During World War II, the post was put to use as a training facility and supply depot. and as a look-out for German U-boats and planes. On 7 December 1941, the fort was listed as manned by the 242nd Coast Artillery Regiment (Harbor Defense) of the Connecticut Army National Guard. Today, on the east side of Plum Island, a network of trenches remains from the area's tenure as an artillery post. Fort Terry's guns were superseded by the pair of 16-inch batteries at Camp Hero in Montauk by 1944, so all except the four 3-inch guns of Batteries Eldridge and Dalliba were scrapped.