The sides of the main gun turrets, barbettes, and main conning tower were protected by of armor, except for the turret and conning tower roofs which were thick. The thickness of the decks ranged from in two layers. The underwater protection system consisted of the extension of the double-bottom upwards to the lower edge of the waterline armor belt, with a thin plate acting as the outermost bulkhead. It was backed by a torpedo bulkhead that consisted of two plates. The total thickness of this system was only , which made it incapable of containing a torpedo warhead detonation or mine explosion without rupturing.