It coordinated the US Army coast defenses of Naval Station Argentia and the port of St. John's, Newfoundland from January 1941 to 8 September 1945.

[2][3] On 15 January 1941, Newfoundland Base Command was activated on board the United States Army troop transport ship USAT Edmund B. Alexander at the New York Port of Embarkation.

Although the harbor defense command was reportedly activated with the arrival of the 155 mm gun battery, it was on a small scale initially.

[1] On 27 March 1941 the United States officially signed the Lend-Lease agreement which gave possession of the site for Fort Pepperrell (initially Camp Alexander) near St. John's; construction work began in earnest on 15 April.

[11] During 1941 two Lend-Lease 10-inch M1888 disappearing guns were emplaced at Fort Cape Spear near St. John's; these were manned by Canadian forces.

On 7 December 1941 the United States entered World War II following the attack on Pearl Harbor.

Construction ramped up at US facilities in Newfoundland; for coast defense batteries this was primarily at Argentia.

These batteries had two 6-inch guns each, on shielded long-range carriages with reinforced concrete and earth bunkers housing magazines and fire control equipment.

If fully inactivated, possibly its functions and personnel were transferred to the harbor defense command.