In mid-1942 the Imperial Japanese Navy laid plans to attack Alaska in conjunction with an attack on Midway Island in the central Pacific. The Japanese Northern Area Fleet's attacks on Dutch Harbor and Adak Island resulted in the Aleutian Islands Campaign. But because United States Naval intelligence had broken the Japanese naval cypher code, Admiral Nimitz, Commander-in-Chief Pacific Ocean Areas in Hawaii, learned of Japanese plans by 21 May 1942. As of 1 June 1942, United States military strength in Alaska stood at 45,000 men. On that day the XI Intercepter Command, activated earlier, in March, was redesignated the XI Fighter Command. However, Eleventh Air Force operational strength was small. It consisted of 10 B-17 Flying Fortress heavy bombers and 34 B-18 Bolo medium bombers at Elmendorf Airfield, and 95 P-40 Warhawk fighters divided between Fort Randall AAF at Cold Bay and Fort Glenn AAF on Umnak.