It was backed by 75 millimeters of wood to make a better fit between the hull and the armor. The forward end of the citadel was protected by other armor and the transverse bulkhead was therefore only thick, barely enough to consider as splinter protection. However, the rear bulkhead had no other protection and was thick. These thin bulkheads left the end magazines very vulnerable to shells fired from bearings in front of or behind the ship. The upper belt was thick and had a height of . It thinned to 75 mm forward of the casemates all the way to the bow. The casemates were also protected by a transverse bulkhead from axial fire as well as a 25 mm screen between each casemate. Behind the side armor was an inboard longitudinal splinter bulkhead that was thick, but the casemates had their own separate 25 mm splinter bulkhead. The main gun turrets had sides thick with 125 mm roofs. 50 mm plates protected the gun ports and bulkheads separated each gun. The barbettes were 250 mm thick, but reduced to 125 mm below the upper deck, except in the forward and rear turrets which thinned only to . The forward conning tower sides were thick with a roof and 250 mm supporting tube which reduced to 100 mm below the upper deck. The rear conning tower also had 300 mm sides and a 250 mm support tube, but the roof was only 100 mm thick. The funnel uptakes were protected by 75 mm of armor above the upper deck, but this reduced to below it. The upper deck was thick while the middle deck was 25 mm thick over the armored citadel. Outside the citadel the middle deck was 37.5 mm thick and the lower deck was 25 mm thick. Underwater protection was minimal as there was only an unarmored watertight bulkhead behind the upwards extension of the double bottom. Construction All three ships were laid down on 30 October 1911, but this was just a ceremonial event as the design had not yet been finalized nor the contracts signed. A contract was finally signed on 13 April 1912 with Russud that specified delivery dates of 2 September 1915 for both Imperatritsa Mariya and Imperator Aleksander III. Imperatritsa Ekaterina Velikaya was built to a larger design that added over two million gold rubles to her cost and delayed the