 Japanese carrier doctrine preferred the launching of fully constituted strikes rather than piecemeal attacks . Without confirmation of whether the American force included carriers ( not received until 08 : 20 ) , Nagumo 's reaction was doctrinaire . In addition , the arrival of another land based American air strike at 07 : 53 gave weight to the need to attack the island again . In the end , Nagumo decided to wait for his first strike force to land , then launch the reserve , which would by then be properly armed with torpedoes . 
