The Japanese destroyer Akizuki

Visualization 3D Piotr Forkasiewicz

Origins of the design
Akizuki was the lead ship of her class of destroyers in the Japanese Imperial Navy considered by many to be among the best Japanese warships of that type in service during World War II. Those long-range vessels were fast, heavily armed and featured surprisingly good electronics (at least by Japanese standards of the time).

Add to that the exceptionally graceful lines and the result is one of the most capable large destroyers in service with the IJN.
The Japanese Imperial Navy had amassed a good deal of experience in the design and construction of destroyers. Huge amounts of money and labor invested in this class of warships were to offset the U.S. Navy’s advantage in that field. The Japanese destroyers designed and built immediately after World War I were already on par with their U.S. and British counterparts, but the real breakthrough was the Fubuki – a warship which set the standard for large destroyers mounting 127 mm guns and very capable torpedoes. The ships were equally good in support roles for larger IJN vessels and offensive operations (including night time attacks). It was the destroyers that were to tear at the core of the U.S. Navy and secure victory for the Imperial Fleet.

A view of Akizuki from the port side and from astern.  [Drawings by Mariusz Motyka]

The fast-paced progress of naval aviation quickly put an end to the old axiom that the greatest threat to a warship was another warship. It was now clear that even the largest surface vessels were vulnerable to airborne attacks and to ever expanding arsenal of air-launched torpedoes and bombs. In addition, the growing number of submarines meant that the underwater threat was just as formidable. This was the end of the era of battleships and large cruisers, which had to give way to aircraft carriers and submarines. Despite this, some of the Japanese admirals continued to firmly believe in the old ideas of big guns and heavy armor, but the changing face of naval warfare could hardly be ignored. It was time to provide the fleet with effective protection against airborne and underwater threats.
The best way to counter the airborne threat was to extend a protective umbrella of carrier-borne fighters over the fleet. However, the design and construction of carriers and naval fighters, not to mention crew training, was a costly and lengthy affair. Another option was to introduce a new class of warships bristling with AA guns and purpose-built for protection against airborne attacks. The Americans had already begun the construction of the Atlanta class anti-aircraft cruisers, while the Royal Navy commissioned the new Dido class warships. At that time the Japanese Navy cruisers were mounting universal 127 mm guns, but the weapons proved to be rather ineffective in the anti-aircraft role. There was also the issue of employing the cruisers as escort vessels for the aircraft carriers. It quickly became obvious that older generations of cruisers were ill-suited for air defense and performed poorly in joint operations with carrier battle groups in rough sea conditions. Additionally, the older cruisers often had problems keeping pace with the carriers. Steaming at full speed they used huge amounts of fuel, which in turn greatly reduced their effective operating range. There was therefore a clear need for a fast warship mounting effective AA guns and capable of operating with large carrier forces. The new vessel would also need to have a respectable range and anti-submarine warfare capability.
The initial plans called for the construction of a large number of light anti-aircraft destroyers. Those were quickly revised, however, since the massive project would be prohibitively expensive. Instead of an armada of light vessels the Japanese decided to focus on the design of a large destroyer carrying the newest 100 mm guns, but no torpedo launchers. This was a new trend in the Japanese ship-building philosophy, which until then had favored destroyers with heavy offensive armament. The new design concept was later changed to include a quadruple torpedo launcher and became to be known as the Type B destroyer.

