Key point: The seemingly inconclusive battle was a turning point for the Allies.
In the first five months of the Pacific War, the Imperial Japanese military won an almost uninterrupted string of victories, seizing Burma, Indonesia, the Philippines, Singapore, and most of the Solomon Islands and New Guinea. However, Australia remained a thorn in Japan’s southwestern Pacific flank—one which needed to be cut off from U.S. reinforcements before Japanese troops could invade.
Though Adm. Isoroku Yamamoto planned on drawing U.S. carriers into a decisive battle around Midway Island in June 1942, he first authorized Operation Mo in April to isolate Australia by dispatching two separate invasion fleets to seize Tulagi (part of the Solomon Islands) and Port Moresby, a key supply point for Australian troops on New Guinea.
However, American cryptographers had broken the Japanese naval code and learned the details of the plan in a matter of days. Adm. Chester Nimitz decided to dispatch the Navy’s fleet carrier, the Lexington, and the more modern Yorktown to bushwhack the Japanese invasion force.
The American ships would confront a Japanese screening force that grew to include the fleet carriers Shokaku and Zuikaku as well as the light carrier Shoho, commanded by Adm. Takeo Takagi. The two opposing carrier groups mustered nearly the same number of aircraft: 127 to 128 bombers and fighters. The Lexington’s wing included thirty-five SBD Dauntless dive bombers, twenty-one F4F Wildcat fighters and twelve TBD Devastator torpedo bombers.