The very complex Japanese Navy plan for the Midway and Aleutian operations required careful cooperation by five separate groups of warships, and precise coordination of ship movements over a very large area of the Pacific Ocean stretching from Alaska to the central Pacific. All of this had to be achieved while maintaining strict radio silence. A huge fleet of about 200 Japanese warships, transports, and oilers was assembled for the Midway and Aleutian offensives. It included eleven battleships, five large fleet aircraft carriers, three light aircraft carriers, twenty-three cruisers, sixty-seven destroyers, and twenty-two submarines. The Japanese fleet was divided into five main commands: Main Force (Admiral Isoroku Yamamoto, aboard the giant battleship Yamato ), First Carrier Striking Force, or Kido Butai, (Vice Admiral Chuichi Nagumo, who led the carrier attack on Pearl Harbor), Midway Invasion Force (Vice Admiral Nobutake Kondo), Northern Aleutians Force, and the Advance Submarine Force.

Rear Admiral Frank J. Fletcher was the commander of the American carrier task forces at the vital battles of Coral Sea and Midway. As senior tactical commander, he played an important part in securing Allied victories in both battles. In an extraordinary act of patriotism and generosity, he passed overall command of the American carrier task forces at Midway to Rear Admiral Spruance after his own flagship USS Yorktown had been disabled by Japanese dive bombers and after the Americans had already destroyed three of Japan's most powerful carriers.

The Japanese offensive against America's Aleutian Islands off the western coast of Alaska would take place on 3 June 1942, and was intended by Navy General Staff to provide a northern anchor for Japan's eastern defensive perimeter in the Pacific. Admiral Yamamoto hoped that the Aleutian operation would distract the attention of the United States from Midway Atoll which was the focus of his main attack.

Planning the attack on Midway Atoll

The Japanese had planned that their Midway offensive would take place in three separate phases. In the first phase, the large fleet aircraft carriers of Vice Admiral Chuichi Nagumo's powerful First Carrier Striking Force (Kido Butai ) would approach Midway Atoll from the north-west on 4 June 1942. In the pre-dawn darkness, Nagumo would launch aircraft from his four carriers to attack the American air and land defences on Sand and Eastern Islands. When the American defences on Midway had been neutralised by Nagumo's carrier-launched air attacks, the second phase would begin. Warships and transports of the Midway Invasion Force commanded by Vice Admiral Nobutake Kondo would approach Midway from the south-west and land troops to crush all resistance, occupy the islands, and prepare the airfield to receive Japanese combat aircraft. Having neutralised Midway Atoll and prepared it for Japanese occupation, the third phase required Vice Admiral Nagumo to wait in ambush with his carrier force for the anticipated arrival of carriers of the United States Pacific Fleet on or soon after 6 June. When the American Pacific Fleet arrived from Pearl Harbor to defend Midway, Admiral Nagumo would destroy it. Admiral Yamamoto would hold the powerful battleships of his Main Force in reserve west of Midway to provide any support that Vice Admiral Nagumo might require to destroy the American fleet.

The man responsible for planning the Japanese amphibious landing on Midway Atoll was Commander Yasumi Toyama. Toyama laboured under a number of serious disadvantages. The only maps of Midway Atoll in his possession were old and likely to be unreliable. Toyama had no aerial photographs of the atoll because the pilots of Marine Fighter Squadron VMF-221 had intercepted and shot down a Japanese four-engined Kawanishi 97 "Mavis" patrol flying boat that had been approaching Midway on 10 March 1942. This Japanese flying boat had come from Wake Island and had been assigned to carry out a photographic reconnaissance of Midway to provide intelligence for the Japanese amphibious assault on Midway in June.

Toyama had no intelligence concerning the defences of Midway and the number of defenders. The Navy planners expected to face about 750 US Marines, and that would have been the pre-war strength of the Midway Detachment, Fleet Marine Force. The Army estimate was more realistic; they expected that the Marine strength would be closer to 2,000. It was anticipated that the Marines might have between 50-60 planes on the atoll.

Toyama planned a simultaneous attack on Sand and Eastern Islands from the southern side of the atoll where the two islands were close to the reef. The Japanese landing force would number about 5,000, and would be spearheaded by two elite assault units - Captain Minoru Ota's 2nd Combined Special Naval Landing Force numbering about one thousand five hundred marines, and the Army's Ichiki Detachment which numbered about two thousand men and was commanded by Colonel Kiyonao Ichiki.

