8. The Japanese expected to fight the impulsive William Halsey
Imperial Japanese Navy planners believed the American commander at Midway was William Halsey. Halsey was known for his aggressive nature, and the Japanese believed they could turn his natural combativeness against him. Japanese plans were to take Midway and then prepare for an American counterattack, led by Halsey in Enterprise, supported by USS Hornet. They believed both Yorktown and Lexington had been sunk at Coral Sea (Lexington had) and the Americans would be facing four carriers with only two of their own. Their plan was predicated on the Americans being taken by surprise by the attack on Midway, their fleet in port at Pearl Harbor.
In March 1942, Japanese reconnaissance aircraft flew over Pearl Harbor. American intelligence learned the Japanese had flown to French Frigate Shoals, refueled from a submarine, and then flown on to Pearl Harbor. Admiral Nimitz was concerned that a similar operation would allow the Japanese to learn of his preparations to defend Midway. Nimitz ordered the area mined and increased American warship patrols. Japanese aircraft did attempt to repeat the reconnaissance, but the refueling submarine was unable to approach due to the mines and two American warships present at the rendezvous. The reconnaissance flight was canceled.