A first step in Japanese high command’s defensive belt strategy was an advance into the southeast Pacific in order cut the line of communication and supply between the United States and Australia. At the same time, the central Pacific island of Midway was to be seized in order to anchor the left flank of the Gilbert Islands and to forestall direct American advances toward the Japanese homeland. While offensive in appearance, these campaigns were actually defensive in strategic tone. Their goals were to complete a defensive belt which the allies would find impregnable.
The Battle of Coral Sea took place in May 1942. If the Japanese had succeeded at Coral Sea, the way would have been open for the Japanese to have captured New Guinea and leave Australia isolated from Allied help and more open to a Japanese attack. The Battle of Coral Sea was fought entirely by planes – no ship on either side made any visual contact with any enemy ship...The Japanese called off the invasion of Port Moresby fearing that the Americans still had the capacity to destroy many of their landing craft. In numerical terms, the Japanese came out best in the Battle of Coral Sea. The loss of the 'Lexington' was great and far outweighed the loss of the 'Shoho'. The Japanese lost 43 planes to the Americans 33. However, the battle is seen as an American victory simply because it stopped Japan doing what it had set out to do - capture Port Moresby and isolate Australia.
A major flaw in the Japanese Midway strategy was the complexity of the operation. The Japanese assembled an invasion force of over two hundred ships. The warship component for the combined Midway and Alaskan offensives included eleven battleships, eight aircraft carriers, twenty-three cruisers, and sixty-seven destroyers. Against this awesome armada, the Americans could only field three aircraft carriers (one still damaged from the Battle of the Coral Sea), eight cruisers, and fourteen destroyers. If the Japanese had concentrated their massive naval power and focussed it against the United States Pacific Fleet at Midway, instead of dispersing it in a wide arc between Alaska and Midway, Japan would almost certainly have overwhelmed and destroyed the much smaller American fleet.
As a result, when the Japanese started organizing their Midway operation, American cryptologists were able to read about 90 percent of their coded messages. Changing the naval code was a routine procedure in the Japanese fleet. The system was changed every six months to a year, its additives every month to six months and the tactical code every month.
Winston Churchill said of the Battle of Midway, "this memorable American victory was of cardinal importance, not only to the United States but to the whole Allied cause...At one stroke, the dominant position of Japan in the Pacific was reversed." And that is why Midway was among the most important battles of the war, for if the Japanese had prevailed—and the order of battle certainly suggests that they should have—consider what would have ensued.
Unfortunately for the Japanese, U.S. intelligence broke the Japanese naval code, and the Americans anticipated the surprise attack. Three heavy aircraft carriers of the U.S. Pacific Fleet were mustered to challenge the four heavy Japanese carriers steaming toward Midway. In early June, U.S. command correctly recognized a Japanese movement against Alaska's Aleutian Islands as a diversionary tactic and kept its forces massed around Midway. On June 3, the Japanese occupation force was spotted steaming toward the island, and B-17 Flying Fortresses were sent out from Midway to bomb the strike force but failed to inflict damage. Early in the morning on June 4, a PBY Catalina flying boat torpedoed a Japanese tanker transport, striking the first blow of the Battle of Midway.
The Battle of Midway enabled the U.S. Navy to go onto the offensive. Herein lay the importance of the battle. For this is where I think people are wrong when they say that the loss of the battle would not have been a too important event. If the U.S. had indeed lost all three carriers at Midway there would have been merely three carriers remaining to oppose any Japanese move -- none of which was a really good ship. Saratoga was old and slow in maneuvering, Wasp small and with a small complement of planes, and Ranger slow and small as well as ill-protected. None of these carriers could hope to last in a battle with the Japanese carrier fleet which would allow the Japanese to prosecute several goals: construction of airfields on Guadalcanal; invasion of Port Moresby; invasion of New Caledonia; and more. The Battle of Midway reversed this. The Japanese could never again operate offensively, while the Americans could now do so at places of their own choosing.
At the Battle of Midway, Nagumo's near-perfect record finally saw an end. With a combination of reasons such as Admiral Osami Nagano's insistence of a simultaneous Aleutian operation and Yamamoto's overly-complex fleet operations, Nagumo saw a devastating loss of four fleet carriers at the conclusion of the battle.
Yamamoto's plan for the attack on Midway was complex and relied on perfect timing and diversionary tactics to lure parts of the American force away from Yamamoto's main battle fleet. It also required that four out of Japan's eight aircraft carriers were in the vicinity. The Japanese fleet also included the biggest battleship in the world, the 'Yamato' the smaller battleships 'Nagato' and 'Mutsu', and numerous cruisers and destroyers. Yamamoto's plan was ingenious but too intricate. It also contained two defects:
1) Yamamoto believed in the supremacy of the battleship. He failed to realise that an aircraft carrier could deliver a massive blow to the enemy but at a much greater distance than a battleship could. Yamamoto saw the aircraft carrier as supporting the battleship rather than the other way round. His huge battleships were also slower than any other warship he had and the rest of his fleet had to sail at a pace that suited the battleships.
2) Far more fatal to Yamamoto was the fact that the Americans knew his course of action. Admirals Spruance and Fletcher had their ships waiting for an attack and Yamamoto's plan to lure American ships away from their main body clearly would not work if the Americans knew that this was his intent.
The American victory in June 1942 Battle of Midway has been described so many times that it need not be retold here. But one series of events has barely been discussed at all. It gave information to the Japanese that might have prevented the U.S. Navy's victory from being even greater. A second event, related to the first, was the perpetration of war crimes on the three captives. Neither o these happenings came to light until nearly five years after the battle itself.