 To do battle with an enemy expected to muster four or five carriers , Admiral Chester W. Nimitz , Commander in Chief , Pacific Ocean Areas , needed every available U.S. flight deck . He already had Vice Admiral William Halsey 's two @-@ carrier ( Enterprise and Hornet ) task force at hand , though Halsey was stricken with severe dermatitis and had to be replaced by Rear Admiral Raymond A. Spruance , Halsey 's escort commander . Nimitz also hurriedly recalled Rear Admiral Frank Jack Fletcher 's task force , including the carrier Yorktown , from the South West Pacific Area . 
