Battle of the Coral Sea Begins in Pacific War

Context

Following the rapid Japanese conquests of early 1942 that secured much of Southeast Asia and the western Pacific, Imperial planners sought to strengthen their southern defensive perimeter. Operation Mo aimed to seize Port Moresby on the southern coast of New Guinea and Tulagi in the Solomon Islands, positions that would extend Japanese air coverage over northern Australia and threaten Allied supply routes across the South Pacific.

U.S. Navy cryptanalysts in OP-20-G had made substantial progress against the Japanese naval cipher JN-25B, reading up to 85 percent of traffic by late April. Intercepts revealed the timing and objectives of Operation Mo, allowing the Allies to concentrate available carriers in the Coral Sea rather than react after the landings had occurred.

What Happened

On 3 May, Japanese marines landed unopposed on Tulagi after the small Australian garrison withdrew. The next day, aircraft from the carrier Yorktown struck the supporting Japanese vessels, sinking a destroyer and several minesweepers and damaging others. Vice Admiral Shigeyoshi Inoue, commanding the Fourth Fleet and overall Operation Mo, responded by ordering his two fleet carriers, Shōkaku and Zuikaku, southward to hunt the American task force.

Rear Admiral Frank Jack Fletcher’s Task Force 17, built around Yorktown and Lexington, maneuvered through the Coral Sea for several days without the fleets sighting one another. On 7 May, U.S. planes located and sank the light carrier Shōhō. Japanese aircraft in turn damaged the oiler Neosho and destroyer Sims. The following day, both sides launched large strikes that damaged Shōkaku and left Lexington critically wounded by fires and flooding; the American carrier was scuttled that evening.

Aftermath

With air cover for the invasion force compromised by the loss of Shōhō and damage to Shōkaku, Inoue ordered the Port Moresby landing group to withdraw. Both sides recorded roughly equal aircraft losses, but the Japanese suffered heavier pilot casualties and the temporary removal of two fleet carriers from Yamamoto’s order of battle.

The battle ended with the Japanese holding a narrow tactical edge in ships sunk, yet the strategic initiative in the southwest Pacific had passed to the Allies for the first time since Pearl Harbor.

Legacy

Coral Sea established the carrier task force as the dominant striking arm of modern navies and demonstrated that battles could be decided beyond visual range. The damage inflicted on Shōkaku and the heavy attrition of Zuikaku’s air group kept both vessels out of the Battle of Midway the following month, materially aiding the American victory there.

Historians view the engagement as the first check on Japan’s unchecked expansion and a prototype for the carrier-centric campaigns that defined the remainder of the Pacific War.