As World War II began, the Samoa islands were an essential link in the chain of communications between the United States, Australia, and New Zealand, a sea lane that also ran through the Fiji island. Holding the line drawn from Midway to Samoa, Fiji, and Brisbane against the Japanese was considered essential. The loss of these islands would have effectively cut off communications between the west coast of the United States and Australia. The Samoa islands played an important role by protecting these trade routes and to safeguard communication links to the south.
With the Pearl Harbor attack, the governor/commandant assumed direct control of all construction work in progress on Tutuila and rechanneled the efforts into defense of Pago Pago Harbor and the immediate vicinity, particularly bombproof shelters. American Samoa was touched by enemy fire only once. On January 11, 1942, the Naval Station was shelled by a Japanese submarine. One shell, an odd stroke of irony, struck the home and store of one of the very few Japanese residents of the island. Another struck the Navy Dispensary, doing only minor damage, but most of the shells landed in the bay. At the time, of course, the incident must have seemed to be only the beginning. This was the only enemy attack in American Samoa.
On January 20, 1942, the Marine Brigade arrived with 5,600 officers and enlisted men with their heavy artillery to defend the island. Natives were also recruited to form a Samoan Marine Brigade known as (Maligi Samoa) that consisted of 350 men. Tutuila island became the largest jungle training center in the South Pacific. The Battle of the Coral Sea in the Pacific was the turning point of the war, when the Japanese lost so many of their men and war ships by the Americans.
Orders were given to begin the dismantling of the war effort in the Samoa Group in February 1944. By the summer of 1945 the Naval Station had reverted to its peacetime status as a permanent base. Its purpose as such included limited anchorage facilities, a fueling station, a minor repair depot, supply and communication facilities, and a weather station.