By mid-1942, the Japanese found themselves holding a vast area from the Indian Ocean to the Central Pacific, even though they lacked the resources to defend or sustain it. Moreover, Combined Fleet doctrine was inadequate to execute the proposed "barrier" defence. Instead, Japan decided on additional attacks in both the south and central Pacific. While she had the element of surprise at Pearl Harbor, Allied codebreakers had now turned the tables. They discovered an attack was planned against Port Moresby; if it fell, Japan would control the seas to the north and west of Australia and could isolate the country. The carrier USS Lexington under Admiral Fletcher joined USS Yorktown and an American-Australian task force to stop the Japanese advance. The resulting Battle of the Coral Sea, fought in May 1942, was the first naval battle in which ships involved never sighted each other and only aircraft were used to attack opposing forces. Although Lexington was sunk and Yorktown seriously damaged, the Japanese lost the carrier Shōhō, and suffered extensive damage to Shōkaku and heavy losses to the air wing of Zuikaku, both of which missed the operation against Midway the following month. Although Allied losses were heavier than Japanese, the attack on Port Moresby was thwarted and the Japanese invasion force turned back, a strategic victory for the Allies. The Japanese were forced to abandon their attempts to isolate Australia. Moreover, Japan lacked the capacity to replace losses in ships, planes and trained pilots.

What American carrier joined the USS Yorktown to stop the Japanese attack on Port Moresby in 1942?