Changes

On April 16, after several months of discussion, Commander in Chief, Combined Fleet, Admiral [[Isoruku Yamamoto]], convinced the Imperial General Staff to agree to his Midway and Aleutians strategy for the summer. In Admiral Yamamoto's view, the capture of Midway Island would allow Japan to pursue its Asian policies behind an impregnable eastern shield of defenses in the Central Pacific. The centerpiece of this plan was a feint toward Alaska followed by an invasion of Midway. When the U.S. Pacific Fleet responded to the landings on Midway, Japanese carrier and battleship task forces, waiting unseen to the west of the Midway strike Force, would fall upon and destroy the unsuspecting Americans. If successful, the plan would effectively eliminate the U.S. Pacific Fleet for at least a year and provide a forward outpost from which ample warning of any future threat by the U.S. would come.

On April 16, after several months of discussion, Commander in Chief, Combined Fleet, Admiral [[Isoruku Yamamoto]], convinced the Imperial General Staff to agree to his Midway and Aleutians strategy for the summer. In Admiral Yamamoto's view, the capture of Midway Island would allow Japan to pursue its Asian policies behind an impregnable eastern shield of defenses in the Central Pacific. The centerpiece of this plan was a feint toward Alaska followed by an invasion of Midway. When the U.S. Pacific Fleet responded to the landings on Midway, Japanese carrier and battleship task forces, waiting unseen to the west of the Midway strike Force, would fall upon and destroy the unsuspecting Americans. If successful, the plan would effectively eliminate the U.S. Pacific Fleet for at least a year and provide a forward outpost from which ample warning of any future threat by the U.S. would come.

===The Doolittle Raid===

===The Doolittle Raid===

Two days later, Lieutenant Colonel James Doolittle and a small number of American airmen from the U.S. Army Air Corps took off from the carrier USS ''Hornet'' in land-based B-25 bombers to attack the Japanese home islands. As a result of this attack, which caused the Japanese to want to extend their first line of defense as far east as possible, the Japanese advanced the date of their planned attack on Midway. On May 5, Imperial General Headquarters issued "Navy Order No. 18" directing Admiral Yamamoto to carry out the occupation of Midway Island and key points in the western Aleutians in cooperation with the Army.

Two days later, Lieutenant Colonel James Doolittle and a small number of American airmen from the U.S. Army Air Corps took off from the carrier USS ''Hornet'' in land-based B-25 bombers to attack the Japanese home islands. As a result of this attack, which caused the Japanese to want to extend their first line of defense as far east as possible, the Japanese advanced the date of their planned attack on Midway. On May 5, Imperial General Headquarters issued "Navy Order No. 18" directing Admiral Yamamoto to carry out the occupation of Midway Island and key points in the western Aleutians in cooperation with the Army.

At the same time, Japanese Navy communication activity in the vicinity of Japan dramatically increased, reflecting naval exercises conducted in preparation for both the Midway and Aleutian operations. On May 7, Hypo provided a translation of the agenda for a Japanese aviation conference, called by Commander in Chief, 1st Air Fleet (Vice Admiral Nagumo), scheduled for May 16. The conference concerned tactics to be employed in obtaining air superiority over a target, assisting in amphibious landings, and bombing and strafing attacks to wipe out local resistance. On May 9 Melbourne intercepted and translated "1st Air Fleet Striking Force Order No. 6," which confirmed the creation of a new carrier strike force and that a major Fleet movement would begin on May 21. In response to this COMINT, American cryptanalysts supplied warning notices of Japanese offensives scheduled for late May.

At the same time, Japanese Navy communication activity in the vicinity of Japan dramatically increased, reflecting naval exercises conducted in preparation for both the Midway and Aleutian operations. On May 7, Hypo provided a translation of the agenda for a Japanese aviation conference, called by Commander in Chief, 1st Air Fleet (Vice Admiral Nagumo), scheduled for May 16. The conference concerned tactics to be employed in obtaining air superiority over a target, assisting in amphibious landings, and bombing and strafing attacks to wipe out local resistance. On May 9 Melbourne intercepted and translated "1st Air Fleet Striking Force Order No. 6," which confirmed the creation of a new carrier strike force and that a major Fleet movement would begin on May 21. In response to this COMINT, American cryptanalysts supplied warning notices of Japanese offensives scheduled for late May.

==American plans==

==American plans==

On May 19 the Officer in Charge of COMINT processing at Hypo (Commander Joseph J. Rochefort) and the intelligence officer for the Pacific Fleet (Lieutenant Commander Edwin T. Layton), identified Midway and Dutch Harbor, Aleutian Islands, as specific Japanese objectives. On May 22, following a radio deception operation, Melbourne completely confirmed that "AF" meant Midway. Hypo then discovered the date cipher used in Japanese message traffic. This meant analysts could determine exactly when the attack would take place. After examining previously intercepted messages, Hypo predicted an attack on Midway on 4 June. Admiral Nimitz used this estimate to plan American countermeasures.

On May 19 the Officer in Charge of COMINT processing at Hypo (Commander Joseph J. Rochefort) and the intelligence officer for the Pacific Fleet (Lieutenant Commander Edwin T. Layton), identified Midway and Dutch Harbor, Aleutian Islands, as specific Japanese objectives. On May 22, following a radio deception operation, Melbourne completely confirmed that "AF" meant Midway. Hypo then discovered the date cipher used in Japanese message traffic. This meant analysts could determine exactly when the attack would take place. After examining previously intercepted messages, Hypo predicted an attack on Midway on 4 June. Admiral Nimitz used this estimate to plan American countermeasures.