Captain Ota's marines would land on Sand Island, and Colonel Ichiki's troops would land on Eastern Island. Both landings would require flat-bottomed landing boats, and the Japanese Navy had none. Toyama would have to swallow his pride and borrow landing boats from the Japanese Army.

Planning the destruction of the United States Pacific Fleet

The Japanese Navy planners believed that warships of the United States Pacific Fleet would be sent from Hawaii to defend Midway as soon as Admiral Nimitz became aware that America's vital military outpost was under Japanese attack. The warships of Admiral Nagumo's First Carrier Striking Force (Kido Butai ) would then destroy the American aircraft carriers and complete the work begun by him at Pearl Harbor on 7 December 1941.

In planning the Midway offensive, the Japanese military leadership was influenced by a number of dangerous assumptions. Buoyed by easy initial victories produced by surprise attacks on British and American outposts in the Pacific region that were unprepared for war with Japan, many Japanese military leaders believed that Japan's samurai warrior tradition made their nation invincible in war. They believed that Americans lacked courage, fighting skills and discipline, and having inflicted heavy damage on the United States Pacific Fleet during their surprise attack on Pearl Harbor, they assumed that the United States Navy would thereafter adopt a largely defensive posture in response to further Japanese military aggression.

The Japanese Navy planners believed that their Midway offensive would take the United States completely by surprise, and that Japan would retain the initiative throughout the complex offensive. The assumption that the Japanese attack would take the Americans by surprise led to Japan's First Carrier Striking Force (Kido Butai ) being assigned two major missions at Midway. The first was to neutralise the defences of the two Midway islands by aerial bombardment. When the first mission had been completed, the second, and more vital mission, was to lie in wait off Midway for the expected arrival of aircraft carriers of the United States Pacific Fleet on or soon after 6 June, and destroy the American fleet. The Japanese appear to have failed to appreciate that both missions could be seriously compromised if unforeseen circumstances forced them to be undertaken simultaneously.

The arrogant belief in Japan's invincibility, and the underrating of American military capabilities and response, would be reflected in the planning and execution of the Midway offensive with serious consequences for Japan.

American code-breakers learn of Japan's plan to attack Midway

As the Japanese invasion forces converged on the Aleutian and Midway islands, Japan's admirals were supremely confident that the Americans would remain unaware that Midway was their primary target until the first bombs began falling on the Midway islands. The confidence of the Japanese admirals was misplaced. American naval intelligence and Allied code-breakers had achieved considerable success in deciphering the Japanese Navy's signal code JN 25.

The commander of the US Navy's Combat Intelligence Unit (Station Hypo) at Hawaii, Commander Joseph J. Rochefort, had analysed Japanese signal intercepts and correctly predicted the Japanese attempt to capture Port Moresby that was frustrated in the Battle of the Coral Sea. In the second half of April 1942, Commander Rochefort was becoming convinced from aspects of intercepted signal traffic between major units of Japan's Combined Fleet that the Japanese were preparing to launch another major naval offensive in the Pacific. Rochefort also noticed that the code reference "AF" was increasingly appearing in Japanese Navy signal traffic as a destination. Rochefort and his team of code-breakers began to concentrate their efforts on identifying the location of AF. It was recalled that two Japanese flying boats had made an abortive attack on Pearl Harbor in March 1942. The flying boats had refuelled from a submarine at French Frigate Shoals, a tiny atoll lying between Pearl Harbor and Japanese-occupied Wake Island and south-east of Midway. An intercepted signal from the flying boats mentioned that they had passed near AF. The only significant land feature in that area was Midway Atoll, and Rochefort was now convinced that AF referred to Midway. He was also convinced that Midway was the target of the impending Japanese naval offensive.

The Commander in Chief of the United States Pacific Fleet (CINCPAC), Admiral Chester W. Nimitz, was persuaded by Rochefort that Midway was the probable target of the next Japanese naval offensive. On 2 May 1942, Admiral Nimitz flew from Pearl Harbor to Midway and spent several hours examining its defences. Nimitz did not mention any specific threat to Midway but he asked the senior Navy and Marine officers, Commander Cyril T. Simard and Lieutenant Colonel Harold Shannon, what they would need to defend Midway against a major Japanese attack. When Simard and Shannon told Admiral Nimitz what they needed, he promised to provide it.

