In spring 1942 the Japanese naval high command confronted a strategic dilemma. Ironically, the difficulty stemmed from the spectacular success Japanese arms had enjoyed in the war to date. The aim in December 1941 had been, first, to occupy Southeast Asia and the East Indies and, second, to establish an island perimeter shielding this “Southern Resources Area and the Home Islands from the inevitable U.S. counteroffensive. The Japanese had accomplished these conquests in approximately half the time anticipated. For practical purposes, the Imperial Navy had run out of plans.
Five options came under consideration. The most grandiose envisioned an offensive into the Indian Ocean and the capture of Ceylon, leading to an eventual linkup with European Axis forces somewhere in the Middle East. This dream dissipated with the army’s refusal to provide the five divisions needed to seize Ceylon. The army also declined to furnish the requisite manpower for the occupation of all or part of Australia. A third possibility, that of going on the defensive, was predictably rejected. Support of the two remaining options reflected a dangerous division in the navy’s command. The planning section of the Naval General Staff advocated a deeper thrust into the Southwest Pacific to isolate Australia from the United States. The operation, for which the army agreed to release troops, would commence with the seizure of Port Moresby—the Allied base on the southeastern coast of New Guinea and Tulagi in the Solomon Islands and culminate in the occupation of New Caledonia, the Fijis, and Samoa. The opposing view, championed by Admiral Isoroku Yamamoto, Commander-in-Chief of the Combined Fleet, called for a return to the Central Pacific with the aim of capturing Midway Atoll and forcing a battle in which the enemy carriers absent from Pearl Harbor on 7 December 1941 could finally be destroyed.
In theory, the responsibility for shaping a new strategy belonged to the Naval General Staff, and Imperial General Headquarters duly approved its proposal on 13 March 1942. Days later, the Combined Fleet unveiled its very different plan, to which the Naval General Staff raised intelligent objections. Yamamoto then laid his enormous prestige on the line by threatening to resign unless the Naval General Staff adopted the fleet’s plan. On 5 April, the staff folded. The Midway offensive (Operation MI) would be launched in June. Yet the first phase of the Southwest Pacific offensive, the seizure of Port Moresby and Tulagi (Operation MO), was allowed to go forward, with limited resources, in May.
Of all the decisions the navy’s leaders could have reached, this was by far the worst. The apparent ease with which victory had been heaped upon victory caused them to forget that, with only six fleet carriers (plus five smaller types) in commission, the Imperial Navy lacked the luxury of a margin for error. To hazard a portion of the carriers needed for the Central Pacific offensive in a secondary operation in the Southwest Pacific was to jeopardize the success of both. Afterward the navy coined a phrase to describe the overconfidence that ruled in its councils: “victory disease.” Not everyone succumbed. Despite the decision of 5 April, some members of the Naval General Staff continued to resist a return to the Central Pacific—up to the time of the Halsey-Doolittle Raid. Thereafter it was impossible to oppose an operation that promised to spare the navy the shame of seeing more U.S. bombers in Japanese skies.
“Victory disease” also facilitated the work of the U.S. Navy’s signals intelligence activities, Operation Magic. The Japanese naval code U.S. cryptanalysts called JN-25b was scheduled to be changed on 1 April. Had this been done, the U.S. codebreaking effort would have been set back to square one. In any event, difficulties in distributing new codebooks led the Japanese to postpone the change to 1 May and then, even more complacently, to 1 June. These delays enabled U.S. analysts to penetrate enemy signals security until eventually they could read 85% of some messages.
On 9 April, Magic picked up the first indication that the Japanese were planning a new advance into the Southwest Pacific. Subsequent intercepts confirmed this finding, and between 17 and 22 April, Admiral Chester W. Nimitz, Commander-in-Chief, Pacific Fleet, held a series of staff meetings to shape the U.S. response. Intelligence estimated that the enemy would commit three fleet carriers and one light carrier to the operation, the primary objective of which must be Port Moresby.
Upon learning that the Enterprise (CV-6) and Hornet (CV-8) were returning safely from the Halsey-Doolittle Raid, Nimitz ordered the Lexington (CV-2), the only other U.S. carrier in the Central Pacific, to join the Yorktown (CV-5), the only one then in the Southwest Pacific. The Enterprise and Hornet would follow. Of course, the battle might not await their arrival, but this was a risk—long with that of denuding the Central Pacific of carriers—that Nimitz was ready to accept.
