The waterline main belt of "Asahi" consisted of Harvey armour high, of which was above the waterline at normal load, and had a maximum thickness of for the middle of the ship. It was only thick at the ends of the ship and was surmounted by a six-inch strake of armour that ran between the barbettes. The barbettes were thick, but only behind the upper armour strake. The barbette hoods were protected by 10 inches of armour on their face while their sides were 6 inches thick and the roof was thick. Diagonal bulkheads connecting the barbettes to the side armour were 12–14 inches thick, but only 6 inches thick at the lower deck level. The frontal armour of the casemates protecting the secondary armament was also 6 inches thick with the rear protected by armour plates. The flat portion of the deck armour was thick and thick where it sloped down to the sides of the ship. The conning tower was protected by 14 inches of armour.