10. The Japanese changed their naval codes just before the battle began
The story of American codebreakers gaining full knowledge of Japanese plans in the weeks before Midway is well known. Less known is the Japanese changed their codes just before the battle, leaving the Americans unable to listen to their plans during the last week of May, 1942. By then, most of the information needed to counter the Japanese blow was in Nimitz’s hands. The sudden change of the Japanese code raised some concerns in Washington, where officials at the Navy Department expressed the belief the massive operation was actually a planned attack on the American coast. Nimitz remained convinced the attack was intended for Midway Atoll.
When it became evident that Admiral Halsey was unavailable to command the American response (dermatitis), he recommended Rear Admiral Ray Spruance to command his task force. Nimitz concurred, though Spruance was not a carrier commander. Jack Fletcher, in Yorktown, was senior and thus would command the overall force. Fletcher and Spruance recommended the American fleet deploy to the northeast of Midway, a position designated Point Luck. By June 3, the three American carriers were on station, with their escorts, awaiting the appearance of the Japanese. American PBY search planes searched the daylight skies for the approaching enemy, and American submarines were positioned in its path.