During the latter days of April and the month of May, Admiral King and his senior advisers had to deal simultaneously with two urgent naval matters: the huge and vitally important battles with Japanese naval forces in the Pacific and the no less vital war against the U-boat in the Atlantic.
The first and most urgent task in the Pacific was to prevent Japanese amphibious invasion of Port Moresby, New Guinea, thereby diminishing the threat to Australia and the line of communications between that continent and the United States. The second most urgent task was to thwart a Japanese amphibious operation in the central Pacific, believed to be an invasion of either Midway Island or Oahu in the Hawaiian chain or possibly Alaska or California.
In accordance with the plan to deal with the threat to Port Moresby, devised by King and Nimitz during their meeting in San Francisco, April 25 to 27, Nimitz deployed the carriers Lexington and Yorktown and supporting forces to the Coral Sea. On May 7, the Allied forces engaged a superior Japanese force composed of the carriers Shokaku and Zuikaku, the light carrier Shoho, and supporting forces. American carrier aircraft sank Shoho while Japanese carrier aircraft sank the modern destroyer Sims and damaged the fleet tanker Neosho. The next day, May 8, the American aviators severely damaged the carrier Shokaku, while the Japanese aviators severely damaged the carrier Lexington and hit the Yorktown. Shokaku limped back to Japan, but Lexington was so badly damaged that she was sunk (by the destroyer Phelps), as was the damaged tanker Neosho (by the destroyer Henley). Both sides lost numerous pilots and aircraft and incurred other heavy casualties.*
During the run-up to the Battle of the Coral Sea, on May 3, a light Japanese force occupied Tulagi in the Solomon Island chain, which the Allies had recently evacuated. Alerted to this new threat to the line of communications to Australia, on the following day, May 4, aircraft from the Yorktown hit the Japanese invaders, sinking a destroyer, a minelayer, and one transport. The Americans proclaimed a great victory, but it was nowhere near that. Moreover, the Americans soon learned from radio decrypts that the Japanese objective in the lower Solomons was to build an air base on the much larger adjacent island, Guadalcanal. Since a Japanese air base there would pose a grave threat to the line of communications, it was an operation that could not be allowed to proceed. Thus Admiral King had yet another developing problem to deal with in the South Pacific.
Before and after the Battle of the Coral Sea itself, American codebreakers worked feverishly to positively identify the objectives of an impending and larger Japanese amphibious operation in the central Pacific. From various radio decrypts, intelligence advisers to Nimitz in Hawaii concluded that the first and main objective was an invasion of Midway Island in preparation for an invasion of Hawaii, together with an invasion of the islands of Kiska and Attu in the Aleutian chain, to thwart American air attacks on the Japanese home islands. However, intelligence advisers to Admiral King in Washington insisted that the Japanese objective was “south,” probably an invasion of New Caledonia, which the Americans had recently reinforced. When further codebreaking information on May 17 and 18 pointed unequivocally to Midway and the Aleutians, King yielded to Nimitz’s intelligence and approved a decision to shift the damaged carrier Yorktown from the South Pacific to the central Pacific. After rushed repairs, she was to join the carriers Hornet and Enterprise and supporting forces to repel the Japanese at Midway.
To replace the carrier Lexington, lost in the Coral Sea, on May 21 Admiral King directed Atlantic Fleet commander Ingersoll to send the carrier Wasp and a destroyer division (nominally six destroyers) to the Pacific as rapidly as possible. Then attached to the British Home Fleet, Wasp had only just flown off a second load of aircraft to Malta and required a week’s refit at Norfolk. Three days later, on May 24, King notified the British that Wasp, the new battleship North Carolina, the “jeep” carrier Long Island (to be used to ferry aircraft), one heavy and one light cruiser, and a division of destroyers were to be shifted to the Pacific. However, none of these warships arrived in Hawaii in time for the Battle of Midway.*
Acting on further information from Navy codebreakers, Nimitz was able to deploy his three carriers in a clever ambush off Midway. In a remarkable victory on June 4, aircraft from these American carriers sank four fleet carriers of the Imperial Navy covering force (Akagi, Kaga, Soryu, Hiryu) and forced the Japanese to withdraw. The American ambush included a dozen submarines, one of which, Tambor, caused a collision between the cruisers Mikuma and Mogami. The latter limped home but American aircraft found and sank Mikuma. Japanese aircraft severely damaged the carrier Yorktown. The next day, June 5, one of sixteen Japanese submarines in the attack force, 1-168, torpedoed and sank Yorktown and the destroyer Hammann, which was assisting the crippled carrier. Secondary Japanese forces occupied the Aleutian islands Kiska and Attu.
Admiral King’s preoccupation with the Pacific, as the British sneeringly put it, resulted in two strategic naval victories of immense consequences within six months of Pearl Harbor. The loss of four fleet carriers and one light carrier, the damage to the fleet carrier Shokaku, and the loss of the cream of the Japanese naval air arm was a devastating setback to the Imperial Navy. With the return of the carrier Saratoga from repairs in the States and the transfer of the carrier Wasp from the Atlantic, Nimitz could deploy four fast carrier task forces, sufficient naval air power to counterbalance and hold at bay the remaining Japanese carrier forces. Hence the Japanese were no longer able to undertake big operations such as an invasion of Midway or Hawaii, which required a strong force of sea-based air. Nor were they able to capitalize on the occupation of Kiska and Attu.
The Japanese did not, however, relax pressures in the Pacific. They intensified efforts in New Guinea with an overland attack on Port Moresby, and in the Solomon Island chain, areas where land-based aircraft could provide the Japanese the requisite air umbrella. One month after the Battle of Midway, on July 6, the Japanese landed two construction battalions (2,571 soldiers) on Guadalcanal to commence work on the air base. Owing to a new—and blinding—increase in the complexity in the latest variation of Japanese naval code JN-25, American code-breakers were unable to forewarn of this new Japanese landing. The first solid information on it came from Australian coast watchers hiding out in the Solomons.
The sudden and unexpected appearance of Japanese construction forces on Guadalcanal came as a shock to the Americans. It forced them to enlarge a planned attack on Tulagi and Florida islands (Watchtower) to include the capture of Guadalcanal and to push the timetable forward to the earliest possible date. Commanded by Admiral Robert L. Ghormley (who had been replaced in London by former Chief of Naval Operations Admiral Stark), on August 7, American and Australian naval forces simultaneously landed elements of the 1st Marine Division on Guadalcanal and Tulagi. Although caught by surprise, the Japanese reacted swiftly and effectively. They counterattacked the Allies with strong air and naval forces and sent a steady stream of infantry to drive the American Marines from Guadalcanal.
Neither Washington nor Tokyo had planned for a decisive battle in the Solomon Island chain. However, the struggle for Guadalcanal was to grow into one, dominating all other Allied and Axis operations in the Pacific for the remainder of 1942. The desperate fighting in the air and on the seas and in the jungles was to result in ghastly casualties on both sides and—ultimately—yet another legendary Pacific victory for the Americans.