Military intelligence played a significant role in the battle for Midway. The Americans had broken Japan's naval code and knew the IJN was coming and what it planned to do. Americans brought all three of their available carriers along with 233 carrier-launched aircraft to the battle. In addition, they had as many as 120 aircraft of various types at Midway's airfield, which was effectively an "unsinkable carrier." Sixty-seven of Midway's aircraft were bombers and fighters that, when added to American carrier-launched aircraft, resulted in a total of 300 such planes being available for the defense of the Midway.Parshall and Tully pp. 96, 434 This was more than the 248 aircraft that Yamamoto's battle plan would put in effective range of Midway during the attack. Kidō Butai's aircraft striking Midway were going to be out-numbered.
