 The ships ' protection scheme consisted of compound armor . The Ruggiero di Laurias had an armored belt that was 17 @.@ 75 in ( 451 mm ) thick ; the citadel received the same thickness of steel . They had an armored deck that was 3 in ( 76 mm ) thick , and their conning tower was armored with 9 @.@ 8 in ( 249 mm ) of steel plate . The barbette had 14 @.@ 2 in ( 361 mm ) of steel armor . 
