand Japan’s communications in the Pacific in the days leading up to the battle, and even when the routine issue of new Japanese code books meant that the Americans were once again in the dark, analysts working for the Navy in Hawaii were reasonably confident that as the Japanese units left port, Midway was their target and June 4 would be the date of their arrival.””
