The Japanese activities on Tulagi and Guadalcanal were observed by Allied reconnaissance aircraft, as well as by Australian coastwatcher personnel stationed in the area.

In launching this war, Japanese leaders sought to neutralize the American fleet, seize possessions rich in natural resources, and obtain strategic military bases to defend their far-flung empire.

Inoue believed that the capture and control of these locations would provide greater security for the major Japanese base at Rabaul on New Britain.

Japan's Naval General Staff endorsed Inoue's argument and began planning further operations, using these locations as supporting bases, to seize Nauru, Ocean Island, New Caledonia, Fiji, and Samoa and thereby cut the supply lines between Australia and the U.S., with the goal of reducing or eliminating Australia as a threat to Japanese positions in the South Pacific.

[17] The only Allied military forces at Tulagi were 24 commandos from the Australian Army's 2/1st Independent Company, under Captain A. L. Goode, and about 25 personnel from 11 Squadron RAAF, under F/O R. B. Peagam, operating a seaplane base on nearby Gavutu-Tanambogo with four PBY Catalina maritime patrol aircraft.

In the belief that it might prevent them being executed for espionage, all of the coastwatchers were commissioned as Royal Australian Naval Volunteer Reserve officers, and they were directed by Lieutenant Commander Eric Feldt, who was located at Townsville in Australia.

[19] Throughout most of April, the Japanese conducted "desultory" bombing raids on Tulagi with aircraft based at Rabaul or nearby that caused little, if any, damage.

[21] Based on this intelligence, on 22 April, U.S. Admiral Chester Nimitz—stationed at Pearl Harbor—directed Allied forces towards the Coral Sea area to interdict the Japanese Mo operation.

That same day, Fletcher detached TF 11 to refuel, expecting to rejoin with Lexington and her escorts on 4 May at a predetermined location in the Coral Sea.

Later that day, coastwatcher D. G. Kennedy on New Georgia island sighted and reported a large Japanese force of ships heading towards the southern Solomons.

[23] Soon after, Goode and Peagam—anticipating that the Japanese would attack with overwhelming numbers—ordered the execution of a pre-planned evacuation operation and began the destruction and demolition of their equipment and facilities on Tulagi and Gavutu-Tanambogo.

The ship with the RAAF personnel spent the day with coastwatcher and protectorate District Officer Martin Clemens at Aola on Guadalcanal and departed that night.

[16][24] Supporting the Japanese landings were seaplanes from Kamikawa Maru, temporarily based at Thousand Ships Bay at Santa Isabel Island.

On 10 May, as Okinoshima participated in the first Japanese attempt to take Ocean (Banaba) and Nauru Islands, titled Operation RY, she was sunk by the submarine USS S-42 off New Ireland (05°06′S 153°48′E / 5.100°S 153.800°E / -5.100; 153.800).

[10][32][36] The lost Yorktown TBD aircrew (Leonard Ewoldt, pilot, and Ray Machalinsk gunner) reached Guadalcanal after drifting in the ocean for three days.

A Roman Catholic missionary, Father Jean Boudard, took them to Martin Clemens who arranged for a boat to take them to San Cristobal.

[40][41] After striking Tulagi, Yorktown rejoined with Lexington, and the two carriers engaged the rest of the Japanese forces involved in the Mo operation from 6–8 May in the Battle of the Coral Sea.

The next Japanese seaborne attempt to take Port Moresby, however, never happened, mainly because of their navy's defeat in June at the Battle of Midway.

The failure to take Port Moresby in May 1942 would have significant and far-reaching strategic implications, many of which involved the small Japanese naval base at Tulagi.

The two strategic victories for the Allies in the battles of the Coral Sea and Midway provided an opportunity to take the initiative and launch an offensive against the Japanese somewhere in the Pacific.

An Allied plan to attack the southern Solomons was conceived by U.S. Admiral Ernest King, Commander in Chief, United States Fleet.

He proposed the offensive to deny the use of the southern Solomon Islands by the Japanese as bases to threaten the supply routes between the U.S. and Australia, and to use them as starting points for a campaign.