In early May 1942,  Japanese forces invaded and occupied Port Moresby in New Guinea and Tulagi in the southeastern Solomon Islands.

From May 4-8, 1942  the Imperial Japanese Navy engaged in a major aircraft battle with naval and air forces of the United States and Australia. The resulting Battle of the Coral Sea was the first time that enemy aircraft carriers engaged each other (although ships on neither side actually sighted or fired directly upon the other).

Although Japanese aircraft sank more Allied ships than vice versa, overall, the Battle of the Coral Sea marked the first reversal of Japanese advances in the Pacific War and is regarded as a strategic victory for the Allies. Perhaps most importantly, the Japanese fleet carriers Shōkaku and Zuikaku were seriously damaged and would be unable to participate in the upcoming June Battle of Midway.