3 May 1942
In early 1942, advancing Japanese forces began examining the possibility of capturing:
- Port Moresby
- Tulagi
- New Caledonia
- Fiji
- Samoa.
The occupation of Port Moresby would cut off the eastern sea approaches to Darwin. It would also provide the Imperial Japanese Navy with a secure operating base on Australia's northern doorstep.
The Japanese plan was to initially seize the islands of Tulagi, in the Solomons, and Deboyne, off the east coast of New Guinea. The force that would move to occupy Port Moresby would wait until Tulagi was captured on 3 May before sailing from Rabaul. Entering the Coral Sea from the north, the force bound for Port Moresby was covered by the Carrier Striking Force. It would enter the Coral Sea from the direction of the Solomon Islands in the north-east.
The Allied response was based on 2 carrier task forces centred on US Ships Lexington and Yorktown. The Allied cruiser force, Task Force 44, was commanded by an Australian-born Royal Navy officer serving in the Royal Australian Navy, Rear Admiral John Crace, RN. The force included HMA Ships Australia (II) and Hobart (I).
After the Japanese landed at Tulagi on 3 May, carrier-based US aircraft launched a series of air raids on Japanese shipping in the harbour. On the morning of the 7th, Japanese aircraft located and sank an American destroyer and damaged an oiler.
Over the following 2 days, the American and Japanese fleets fought an engagement unique in naval history. It was the first major engagement in which surface vessels neither sighted each other nor exchanged a single shot. All offensive action was carried out by embarked aircraft.
Early on the morning of 7 May, Task Force 44 was detached to cover the Jomard Passage and intercept the invasion force heading for Port Moresby. That afternoon, the cruiser force came under repeated air attack. However, it was able to repel the Japanese aircraft with only a small number of casualties. The returning Japanese aircraft reported that they had encountered a force of battleships.
This inaccurate battle report prompted the Japanese to reverse the course of the Moresby invasion fleet until the situation regarding ‘battleships’ was clarified. Had Crace’s ships been with the main Allied carrier fleet, the Japanese invasion force would have been able to proceed to Port Moresby unmolested.
The Battle of the Coral Sea may be seen as a Japanese tactical victory, but an Allied strategic victory. Allied losses were greater, but the invasion of Port Moresby had been stopped. More so, the seemingly relentless Japanese advance had stalled. The battle also severely reduced the number of carriers and aircraft available to the Japanese at the pivotal Battle of Midway in June.