In 1924, the Coast Artillery adopted a regimental organization, and the Regular Army's 8th Coast Artillery Regiment was formed at Fort Preble. A reserve regiment to supplement the regular forces in wartime was also formed, the 240th Coast Artillery of the Maine National Guard. Both of these regiments garrisoned the Harbor Defenses of Portland during early World War II, in which Fort Preble was a naval net depot for net laying ships and a control station for the Casco Bay degaussing range. All remaining mortars were scrapped in 1942; Fort Preble was superseded by new defenses centered on Battery Steele on Peaks Island. Only one 3-inch gun remained, which was removed in 1946.