Some of Rochefort's superiors in Washington doubted the correctness of his conclusion that AF referred to Midway. They believed that Hawaii, Alaska, or even the American West Coast were more likely targets of a major Japanese naval offensive. The Commander in Chief US Fleet (COMINCH), Admiral Ernest J. King, shared their doubts about AF being a reference to Midway. Admiral King felt that AF was more likely to be a reference to Hawaii. Fortunately for Commander Rochefort, he had won the full support of Admiral Nimitz for his conclusion that AF referred to Midway. Despite that support, Washington remained sceptical, and Rochefort accepted that he could not offer concrete proof of the meaning of AF. Around 10 May 1942, Rochefort came up with a plan that he felt could identify AF beyond all reasonable doubt. Admiral Nimitz approved what was to become one of the most famous ruses of the Pacific War. Midway was instructed by undersea cable to transmit by radio in plain English a false message to the effect that the atoll's machinery for producing fresh water had broken down and that Midway was short of fresh water. Midway sent the fake message. It was picked up by a Japanese signal unit on a Pacific island, and the message was passed on by radio to Tokyo. The Japanese signal reported "AF is short of water". Rochefort now had his proof beyond reasonable doubt.

Nimitz began assembling whatever ships he could muster to meet the threat from Japan. Yorktown had been badly damaged in the Battle of the Coral Sea and was undergoing repairs to hull damage at Tonga. The carriers Enterprise and Hornet had arrived too late to take part in that battle and were patrolling off the Solomons. This turned out to be fortunate. The two carriers were sighted by a Japanese patrol plane, and this sighting caused the Japanese to believe that they might be out of the way when the Japanese struck at Midway. Nimitz ordered the three carriers to return to Hawaii as quickly as possible.

Despite the overwhelming size and power of the Japanese Midway forces opposing them, and the significant advantages possessed by the Japanese Imperial Navy in number of aircraft carriers, training of pilots, battle experience, and superior equipment, advance knowledge of Japan's military plans gave the Americans a vital advantage. They would know the dispositions of the approaching Japanese invasion forces, the direction each force would take as it approached Midway, and the approximate time of arrival of each force at Midway. With this vital knowledge, the United States Navy could prepare its own ambush for Admiral Nagumo's First Carrier Striking Force even as it was still approaching Midway from the north-west.

The Americans prepare to ambush Japan's First Carrier Striking Force off Midway

Against the awesome Japanese Midway invasion armada, the Americans would only be able to field three aircraft carriers, eight cruisers, fourteen destroyers, and nineteen submarines. These warships were effectively all that remained to the United States Pacific Fleet for the looming confrontation at Midway after Japan's devastating sneak attack on Pearl Harbor on 7 December 1941.

Admiral Nimitz decided to concentrate his three aircraft carriers in two task forces on the northern approaches to Midway Atoll. He knew that his warships would be outnumbered by the Japanese, and that many of his Navy aircrews had little or no actual combat experience. To reduce the heavy odds against his ships and men, the Admiral intended to ambush Vice Admiral Nagumo's First Carrier Striking Force while its aircraft were engaged in bombing Midway if surprise could be achieved. While awaiting the arrival of the Japanese, Nimitz strengthened the ground and air defences of Midway. Eastern Island was crammed with US Navy, Marine Corps, and Army Air Corps aircraft. Many of the pilots and aircrew members on Midway lacked experience with the aircraft they were flying, and few had combat experience. Many of the planes on Midway were discards from US Navy carriers whose performance fell far below that of aircraft Japanese fleet carriers.

The American carrier task forces were placed under the overall command of Rear Admiral Frank J. Fletcher, whose aircraft carrier USS Yorktown had only recently returned to Pearl Harbor carrying significant battle damage from Coral Sea. The integrity of the Yorktown's hull would need to be assured by repairs to external plating and, in particular, replacement of water-tight doors damaged when a 250-pound bomb penetrated several decks before exploding.

Task Force 16, comprising the carriers USS Enterprise and USS Hornet, six cruisers, and nine destroyers, was placed under the command of Rear Admiral Raymond Spruance. Admiral Spruance left Pearl Harbor and set course for Midway on 28 May 1942. Task Force 17 was delayed at Pearl Harbor for a further two days because Yorktown was still undergoing repairs to her battle damage. Task Force 17, comprising Yorktown, two cruisers and five destroyers, departed Pearl Harbor for Midway on 30 May with Admiral Fletcher aboard. On 2 June, the two American carrier task forces were about 200 miles (320 km) north of the Midway Islands, and Admiral Fletcher waited for news of the location of Vice Admiral Nagumo's carrier force.

Rear Admiral Raymond Spruance commanded carriers Enterprise and Hornet at Midway.

