For four days in May 1942, Allied and Japanese aircraft carriers engaged each other off the coast of northern Australia in what experts have called the first modern naval engagement in history. The Battle of the Coral Sea was the first time enemy aircraft carriers had engaged in conflict, all without ever falling in each other’s sights. Beyond its groundbreaking status in the history of military technology, the battle also marked the first time since the start of World War II that the Allies halted a major Japanese advance. Although the Japanese did gain a tactical victory, the damage their navy sustained would have a direct effect on their loss at the Battle of Midway.
In the months following the attack on Pearl Harbor in December 1941, the Japanese navy continued to advance into the Pacific. By the spring of 1942, the Allies had not been able to stop them, but had been able to break the code the Japanese were using to communicate. On March 28, US Naval Intelligence officers intercepted a message that read, “THE OBJECTIVE OF MO WILL BE FIRST TO RESTRICT THE ENEMY FLEET MOVEMENTS AND WILL BE ACCOMPLISHED BY MEANS OF ATTACKS ON THE NORTH COAST OF AUSTRALIA.”
Operation MO was the Japanese plan to capture and occupy Port Moresby, the capital of the Australian territory of New Guinea. Once the city was occupied, they would set up a naval base and work to cut lines of communication between Australia, New Zealand, and the US. Once the Allies learned of this plan, they began sending their available strike forces to the Coral Sea, the body of water between New Guinea, Australia, and the Solomon Islands that had already fallen into Japanese hands.
Operation MO was part of a larger plan. The Imperial Navy was already planning to lure the American fleet into an ambush by invading Midway Atoll, but they eventually agreed that it would be advantageous to take Port Moresby first. In order to do that, they needed to take Tulagi, a small island in the Solomons. From there, they could send patrols into the Coral Sea that would protect the Moresby invasion force.
As the Japanese began their occupation of Tulagi, the Allies prepared for a fight. The aircraft carrier USS Yorktown arrived in the area on May 4 and launched aerial attacks that successfully sank and damaged several Japanese warships. The attacks weren't enough to halt the invasion, but they did key damage to the Japanese fleet. Now that they were aware of Allied presence in the area, the Japanese Carrier Strike Force headed for the Coral Sea.
In the Coral Sea, the Japanese forces met two US Navy task forces, which included the Yorktown and its fellow fleet carrier the USS Lexington, as well as a US-Australian cruiser force. The conflict lasted several days. For the first time in military history, the opposing ships never sighted each other. All of the attacks came from planes launched from the aircraft carriers. None of the ships ever fired on one other.
The Battle of the Coral Sea came to an end on May 8, 1942, when the Allies were forced to leave the combat area. The Lexington, USS Sims, and USS Neosho had sunk, and Yorktown was badly damaged. This led the Japanese to claim victory, but the Allied forces had inflicted damage that would prove to be vitally important.
On May 7, US aircraft spotted the Japanese light carrier Shoho, which was escorting an invasion screening force headed for Port Moresby. A miscommunication led the Allied forces to believe the screening force was the main invasion force, so all available aircraft were launched to stop it. The Allies successfully sunk the Shoho, and the Japanese forces had to turn back.
Even after the Allies retreated, the Japanese air forces were too damaged to continue the invasion. For the first time since the start of WWII, the Japanese advance had been checked. Port Moresby remained in Allied hands.
In addition to the 70 warplanes the Japanese lost during the Battle of the Coral Sea, several of their aircraft carriers were badly damaged. As a result, both Shokaku and Zuikaku carriers were unable to participate in the Battle of Midway less than a month later. This reduced the number of Japanese aircraft carriers at Midway by a third.
In June 1942, the Battle of Midway would prove to be one of the most decisive moments of World War II. The Allied victory there turned the tide of the war in the Pacific. In a way, it’s fitting that the USS Yorktown, repaired from the damage it sustained in the Coral Sea, played a major role in defeating the Japanese at Midway. The victory at Midway was a shining moment for the Allies in the war, but it might not have occurred without their strategic moves during the Battle of the Coral Sea.