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(Background to the Battle of Midway)

Background to the Battle of Midway

Following the outbreak of the Pacific War in December 1941, the Japanese armed forces conducted military operations against U.S., British Commonwealth, and Dutch possessions in the Pacific and Southeast Asia. The first phase of these operations, which was the seizure of Malaysia, Singapore, the Dutch East Indies, the Philippines, and various island groups in the central and western Pacific, was virtually complete by March 1942. The second phase, initiated by Japanese Imperial Headquarters on 23 January, was designed to isolate and neutralize Australia and India. In the Pacific, this plan envisioned the seizure of bases in Papua/New Guinea and the Solomon Islands, which would be used to support future operations against New Caledonia, Fiji, and Samoa. By early March, with the seizure of Lae and Salamaua, the entire north coast of Papua/New Guinea had fallen to Japanese forces who were planning for an amphibious invasion of Port Moresby.

By this time, two secure American naval intelligence centers were in operation in the Pacific: one in Melbourne, Australia, and another at Pearl Harbor ('Hypo'). A third, at Corregidor ('Cast'), was rapidly disintegrating under Japanese air and artillery attacks on the island. Its cryptanalysts and equipment were in the process of evacuation to Melbourne. These facilities intercepted Japanese radio communications and, through traffic analysis and codebreaking, uncovered the location of major fleet units and shore based air forces. More importantly, by translating messages and studying operational patterns, Melbourne and Hypo predicted future Japanese operations. The intelligence centers provided their analysis, through daily communications intelligence (COMINT) briefings and warning reports, to senior American commanders, including Commander in Chief, U.S. Fleet (Admiral Ernest J. King), and Commander in Chief, Pacific Fleet (Admiral Chester W. Nimitz).

In early March, the Japanese postponed their planned seizure of Port Moresby because of previous events. An American carrier raid on Japanese shipping at Lae and Salamaua on the 10th, along with a previously unsuccessful attempt to attack Rabaul on 20 February, had demonstrated to Commander in Chief, Fourth Fleet (Admiral Shigeyoshi Inouye), that Japanese were not assured of air superiority in the region. It was not until early May, when Admiral Inouye had three carriers for operations, that the invasion could begin. On 7-8 May, the first carrier battle of the war took place in the Coral Sea. Each side had a carrier damaged, while the American lost the carrier USS Lexington and the Japanese lost the light carrier Shoho. More important the Japanese broke off their invasion attempt. It was the first time the Japanese had been stopped in the Pacific. Significantly, American cryptanalysts had provided crucial order of battle and operational communications intelligence to the Allied commanders in the South Pacific.

In addition to this advance toward Port Moresby, evidence that Japan was intent on expanding east of the Marshall Islands appeared in COMINT in early 1942. Land-based air units and equipment began appearing in message traffic to and from the Marshall Islands and the Mandates. On 4 March, the designator 'AF' began appearing in partially decoded messages. Then, on 5 March, Japanese seaplanes, refueled from a submarine at French Frigate Shoals, Territory of Hawaii, conduct a small armed reconnaissance mission over Oahu. Finally, on 13 March, American cryptanalysts both broke the Japanese Navy's General-Purpose Code (JN 25) and identified 'AF' as Midway Island.

On 16 April, 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.

Two days later, Lieutenant Colonel James Doolittle and a small number of American airmen from the U.S. Army Air Corps took off from USS Hornet in land based 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 5 May, 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 7 May, 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 16 May. 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 9 May, 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 21 May. In response to this COMINT, American cryptanalysts supplied warning notices of Japanese offensives scheduled for late May.

