During the third week of May 1942, U.S. naval intelligence units confirmed that the Japanese would—by early June—invade Midway Island. Capturing and occupying Midway was the brainchild-plan of commander-in-chief of the Combined Fleet, Admiral Isoroku Yamamoto. With it he intended to significantly expand the Imperial Japanese Navy's outer defense perimeter across the central Pacific; and, he believed, this very powerful stroke against Midway would so severely threaten Hawaii and Pearl Harbor that the U.S. government would be induced to sue for peace. On the other hand, commander-in-chief of the U.S. Pacific Fleet, Admiral Chester Nimitz knew he must intercept the Japanese invasion fleet, and that he must give battle to the enemy aircraft carriers before they could project their overwhelming power against the naval air station at Midway.