 As a result , the Americans entered the battle with a very good picture of where , when , and in what strength the Japanese would appear . Nimitz knew that the Japanese had negated their numerical advantage by dividing their ships into four separate task groups , all too widely separated to be able to support each other . This dispersal resulted in few fast ships being available to escort the Carrier Striking Force , reducing the number of anti @-@ aircraft guns protecting the carriers . Nimitz calculated that the aircraft on his three carriers , plus those on Midway Island , gave the U.S. rough parity with Yamamoto 's four carriers , mainly because American carrier air groups were larger than Japanese ones . The Japanese , by contrast , remained almost totally unaware of their opponent 's true strength and dispositions even after the battle began . 
