 Admiral Isoroku Yamamoto, commander of the Combined Fleet, was concurrently planning an operation for June that he hoped would lure the U.S. Navy's carriers, none of which had been damaged in the Pearl Harbor attack, into a decisive showdown in the central Pacific near Midway Atoll.In the meantime Yamamoto detached some of his large warships, including two fleet carriers, a light carrier, a cruiser division, and two destroyer divisions, to support "Mo", and placed Inoue in charge of the naval portion of the operation.Unknown to the Japanese, the U.S. Navy, led by the Communication Security Section of the Office of Naval Communications, had for several years enjoyed some success with penetrating Japanese communication ciphers and codes.