Azuma

Line drawings of proposed Japanese cruiser design B-65.

History

Design

The decisive victory over the Imperial Russian Navy at the Battle of Tsushima in the Russo-Japanese War of 1904-1905 was the catalyst of what became the Imperial Japanese Navy’s “Decisive Battle” doctrine. This strategy consisted of four primary components; a decisive surface fleet engagement with big guns, attrition tactics, quality over quantity, and nighttime torpedo attacks. When the Washington Naval Treaty was signed in 1922 limiting the size of Japan’s fleet to be greater than that of Italy and France, while lesser than that their more likely enemies of the United Kingdom and the United States, the emphasis of the Decisive Battle doctrine became all-encompassing in the Imperial Japanese Navy.

In 1936, the IJN formed the Night Battle Force. This force would attack the enemy’s outer defense ring of cruisers and destroyers at night to break through and launch torpedo attacks on the enemy’s battleships. What remained of the enemy fleet would be defeated by the IJN’s battle fleet the following day. To protect the Night Battle Force, a division of fast battleships or battlecruisers were assigned to the force. Initially the Kongo-class battlecruisers were chosen, and were modernized to fast battleships during the 1930s. The Japanese plans, however, intended to eventually replace the Kongo’s with four heavy and brand-new ‘super’ cruisers.

As originally envisioned in 1936, these ships — what would later become the B-64 and B-65 cruisers — would carry 12” guns, be protected by armor against 8” shells, and be capable of speeds up to 40 knots. These ships were designated as the “Super Type A” cruisers, and a total of six were planned to be ordered, two in the Circle Five Program production order set to begin in 1942, and the remaining four in the Circle Six Program production order that was abandoned in the early stages of planning due to the Japanese entry into World War II and shifting priorities. Ultimately, no ships of this type were ever ordered or laid down.

B-65’s hull was planned to be 240m long with a beam of 27.2m, with a designed draft of 8.8m. The planned maximum displacement was 34,800 metric tons. The planned machinery was to consist of eight Kampon boilers, which would produce steam for four turbines for a maximum output of 160,000 shp. This would allow B-65 to reach a maximum speed of 33 knots. With 4,545 tons of fuel oil on board the calculated cruising range was 8,000 nautical miles at 18 knots.

B-65’s main armament was planned with nine 310mm/50 guns, which were to be mounted in three triple turrets along the centerline, two forward, one aft. These guns were still undergoing development for the battlecruisers of both the B-64 and B-65 class, and could fire a 561kg heavy projectile at ranges up to 32.9km. Depending on the combat range the rate of fire could reach three rounds per minute and gun, while at higher elevations the reload times would be longer. The secondary armament was planned to consist of sixteen 100mm/65 guns, mounted in eight twin turrets with four on each side of the ship. Each gun was capable of firing a 13kg HE shell at sea targets 19.5km away, or at planes at an altitude of up to 13km. Unlike many other guns no other shells were provided. The rate of fire was usually around 15 rounds per minute and gun.

Anti-aircraft-armament did not differ from other ships, relying on four twin mounts with 25mm guns, and two 13.2mm twin machine guns. Unlike the heavy cruisers that preceded her, no torpedo armament was envisioned. A centerline mounted catapult would allow B-65 to carry up to three seaplanes.

B-65's armor was designed to be resilient against cruiser fire primarily, while also being strong enough to repel air attacks. The main belt was 190mm thick, and inclined at 20° to add further protection, which was supposed to protect against large caliber shells at ranges until 20km. The thickness was also used for the forward and rear bulkhead, while the deck armor and deck slopes were thinner at 125mm, which was deemed sufficient to resist an 800kg bomb and large caliber shells at ranges up to 30km. As protection against underwater explosions the torpedo defense system was designed to withstand an underwater explosion of 400kg.

Historical Inaccuracies

• Azuma is actually the name of an armored cruiser that was built in 1898 and fought in the Russo-Japanese War. No other ship in the Imperial Japanese Navy ever inherited the name.
• Azuma’s enhanced anti-aircraft suite in-game is envisioned in a late-war configuration that was not a part of her original design.

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  Artist's rendering of Design B-65.

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  Artist's rendering of Design B-65.