On 19 May, 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 the 22nd, 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 26 May, since COMINT suggested the Japanese intended to approach from that direction, submarine USS Gudgeon (SS-211) sailed for a surface patrol northwest of Midway. Also on the 26th, aircraft ferry USS Kitty Hawk (AKV-1) arrived at Midway with reinforcements for Marine Air Group (MAG) 22, a light tank platoon earmarked for a mobile reserve, and the 3d Defense Battalion, equipped with 3-inch antiaircraft guns. On that same day, Task Force Sixteen (TF 16) under the command of Rear Admiral William F. Halsey, and centered around USS Hornet (CV- 8) and USS Enterprise (CV-6), returned to Pearl Harbor from the South Pacific to begin preparations for the upcoming battle. Although suffering from damage inflicted by Japanese bombs during the 7-8 May Battle of the Coral Sea, USS Yorktown (CV-5) returned the next day.

Also on the 26th, the Japanese Northern Force, which included two light carriers, sailed from Ominato toward the Aleutians. The next day, Japanese forces began getting underway for Midway. Chief among them was First Mobile Force, Carrier Strike Force (Vice Admiral Nagumo Chuichi), comprising the four large carriers Akagi, Kaga, Soryu, and Hiryu with a total of 229 carrier aircraft. On the 28th, the Japanese First Fleet, Main Body (Admiral Yamamoto in battleship Yamato) sortied from home waters. The Second Fleet, Escort Force (Rear Admiral Tanaka Raizo), including 15 transports, sailed from Saipan; Second Fleet, Occupation Support Force (Rear Admiral Kurita Takeo) sortied from Guam. These forces were supported by 17 patrol seaplanes.

TF 16 (Rear Admiral Raymond A. Spruance), formed around Enterprise and Hornet, departed Pearl Harbor on 28 May to take up a position northeast of Midway. Spruance replaced Halsey for this operation because Halsey was suffering from a painful attack of shingles. Two days later, Task Force Seventeen (TF 17) under the command of Rear Admiral Frank Jack Fletcher, formed around the quickly repaired Yorktown, and sailed from Pearl to join TF 16 northeast of Midway. When TF 17 and TF 16 joined about 350 miles northeast of Midway on 2 June, Rear Admiral Fletcher became officer in tactical command. The three American carriers, augmented by cruiser-launched floatplanes, provided 234 aircraft afloat. These were supported by 110 fighters, bombers, and patrol planes at Midway. As part of pre-battle disposition, 25 fleet submarines under the command of Rear Admiral Robert H. English were deployed around Midway.

Meanwhile, on 29 May, seaplane tender (destroyer) USS Thornton (AVD-11) arrived at French Frigate Shoals to relieve light minelayer USS Preble (DM-20) on patrol station there. The presence of U.S. ships at French Frigate Shoals prevented the Japanese from refueling flying boats to reconnoiter Pearl Harbor. Although the Japanese could not visually confirm the departure of Task Forces 16 and 17 from Pearl Harbor, American preparations to defend Midway were on the verge of discovery anyway. Japanese COMINT stations not only learned of carrier movements in and out of Pearl Harbor, simply by listening to increased air-ground radio chatter, but traffic analysis of 'Urgent' American radio messages coming out of Pearl Harbor suggested at least one Task Force was at sea. Incredibly, these discoveries by Japanese COMINT were withheld from the Midway Strike Force because of Yamamoto's strict radio silence restrictions.

On 3 June, in the preliminary moves of the Battle of Midway, American land-based aircraft from Midway located and attacked Japanese transports about 600 miles west of Midway Island. U.S. Army Air Force Boeing B-17 ('Flying Fortress') bombers inflicted no damage, however, and four Consolidated PBY ('Catalinas') from VP-24 were sent out for a night attack on the approaching transports. As part of the overall Japanese plan, the Second Strike Force (Rear Admiral Kakuta Kikuji) bombed Dutch Harbor with planes from light carriers Ryujo and Junyo. In an event whose importance became clear only later, one Mitsubishi A6M ('Zeke') carrier fighter was disabled by antiaircraft fire and made an emergency landing on Akutan Island. The pilot, fooled by the flat ground, flipped the plane over upon landing in a bog and was killed. American intelligence analysts later studied the plane to discover its strengths and weaknesses.

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(Background to the Battle of Midway)