Defense
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The surviving crew of USS Lexington, sunk by the Japanese in the Coral Sea, abandon ship. Sailors slide down ropes and are picked up by small boats; the destroyer, right, is picking up the sick and wounded.
The first few months of 1942 saw Japan take control of islands throughout the Central and South Pacific, including the Philippines and Guam, as part of its plan to form a defensive perimeter to protect its empire and blunt Allied counterattacks.
By mid-April, Tokyo was ready to turn its attention to Port Moresby in what is now southeastern Papua New Guinea and at Tulagi in the central Solomon Islands. Establishing air bases there would provide better defensive positions, put Japanese planes within range of Australia, and be jumping-points for further advances, which would allow Japan to secure more resources and to cut supply and communications lines between Australia and the US.
The Japanese campaign, called Operation Mo, took shape in April, with Japan planning to capture Tulagi in early May, followed by the seizure of Port Moresby about a week later. But the US Navy had penetrated Japanese codes and was able to glean details of the operation from Japanese naval movements.
By April, British and US intelligence had a general idea of where and when the attack would come. The US sent a two carriers to counterattack, setting up what would become the Battle of the Coral Sea - the first naval battle in which aircraft carriers engaged each other and the combatants did not come within sight of each other, yielding an Allied victory that set the stage for Japan's defeat.