 In reality , the ships sighted by Tambor were the detachment of four cruisers and two destroyers Yamamoto had sent to bombard Midway . At 02 : 55 these ships received Yamamoto 's order to retire and changed course to comply . At about the same time as this change of course , Tambor was sighted and during maneuvers designed to avoid a submarine attack , Mogami and Mikuma collided , inflicting serious damage on Mogami 's bow . The less severely damaged Mikuma slowed to 12 knots ( 22 km / h ; 14 mph ) to keep pace . Only at 04 : 12 did the sky brighten enough for Murphy to be certain the ships were Japanese , by which time staying surfaced was hazardous and he dived to approach for an attack . The attack was unsuccessful and at around 06 : 00 he finally reported two westbound Mogami @-@ class cruisers , before diving again and playing no further role in the battle . Limping along on a straight course at 12 knots — roughly one @-@ third their top speed and only 1 knot faster than Tambor while submerged — Mogami and Mikuma had been almost perfect targets for a submarine attack . As soon as Tambor returned to port , Spruance had Murphy relieved of duty and reassigned to a shore station , citing his confusing contact report , poor torpedo shooting during his attack run and general lack of aggression , especially as compared to Nautilus , the oldest of the 12 boats at Midway and the only one which had successfully placed a torpedo on target ( albeit a dud ) . This was in the context as referenced above , of mistaken criticism of submariner performance for severe ineffectiveness of navy torpedoes , already reported as technical by submariners , but unaddressed until 1943 . 
