 Unknown to the Japanese, the US Navy had divined the Japanese plan by breaking its JN-25 code and had prepared an ambush using its three available carriers, positioned northeast of Midway.On 25 May 1942, "Hiryū" set out with the Combined Fleet's carrier striking force in the company of "Kaga", "Akagi", and "Sōryū", which constituted the First and Second Carrier Divisions, for the attack on Midway.Her aircraft complement consisted of 18 Zeros, 18 D3As, and 18 B5Ns.