The Battle of the Coral Sea
May 4, 1942 – The battle of the Coral Sea, a four-day naval battle between the Imperial Japanese Navy (IJN) and the Allied naval and air forces of the United States and Australia, begins. This action is historically significant as the first action in which aircraft carriers engaged each other, as well as the first in which the opposing ships neither sighted nor fired directly upon one another and as the first blockage of the steady Japanese advance since Pearl Harbor six months earlier.
In an attempt to strengthen their defensive position in the South Pacific and control the Coral Sea, the Japanese decided to invade and occupy Port Moresby (in New Guinea) and Tulagi (in the southeastern Solomon Islands). The plan to accomplish this was called Operation MO and involved several major units of Japan’s Combined Fleet. These included two fleet carriers and a light carrier to provide air cover for the invasion forces. Japanese forces were under the overall command of Japanese Admiral Shigeyoshi Inoue.
The U.S. learned of the Japanese plan through signals intelligence and sent two United States Navy carrier task forces and a joint Australian-U.S. cruiser force to oppose the offensive. These were under the overall command of U.S. Admiral Frank J. Fletcher. On 3–4 May, Japanese forces successfully invaded and occupied Tulagi, although several of their supporting warships were sunk or damaged in surprise attacks by aircraft from the U.S. fleet carrier Yorktown. Now aware of the presence of U.S. carriers in the area, the Japanese fleet carriers advanced towards the Coral Sea intending to locate and destroy the Allied naval forces. On the evening of 6 May, the direction chosen for air searches by the opposing commanders brought the two carrier forces to within 70 nmi (81 mi; 130 km) of each other, unbeknownst to both sides. Beginning on 7 May, the carrier forces from the two sides engaged in airstrikes over two consecutive days. On the first day, both groups mistakenly believed they were attacking their opponent’s fleet carriers but were actually attacking other units, with the U.S. sinking the Japanese light carrier Shōhō while the Japanese sank a U.S. destroyer and heavily damaged a fleet oiler (which was later scuttled). The next day, the fleet carriers found and engaged each other, with the Japanese fleet carrier Shōkaku heavily damaged, the U.S. fleet carrier Lexington critically wounded (and later scuttled), and Yorktown damaged. With both sides having suffered heavy losses in aircraft and vital aircraft carriers damaged or sunk, the two forces disengaged and retired from the battle area. Because of the loss of carrier air cover, Inoue recalled the Port Moresby invasion fleet, intending to try again later, but never did.
Although a tactical victory for the Japanese in terms of ships sunk, the battle would prove to be a strategic victory for the Allies for several reasons. The battle marked the first time since the start of the war that a significant Japanese advance had been checked by the Allies. More importantly, the Japanese fleet carriers Shōkaku and Zuikaku—the former damaged and the latter with a depleted aircraft complement—were unable to participate in the Battle of Midway the following month, while Yorktown did participate, ensuring a rough parity in aircraft between the two adversaries and contributing significantly to the U.S. victory in that battle. The severe losses in carriers at Midway prevented the Japanese from reattempting to invade Port Moresby from the ocean and helped prompt their ill-fated land offensive over the Kokoda Track. Two months later, the Allies took advantage of Japan’s resulting strategic vulnerability in the South Pacific and launched the Guadalcanal Campaign; this, along with the New Guinea Campaign, eventually broke Japanese defenses in the South Pacific and was a significant contributing factor to Japan’s ultimate surrender in World War II.
The US/Australian forces had 1 fleet carrier damaged then scuttled, 1 destroyer sunk, 1 oiler sunk, 1 fleet carrier damaged, 69 aircraft destroyed, and 656 killed. The Japanese lost 1 light carrier sunk, 1 destroyer sunk, 3 small warships sunk, 1 fleet carrier damaged, 1 destroyer damaged, 1 smaller warship damaged, 1 transport damaged, 92 aircraft destroyed and 966 killed.