The ensuing engagement—known to history as the Battle of the Coral Sea—did, in fact, take place before the Enterprise and Hornet could reach the scene. Allied forces present consisted of the Yorktown's Task Force (TF)-17, under Rear Admiral Frank Jack Fletcher, who also held overall command; the Lexington's TF-11, commanded by Rear Admiral Aubrey W. Fitch; and TF-44, a U.S. and Australian cruiser-destroyer force under Rear Admiral J. C. Crace, Royal Navy. On 6 May, Fletcher combined these formations into an enlarged TF-17, the components of which were divided into five task groups. The Japanese order of battle, characteristically complex, included two landing forces, one for Tulagi and another for Port Moresby, each with its own support force; a separate Main Body Support Force containing the light carrier Shoho; and a Carrier Striking Force under Vice Admiral Takao Takagi formed around the fleet carriers Shokaku and Zuikaku—one fewer than U.S. intelligence had estimated would be deployed. Responsibility for the conduct of the operation as a whole belonged to Vice Admiral Shigeyoshi Inoue.
The extraordinarily complicated course of the battle can only be sketched here. On 3 May the Japanese seized undefended Tulagi. The next day Fletcher sent the Yorktown's aircraft to attack enemy vessels off the island, where they sank a destroyer-transport and three smaller craft. Bad weather and worse luck combined to frustrate the opposing forces’ attempts to locate one another on 5 and 6 May. On the 7th the Japanese happened on Fletcher’s little oiler group, consisting of the fleet oiler Neosho (AO-23) and the destroyer Sims (DD-409), and finished them both. For their part, U.S. forces discovered the Main Body Support Force and smothered the Shoho with 20 bomb and torpedo hits. Not until the morning of 8 May did the two carrier forces finally make contact.
Initially, the first exchange of strikes appeared to be entirely in TF-17’s favor. The Zuikaku emerged unscathed, but the Shokaku suffered hits from three bombs that left her unable to launch or recover aircraft, effectively putting her out of action. The Yorktown suffered moderate damage from one direct hit and several near misses, and the Lexington, although struck by two torpedoes and at least two bombs, did not seem to have been hurt too badly. An hour later, however, she was wracked by the first of a succession of internal, aviation gasoline explosions that led to the decision to sink her.
By then, the Battle of the Coral Sea was over. Neither side launched a second strike. The Carrier Striking Force had lost 77 of its original 108 operational aircraft, and despite his pilots’ claims to have sunk both U.S. carriers, Admiral Takagi chose to retire. This decision, coupled with the loss of the Shoho and her 15 planes, meant that no carrier aircraft remained to cover the Port Moresby landing force or support its assault. Admiral Inoue therefore canceled the execution of Operation MO. At midnight, Yamamoto ordered Takagi to renew the engagement, but it was too late. With the Lexington gone, the welfare of the Yorktown necessarily became Fletcher’s chief concern, and he had withdrawn.
Strategically, Coral Sea was unquestionably a U.S. victory. For the first time in the war, Japanese forces had failed to achieve an important objective. Tactically, the battle is often regarded as a Japanese victory. The statistics support this view; the 12,000-ton Shoho was hardly a fair trade for the 33,000-ton Lexington, and altogether the Imperial Navy sank more than twice the tonnage that it lost. Yet in the tide of war these statistics counted less than the fact that the battle temporarily deprived the Imperial Navy of one-third of its fleet carriers. When the Combined Fleet sortied on its Central Pacific offensive, the Shokaku and Zuikaku remained behind, the former still undergoing repair and the latter awaiting a replacement for her shattered air group. They would be sorely missed at Midway.
For further reading: John B. Lundstrom, The First South Pacific Campaign (Annapolis, MD: Naval Institute Press, 1976); Bernard A. Millon. trans. S. V. Whitley, The Battle of the Coral Sea (Annapolis, MD: Naval Institute Press, 1974); H. P. Willmott, The Barrier and the Javelin (Annapolis, MD: Naval Institute Press, 1983).