An appraisal of the strategic situation in the Coral Sea in February 1942

As early as August 1941, the Japanese Navy had requested troops from the Japanese Army to capture Rabaul in the Australian Territory of New Guinea at an early stage of the Pacific War. Rabaul possessed a fine harbour and was located on the northern island of New Britain. The admirals of the Imperial Navy General Staff viewed Rabaul as a threat to Japan's major naval base at Truk in the Caroline Islands. The reason for their concern was that Truk would be well within the operational range of American B-17 heavy bombers if they were based at Rabaul.

The force earmarked for the capture of Rabaul was Japan's South Seas Detachment. This was an elite 5,000-man unit with specialist jungle training. This was the same force that had captured America's Guam on 10 December 1941.

On 23 January 1942, five thousand troops of the South Seas Detachment stormed ashore at Rabaul and quickly overran the single reinforced Australian battalion defending the town and its harbour. Having occupied Rabaul, the Japanese were greatly concerned when their invasion force immediately came under attack from Allied bombers launched from Lae and Salamaua on the north-eastern coast of the New Guinea mainland. Something now had to be done to protect Rabaul from Allied counter-attacks. Plans were immediately set in train for the early capture of Lae and Salamaua.

While the Japanese were preparing to occupy more of the island of New Guinea, Admiral Nimitz had not been idle at Hawaii. He responded to the capture of Rabaul by ordering Vice Admiral Wilson Brown to take Task Force 11 (TF-11), formed around the heavy fleet carrier USS Lexington (CV-2), to the Coral Sea to raid Rabaul.

With its supporting cruisers and destroyers, Lexington moved into the Coral Sea and approached Rabaul from the south-east. A Japanese patrol plane spotted the American task force on the morning of 19 February, and Lexington was attacked later that day by a formation of eighteen Japanese medium bombers launched from Rabaul. All but two of the Japanese bombers were shot down by Wildcat fighters from Lexington. This was the famous occasion when Lieutenant Edward "Butch" O'Hare shot down five Japanese bombers and was awarded the Medal of Honor. Having lost the advantage of surprise, Admiral Brown decided to withdraw his task force out of range of Japanese bombers.

The proximity of an American carrier task force so close to Rabaul produced consternation at Rabaul and Truk, and caused the Japanese to postpone the capture of Lae and Salamaua until 8 March 1942.

This was the situation unfolding in the South Pacific that had caused Admiral King to divert Yorktown to the Coral Sea on 14 February. An additional carrier had been requested by Vice Admiral Brown to support Lexington in a raid on shipping at the Japanese naval base being developed at Rabaul.

Yorktown is ordered to join Lexington in the Coral Sea

On 24 February 1942, Admiral Nimitz ordered Rear Admiral Fletcher's Task Force 17 (TF-17) to rendezvous in the Coral Sea with Vice Admiral Brown's Task Force.

As Yorktown and her escort warships were steaming towards the Coral Sea, Admiral Brown was directed to use his combined task forces to attack Japanese-occupied areas on New Britain about 10 March. The purpose of these raids was to check the Japanese advance southwards and to cover the arrival of an American troop convoy at Noumea in New Caledonia. On 6 March, the Yorktown task force joined Vice Admiral Brown's TF-11 and Rear Admiral Crace's Anzac cruiser squadron in the Coral Sea. The combined Allied force, under the overall command of Vice Admiral Brown, was now designated task Force 11 (TF-11). Admirals Brown, Fletcher and Crace immediately began planning for attacks on Rabaul and the airfield at Gasmata on the southern coast of New Britain.