Battlecruiser Amagi (part 1, 1920/26-1930):
Under the Hachi-Hachi Kantai plan, the IJN order a class Battlecruisers was approved in late 1917: Four ships were to be built, named Amagi, Akagi, Takao and Atago.
The ships had a planned standard displacement of 41,217t and 47,000t at a full load. The class design was 250m long at the waterline, and 251,8 m overall. The ships would have had a beam of 30,8m and a draft of 9,5 m. The design staff intended to use turbine engines driving four propeller shafts, which were to be powered by 19 Kampon water-tube boilers, eleven of which were oil-fired, while the other eight were to have mixed oil and coal for fuel. This system was designed to provide 131.200 shaft horsepower for a top speed of 30 knots. The planned fuel stores amounted to 3.900 tons of oil and 2.500 tons of coal, giving the ships a maximum range of 8.000 nautical miles at the planned cruising speed of 14 knots.
The ships were to be equipped with a main battery of ten 409mm/45 guns in five twin turrets arranged along the centerline: two superfiring turrets fore, and three in line aft of the superstructure. The guns fired at a rate of fire between 1,5 to 2,5 rounds per minute and had a maximum elevation of 30 degrees, allowing a range of over 32.810 yards (30 km). Each gun had 90 rounds and an approximate barrel life of 250–300 shots.
The secondary battery was to have consisted of sixteen 140mm/50 guns mounted in casemates along the center of the ship. The guns had a maximum elevation of 25 degrees, which enabled a maximum range of 19.140 yards (17,50 km). Four 120mm/45 anti-aircraft guns were to have been mounted amidships, along with eight 24 in (610 mm) above-water torpedo tubes.
It was planned that the Amagi class would be protected by a main belt 254 mm thick, sloped at 12 degrees, and a torpedo bulkhead 73 mm thick. The main battery barbettes were designed to have between 229 and 280mm of armor plating, with turret faces beign 305mm thick, and the conning tower would have had armor ranging in thickness from 76 mm to a maximum of 356 mm. Deck armor was to have been 98 mm thick.
Akagi was the first ship of the class to be laid down; construction began on 6 December 1920 at the naval yard in Kure. Amagi followed ten days later at the Yokosuka naval yard. The projected completion dates for the first pair of ships were December and November 1923, respectively. Atago was laid down in Kobe at the Kawasaki shipyard on 22 November 1921, and was projected to be finished in December 1924. Takao, the fourth and final ship of the class, was laid down at the Mitsubishi shipyard in Nagasaki on 19 December 1921, and was also projected to be completed in December 1924.
The Washington Naval Treaty, signed in February 1922, greatly reduced the tonnage allowed for capital ships in the signatory nations. The treaty also instituted a moratorium on new warship construction, but allowed both Japan and Koko to complete one warship over 35.000tons each that was currently under construction. Having no warships under construction to fullfill the allowances, Koko was ultimately allowed the transfer of one of the Capital ships under construction in Japan. With the IJN immediately choosing to complete Tosa as a battleship, Koko would have been granted one out of Kaga, Akagi or Amagi, as Takao and Atago were deemed not enough advanced to justify their completion..
Just days after the WNT ratification, a meeting between IJN and KnK Naval Staffs was called in Tokyo to dcide the fate of the three ships. As the IJN, unlike Koko no Kaigun, was also allowed to complete two capital ships under construction as Aircraft Carriers it was at least certain that all three would have been eventually built. At first members of the various Staffs were prone to complete Amagi and Akagi as carriers and to transfer Kaga to Koko no Kaigun upon completion, but the consideration of having the USN and the RN completing three and two 30+knot battlecruisers each ultimately led to the decision of granting Amagi to Koko. In August 1922 the deal was officially made, with construction on the Battlecruiser immediately restarted at Yokosuka.
Amagi was launched in November 1922 at the presence of high officials from the IJN and KnK, the ship then starting her fitting out proceedings, with delivery to Koko no Kaigun planned for the first half of 1924.
On Saturday, September 1, 1923 the Great Kantō earthquake struck Tokyo area, seriously damaging Yokosuka Naval Arsenal facilities too. One of the dock cranes toppled over crashing onto Amagi's quarterdeck, but apart this the ship did not suffered any direct damage from the earthquake. Still works on the battlecruiser were halted while earthquake damage to the Naval Arsenal was repaired. Works resumed sporadically in december 1923, but they did not proceeded at full pace until 1925.
Amagi was finally declared complete on January 1st, 1926, immediately setting out for her sea trails, reaching 30,14 knots during her third run off Tateyama. Amagi then steamed for Koko, reaching Toumachi Bay in early April, where she was officially commissioned as Koko no Kaigun's Flagship on April 14th, 1926.
Manned by 1.562 officers and men the huge Battlecruiser became the most desired sea post for all cadets, and the focus of most recruiting campaigns, quickly gaining a sort of iconic aura even in the eyes of the civilian population. At the time of her commissionming Amagi outclassed by far every other Koko no Kaigun warships in nearly every field: she was nearly twice as big as the Yagumo class Battleships and five knots faster with just a slighly shorter operating endurance, her main guns could threw more weight and over 5.000yards farther than the Yagumos could do. Comparision with the Goryo Class Battlecruisrs was even more amiss.
During the first years of her career Amagi had the strange distinction of forming her own single-ship Sentai, the gap in speed with the two Yagumos beign considered excessive by the Naval Staff to field all three units under the same battlegroup. Amagi was finally joined -and also replaced as a Flagship- by the Battleship Kii in 1930 and by Battleship Owari in 1933, before endering the yards for her main refit in 1935.
Ships in class: (laid down-launched-commissioned - fate)
Amagi 1920-1922-1926 - ?