of the Anglo-German Naval Agreement of 1935, Tirpitz and her sister were nominally within the limit imposed by the Washington regime that governed battleship construction in the interwar period. The ships secretly exceeded the figure by a wide margin, though before either vessel was completed, the international treaty system had fallen apart following Japan's withdrawal in 1937, allowing signatories to invoke an "escalator clause" that permitted displacements as high as . Tirpitz displaced as built and fully loaded, with a length of , a beam of and a maximum draft of . Her standard crew numbered 103 officers and 1,962 enlisted men; during the war this was increased to 108 officers and 2,500 men. She was powered by three Brown, Boveri & Cie geared steam turbines, each driving a screw propeller, with steam provided by twelve oil-fired Wagner superheated water-tube boilers. Her propulsion system developed a total of and yielded a maximum speed of on speed trials. She was armed with eight 38 cm SK C/34 L/52 guns arranged in four twin gun turrets: two superfiring turrets forward—Anton and Bruno—and two aft—Caesar and Dora. Her secondary armament consisted of twelve 15 cm L/55 guns, sixteen 10.5 cm L/65 and sixteen L/83, and initially twelve C/30 anti-aircraft guns. The number of 2 cm guns was eventually increased to 58. After 1942, eight above-water torpedo tubes were installed in two quadruple mounts, one mount on each side of the ship. As built, Tirpitz was equipped with Model 23 search radars mounted on the forward, foretop, and rear rangefinders. These were later replaced with Model 27 and then Model 26 radars, which had a larger antenna array. A Model 30 radar, known as the Hohentwiel, was mounted in 1944 in her topmast, and a Model 213 Würzburg fire-control radar was added on her stern Flak rangefinders. The ship's main belt was thick and was covered by a pair of upper and main armoured decks that were and thick, respectively. The 38 cm turrets were protected by thick faces and thick sides. Service history Tirpitz was ordered as Ersatz Schleswig-Holstein as a replacement for the old pre-dreadnought , under the contract name "G". The Kriegsmarinewerft shipyard in Wilhelmshaven was awarded the contract, where the keel was laid on 20 October 1936. The hull was launched on 1 April 1939; during the elaborate ceremonies, the ship was christened by Ilse von Hassell, the daughter of