United States Army Coast Artillery Corps troops were first deployed to Argentia in early 1941, at first a single coast defence battery with two or four 155 mm guns and an anti-aircraft battery. In January 1942 construction began on two batteries of 6-inch guns, and in March 1942 the United States Army established Fort McAndrew at Argentia to provide security to the navy base through an anti-aircraft battery and additional coast defence guns. Later that spring the Royal Navy established a small maintenance base at Argentia to service its ships involved in convoy escort groups operating out of Halifax, Sydney, St. John's and in the Gulf of Saint Lawrence.