Before the Kongō class battlecruiser design was created, similar type of British ship construction had been studied thoroughly (Thunderer, Neptune, Lion and Indefatigable). During a council held on April 13, 1910, an order for new class of ships was discussed, but a final decision was not made until May 23, 1910. In December 1910, during the Parliament meeting, the Japanese Prime Minister Saitō proposed construction of, as he described them in his speech, “huge armoured cruisers” based on the British “Invincible” class.
According to the Prime Minister, in the first phase, a decision was made to order one ship from Great Britain, with initial displacement of 18,500 T, armed with eight 30 cm guns. Another ship, and perhaps an additional one, were to be built in Japan on the basis of the first ship’s design. Generally speaking, the requirements for the ship were not elaborate. It was to be a construction with armour, power plant and armament superior to its British-built counterpart. The requirements for the ships are presented by scheme in Table 1.
Later, other designs were created. The one designated B.45 (type II) called for a ship with initial dimensions 655’ x 93’ x 28; displacement of 26 500 T1 and 65,000 SHP. Three variants for different length were developed. The first calculations were made for a ship 660’ long, with 86,400 SHP engines; the second concerned a ship 663’ long, with 64,500 SHP engines; the third were made for a ship 685’ long, with 66,000 SHP engines. The estimated maximum speed was 27 knots. It is worth noting that on the basis of that design, a final one, designated B.46, was created. Further units of that class – Hiei, Haruna or Kirishima – were similar, but since they were built in Japanese shipyards, there was little difference between their final characteristics and those of the Kongō prototype.
It is worth remembering that the Kongō class battlecruiser design was strictly connected with two people. One of them was their main creator, Commodore Motoki Kondo. His professional career began in March 31, 1883, when he graduated from the engineering department of the Tokyo University. Three years later, Kondo went to Great Britain where he began maritime studies. Shortly after graduation on June 30, 1890, he returned to Japan. In the rank of lieutenant (technical), he began work in the construction office of the Yokosuka Shipyard. The knowledge he had acquired abroad presented him with a chance to be an academic teacher in the Tokyo University. His further career developed according to his personal expectations. In 1897, Kondo was promoted to constructor lieutenant commander and a year later, constructor commander. In 1902, he was promoted to the rank of constructor captain and began work in the Imperial Japanese Navy Technical Department (Kaigun Kansei Honbu). Commissioning of a British “Dreadnought” gave him an opportunity to go to Great Britain and have a closer look at the new battleship. After returning to Japan, on August 9, 1907, he started work in the 3rd Division of the Navy Technical Department, where he worked on new designs of Imperial ships. One of his first ones was the B 46 battlecruiser. After its completion, Kondo was promoted to the rank of constructor general (Zosen Sokan) on December 10, 1910. The other person connected with the Kongō design was Sir George Thurston responsible for adaptation of Japanese design requirements.
The contract for building the first of the four planned ships, was signed in December 1910. Cost of a single vessel construction was in initially estimated at 27,580,000 yen. Construction of the third in the series – battlecruiser Haruna – was commenced on March 16, 1912, in the Kawasaki Shipyard. The commissioning ceremony took place on April 19, 1915. The ship was classified as Soko Junyōkan No 2.
The battlecruiser’s hull had six main decks, two of which were above the armoured citadel and the other four were between the double bottom and the top armoured deck covering the citadel. The hull was divided by a longitudinal bulkhead running along the ship’s plane of symmetry. Because of that, the entire engine room was divided into two parallel sections. Between the engine room side bulkhead and the ship’s side, there were two rows of watertight compartments. The smaller, outer ones were empty while the inner ones, between the former and the engine room bulkhead, were filled with coal along the entire length of the boiler room. Their additional task was to protect the boiler and engine rooms against torpedoes and mines. Along with other watertight compartments placed in different parts of the ship, they guaranteed reserve buoyancy and increased the ship’s reserve displacement. Twenty watertight compartments divided the hull abeam. The crew quarters, magazines and main artillery turrets were located in the bow section. The boiler room was behind them, amidship. Eight watertight compartments housed coal-fired boilers supplying steam to the turbines. The main specifications of Haruna after her commissioning is presented in Table 2.