The ships were protected with Krupp armor. The main armored belt was thick in the central portion of the ship where it protected the ammunition magazines and propulsion machinery spaces. The deck armor was thick on the horizontal; its edges sloped down to connect to the lower edge of the belt to protect from shells that passed over the belt. The thickness of the slopes ranged from fore and aft and amidships, where the upper belt armor afforded another layer of protection. Above the main belt, the upper belt of 140 mm steel extended between the fore and aft main-gun turrets. Another strake of armor that was 140 mm thick protected the casemate guns at the main deck level. The casemate guns themselves received gun shields. The main battery turrets had 250 mm sides and thick roofs, while the secondary turrets had thick sides. The sides of the forward conning tower were thick and the roof was 50 mm thick, while the aft conning tower received significantly less protection, with 150 mm thick sides and a roof.