The Harbor Defenses of the Delaware were previously Forts Delaware, DuPont, and Mott, all near Delaware City. They were sited well north in the Delaware estuary due to the short range of their guns. The long-range guns of Fort Saulsbury allowed an enemy to be engaged much further south. Fort Saulsbury consisted of Batteries Hall and Haslet, each with two 12-inch guns and a large ammunition and fire control bunker constructed of reinforced concrete and earth. Battery Hall was named for David Hall, a Revolutionary War officer and former Governor of Delaware. Battery Haslet was named for John Haslet, also a Revolutionary War officer, killed at the Battle of Princeton. Like the initial construction of similar batteries, the guns were in the open and would have been vulnerable to air attack. Apparently the fort's position back from the coast was thought to be sufficient concealment against attack from the sea. Unusually, Fort Saulsbury had no smaller guns sited near it, probably since it had no minefield requiring rapid-fire guns to defend against minesweepers. Both batteries were completed in 1920 but apparently not accepted for service until 1924, as most references give that date for their entry into service.