 Typical of Japanese naval planning during World War II , Yamamoto 's battle plan was exceedingly complex , requiring the careful and timely coordination of multiple battle groups over hundreds of miles of open sea . His design was predicated on optimistic intelligence suggesting that USS Enterprise and USS Hornet , forming Task Force 16 , were the only carriers available to the U.S. Pacific Fleet . During the Battle of the Coral Sea one month earlier , USS Lexington had been sunk and USS Yorktown damaged so severely that the Japanese believed she too had been lost . Yorktown deployed , after being hastily repaired at Pearl Harbor , and played a critical role in the discovery and eventual destruction of the Japanese fleet carriers at Midway . Much of Yamamoto 's planning , coinciding with the general feeling among the Japanese leadership at the time , was based on a gross misjudgement of American morale , which was believed to be debilitated from the string of Japanese victories in the preceding months . 
