 The armor protecting both the main armored belt amidships and the main battery turrets was 270 mm ( 10 @.@ 6 in ) thick . The lower armored deck was 20 mm ( 0 @.@ 79 in ) thick , with 50 mm ( 2 @.@ 0 in ) of armor plating on the sloped sides . The casemate guns were protected with 180 mm ( 7 @.@ 1 in ) of steel armor . The ships were also equipped with a 20 mm thick torpedo bulkhead . 