A view from the right side showing the aft main gun turrets. The Akizuki class destroyers featured four main artillery turrets in superimposed arrangements placed in the forward and aft section of the ship.  [Drawings by Mariusz Motyka]

The preliminary design work began in 1938 and the budget for the construction of the first units was approved in 1939. The initial plans were indeed ambitious and called for the construction of no fewer than 55 destroyers of the new class. The plans were later scaled down and in the end only 12 Type B destroyers were built. Those became known as the Akizuki (“Autumn Moon”) class. The name may sound rather poetic, but one should not forget the unique nature of the Japanese warship naming convention. For instance, aircraft carriers were typically named after mythical flying creatures (e.g. Taiho – Great Phoenix), while the destroyers often featured names related to the natural phenomena, such as storms, winds, the Moon, waves, clouds or rain.
Basic characteristics of the Akizuki class destroyers
The Akizuki class destroyers were the largest vessels of that type in service with the Imperial Japanese Navy. Only a few contemporary French designs were bigger than those marvels of Japanese ship-building technology. The “Autumn Moon” measured 134 m in length and displaced 2 701 tons (by comparison, the large Kagero class destroyers were 118.5 m long and had a standard displacement of 2 490 tons). Thanks to her dimensions and carefully designed hydrodynamic shape the Akizuki had an excellent seakeeping performance, which in many cases made her superior to some of the older light cruisers of the Imperial Navy. Apart from her size, the characteristic features of the Akizuki included four main battery superimposed twin gun turrets.
The destroyer was powered by a pair of steam turbines developing 52 000 shp, identical to the units used on the Kegoro class vessels. The Akizuki had a top speed of 33 knots and a very respectable range of 8 300 nm at 18 knots. This made her an ideal choice for escort duties for large carrier battle groups.
A noteworthy feature of the Akizuki was her main battery. While older Imperial Navy destroyers mounted universal 127 mm guns, Akizuki received the newest Type 98 L/65 weapons. Those dual-purpose guns were much more technologically advanced, had better characteristics and were more reliable than the 127 mm weapons. At high angle of elevation the guns could fire a 13.2 kg projectile up to 14 500 m, while surface range was 19 500 m (in practice the effective AA and surface range was 11 000 m and 14 000 m, respectively). The guns could be elevated up to 90° and had a practical rate of fire of 14 – 15 rounds per minute (this largely depended on the proficiency level of the 11-man crew manning the turret). The gun was indeed a superb weapon and its only drawback was a relatively short barrel service life. The destroyer also carried 25 mm AA guns – four in the early service life and several dozens by the end of the war. The main battery guns as well as light AA weapons featured fire control systems that included range finders and gun directors. The “Autumn Moon” also carried a quadruple launcher loaded with the deadly 610 mm torpedoes plus four reloads. Anti-submarine weapons included two throwers for Type 95 depth charges. Initially the ship carried a supply of 54 depth charges, but it was later augmented to 72.

Inside Akizuki’s bridge – view from the left side.  [Drawings by Mariusz Motyka]

The Akizuki class destroyers featured fairly sophisticated electronics suites. In 1943 the ships received Type 21 radar sets, followed by Type 22 installed in 1944. The Akizuki was also equipped with the Type 13 air search radar. Unfortunately, the radar sets were inferior to their U.S. counterparts and could not be integrated with the ship’s fire control system, which greatly limited combat capability of the Imperial Navy vessels, including the Akizuki class destroyers. In addition to the radar sets the new destroyers were also most likely equipped with radar warning receivers. Type 92 hydrophones and Type 93 sonar were used in anti-submarine warfare operations.
The Akizuki’s complement was initially 263 officers and sailors, but later grew to 335 due to installation of additional AA guns and electronic equipment.
In summary, the Akizuki class destroyers were well designed and capable warships, custom tailored to their intended employment. Their weaknesses included inferior radar and rather poor ASW capabilities when compared to their U.S. Navy counterparts. In the anti-aircraft role the Akizuki could have performed much better had she been equipped with medium-caliber AA guns (similar to a 40 mm Bofors weapon). The 25 mm guns simply did not pack enough punch and could not be trained fast enough to track fast-flying U.S. Navy aircraft. The guns’ relatively small caliber meant that even a direct hit would not always bring down an enemy aircraft. Having said that, the Akizuki class destroyers still deserve their place among the best World War II warships of that type.


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 [Drawings by Mariusz Motyka]


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