Fortifications in the 19th century typically employed both casemate and barbette emplacements. Their lower casemates had between and of armor, and their upper casemate had of armor. It had armor on the front of the casemate and on the glacis plate. There are empty gun emplacements and an empty casemate. The hull space above the citadel was an armored casemate with plating. It was a modification of the 75mm 1929 casemate fortress gun. The casemate guns themselves received gun shields. The army designed the largest casemate (#1) as a barracks. C&R proposed secondary guns for these ships, protected by casemate armor. Her lower casemate had between of armor, and her upper casemate had of armor. The casemate armor was also thick. The fort also had a mine casemate to control a naval minefield. All three variants mounted their secondary guns in a casemate battery. The after casemate, hull, and deck not covered by the casemate were left unprotected. The lower edge of the casemate sat on top of ship's belt armour.