 At 02 : 15 on the night of 5 / 6 June , Commander John Murphy 's Tambor , lying 90 nautical miles ( 170 km ; 100 mi ) west of Midway , made the second of the submarine force 's two major contributions to the battle 's outcome , although its impact was heavily blunted by Murphy himself . Sighting several ships , neither Murphy nor his executive officer , Ray Spruance , Jr . , could identify them . Uncertain of whether they were friendly or not and unwilling to approach any closer to verify their heading or type , Murphy decided to send a vague report of " four large ships " to Admiral Robert English , Commander , Submarine Force , Pacific Fleet ( COMSUBPAC ) . This report was passed on by English to Nimitz , who then sent it to Spruance . Spruance , a former submarine commander , was " understandably furious " at the vagueness of Murphy 's report , as it provided him with little more than suspicion and no concrete information on which to make his preparations . Unaware of the exact location of Yamamoto 's " Main Body " ( a persistent problem since the time PBYs had first sighted the Japanese ) , Spruance was forced to assume the " four large ships " reported by Tambor represented the main invasion force and so he moved to block it , while staying 100 nautical miles ( 190 km ; 120 mi ) northeast of Midway . 