The first Stage of the Japanese Offensive begins off Alaska, 3 June 1942

In furtherance of the Japanese Midway plan, carrier-launched aircraft of the Northern Aleutians Force struck at the Alaskan town of Dutch Harbor on 3 June 1942. Being aware that the real purpose of the Japanese offensive was the capture of Midway Atoll, the United States refused to allow its attention to be diverted to the northern Pacific.

The refusal of the Americans to be distracted by the diversionary offensive against Alaskan islands was the first of a series of breakdowns in the overly complex Japanese Midway plan. The Japanese could not decode American signal traffic, and they were forced to make educated guesses about the likely direction and nature of the American response to their attack on the Midway islands. They believed that a response would be mounted by the United States Pacific Fleet from Hawaii, but only after its commander learned of the Japanese attack on Midway planned to begin on 4 June. This scenario would give Japan's invasion forces at least two days, or until 6 June, to occupy the two Midway islands before Admiral Nagumo's carrier force would be likely to engage American warships. While awaiting the expected arrival of American warships at Midway, the Japanese would be able to employ this time usefully by crushing all resistance, occupying the Midway islands, and preparing the airfield for use by Japanese combat aircraft.

The underrating of American military capabilities and response would have unpleasant consequences for Japan. The Japanese Midway plan provided for deployment of three submarine cordons between Midway and Hawaii to detect and give warning of the approach of American warships. However, by the time the Japanese submarine cordon was in place on 3 June, the two American carrier task forces had already reached waters north of Midway, and the Japanese invasion forces converging on Midway were unaware of the reception that Admiral Fletcher was preparing for them.

On the Midway islands, American marines were hard at work strengthening fortifications, and Navy PBY Catalina flying boats and Army Air Force B-17s were conducting reconnaissance sweeps of the sea to the west and north of the islands in an attempt to locate the approaching Japanese. On 3 June, one of the Catalinas located the troop transports and covering warships of Vice Admiral Kondo's Midway Invasion Force approaching the islands from the south-west. Army Air Force B-17 bombers from Midway attacked the troop transports and the covering warships without inflicting significant damage. While this preliminary skirmish was taking place, Rear Admiral Fletcher was placing his three carriers in position to launch a flank attack on Vice Admiral Nagumo's carriers while they were occupied in attacking the American base on Midway.

Vice Admiral Nagumo's First Carrier Striking Force approaches Midway

During the day and night of 3 June, thick fog had shrouded Admiral Nagumo's First Carrier Striking Force as it approached the Midway Islands from the north-west. The Nagumo force comprised four of Japan's most powerful aircraft carriers- Akagi, Kaga, Soryu and Hiryu - and was escorted by two fast battleships, two heavy cruisers (each capable of launching five seaplane scouts), one light cruiser, and twelve destroyers. This was not the same carrier striking force that had launched the devastating surprise attack on the United States Pacific Fleet at Pearl Harbor on 7 December 1941. The commander was the same man, but two powerful fleet carriers were missing on this occasion. The carrier Shokaku had been severely damaged at the Battle of the Coral Sea less than a month earlier, and the carrier Zuikaku had lost too many aircraft and aircrews in that battle to be capable of involvement in the Japanese offensive at Midway.

Vice Admiral Chuichi Nagumo commanded Japan's Carrier Striking Force at Midway.

On the bridge of Akagi, Admiral Nagumo was pleased to have thick fog screening his carrier force as it neared Midway, but the bad weather conditions had also prevented air reconnaissance sweeps by his seaplanes of areas of sea from which American warships might threaten his ships. While the Japanese Navy planners had been confident that the Americans would not learn of the Japanese presence until their first aircraft struck Midway at dawn on 4 June, Admiral Nagumo was a cautious commander and it troubled him deeply that Japanese intelligence had provided him with no information on the whereabouts of the American aircraft carriers. The reduction of his battle strength, owing to the absence of Shokaku and Zuikaku, was also weighing on Nagumo's mind as his ships approached Midway.

Aboard his giant battleship Yamato , several hundred miles to the west of Midway, Admiral Yamamoto was monitoring American radio traffic on the Midway islands, and noted a sharply increased volume as his ships approached the islands. He was also aware of American reconnaissance aircraft sweeping the western approaches to Midway. All of this activity raised a real possibility that the Americans had become aware of the approach of Japanese forces and a need to alert Admiral Nagumo that his arrival might be expected. However, Yamamoto chose to maintain radio silence. Being unaware that the Americans already knew about the impending Japanese offensive against Midway, this course may well have appeared the correct one from Admiral Yamamoto's viewpoint, but it left Admiral Nagumo completely unaware that his carriers might be sailing into danger as they approached Midway from the north-west.