 Historians Parshall and Tully believe that by combining the surviving aircraft and pilots from Shōkaku and Zuikaku , it is likely that Zuikaku could have been equipped with almost a full composite air group . They also note that doing so would have violated Japanese carrier doctrine , which stressed that carriers and their pilots must train as a single unit ( in contrast , American training was only conducted at the squadron level ) . In any case , the Japanese apparently made no serious attempt to get Zuikaku ready for the forthcoming battle . 
