The citadel was designed with open gun emplacements on the north, east and west sides. As its defensive role came to an end, by 1903 the citadel had become an infantry barracks. During World War I and II, the Verne became the Headquarters of Coast Artillery. During World War II, a Chain Home Low Radar set was installed within the citadel, and the main magazine became a hospital. After the war, the last military use of the fort was by the Royal Engineers.