 What Yamamoto did not know was that the U.S. had broken the main Japanese naval code ( dubbed JN @-@ 25 by the Americans ) . His emphasis on dispersal also meant none of his formations were in a position to support each other . For instance , despite the fact Nagumo 's carriers were expected to carry out strikes against Midway and bear the brunt of American counterattacks , the only warships in his fleet larger than the screening force of twelve destroyers were two battleships , two heavy cruisers , and one light cruiser . By contrast , Yamamoto and Kondo had between them two light carriers , five battleships , four heavy cruisers , and two light cruisers , none of which saw action at Midway . The battleships and the small carriers of the trailing force were unable to keep pace with the carriers of the Kido Butai and so could not have sailed in company with them , while the distance between Yamamoto and Kondo 's forces and Nagumo 's carriers had grave implications during the battle : the invaluable reconnaissance capability of the scout planes carried by the cruisers and carriers , as well as the additional antiaircraft capability of the cruisers in the trailing force , was denied to Nagumo . 
