Design B-65 cruiser

A line drawing of the proposed Design B-65.
Class overview
Name	Design B-65
Operators	Imperial Japanese Navy
Preceded by	Amagi-class battlecruiser
Planned	2
Cancelled	2
General characteristics
Type	Super Type A cruiser
Displacement	Standard: 31,905 t (31,401 long tons)[1] Full-load: 35,000 t (34,000 long tons)
Length	240 m (790 ft) length at the waterline[1] 246.2 m (808 ft) length overall[1]
Beam	27.2 m (89 ft)[1]
Draft	8.8 m (29 ft) (trial)[1]
Propulsion	Four sets of shaft horsepower); this would have been able to drive the ship at 33 kn (38 mph; 61 km/h)[2]
Endurance	8,000 mi (13,000 km) at 18 kn (21 mph; 33 km/h)[1]
Armament	9 × 310 mm (12.2 in)/50 caliber guns (3 × 3)[1] 16 × 100 mm (3.9 in)/65 caliber Type 98 dual-purpose guns (8 × 2)[1] 12 × 25 mm (1 in) anti-aircraft guns (6 × 2)[1] 4 × 13 mm (0.5 in) Hotchkiss machine guns (2 × 2)[1]
Armor	Belt: 190 mm (7.5 in) inclined 20 degrees Barbettes: 210 mm (8.3 in) to 190 mm (7.5 in) Conning tower sides: 180 mm (7.1 in) Conning tower roof: 125 mm (4.9 in) Deck: 125 mm (5 in)[3]

Design B-65 was a class of Super Type A cruisers^{[A 1]} planned by the Imperial Japanese Navy (IJN) before and during World War II. As envisioned by the IJN, the cruisers were to play a key role in the Night Battle Force portion of the "Decisive battle" strategy which Japan hoped, in the event of war, to employ against the United States Navy.

Begun in 1939, plans were far enough along that tests were conducted with the main armament and against the underwater protection. Even though the ships were approved for construction under a 1942 fleet replenishment program, the prioritizing of aircraft carriers and smaller ships due to the war, followed by Japan's defeat, killed any chance of the B-65's construction.

Mission and plan

The Japanese navy's experience in the

After the Washington Naval Treaty of 1922 and the London Naval Treaty of 1930, each of which placed restrictions on the size of the IJN's fleet in comparison with the fleets of the western powers, notably the United States, the decisive battle strategy received increased emphasis within the IJN. In 1936, the IJN formed the Night Battle Force (Yasen Butai). As designed, the night battle force was to attack the hypothetical enemy's, usually envisioned by the Japanese to be the US Pacific Fleet, outer defense ring of cruisers and destroyers at night. After cracking the outer defense ring, IJN cruisers and destroyers were to launch torpedo attacks on the enemy's battleships. What remained of the enemy fleet was then to be finished-off by the IJN's main battleship line the following day.^[5]

The IJN assigned one division of fast battleships or battlecruisers to give additional firepower to the nocturnal attacks. The Kongō-class battlecruiser were initially assigned to this role and were upgraded to fast battleships over a seven-year period from 1933 to 1940. The IJN planned to eventually replace the four Kongō battleships with four heavy, "super" cruisers. As envisioned by the IJN in 1936, these ships, the B-65 cruisers, would mount 310 mm (12.2 in) guns, carry armor designed to withstand hits from 203mm (8 in) shells, and be capable of speeds up to 40 knots. They would be designated as "super-A-class cruisers" to signify their greater status than the A-class ships (heavy cruisers).^[1][6][7]

The plan for the cruiser class was finalized as part of the IJN's Circle Five and Circle Six warship construction plans of 7 January 1941. The plan called for six B-65s to be built in two increments, with the first two to be constructed in Circle 5 with the remainder in Circle 6.^[8] By this time, Japanese intelligence had learned the specifications for the United States Navy's Alaska-class large cruisers,^[9] which had been authorized for creation by the passage of the Two-Ocean Navy Act and ordered on 5 September 1940.^[8][10] The Japanese believed that these ships would form part of the American battle fleet's screen in times of war. Thus, the B-65s were now intended to counter the threat posed by the Alaska-class cruisers.^[8][11]

Design

Design work on the B-65s began in 1939.^[12] Preliminary plans for the new class were finished by September 1940, and they were far enough along that tests of the lower protection—the armor intended to counter torpedoes and any shells that fell short but still hit the ship (albeit underwater)—and main armament were conducted from 1940 to 1941.^[1]

These plans called for ships that bore a striking resemblance to the

In an attempt to counter the Alaska-class cruisers' 305 mm (12.0 in) guns, a proposal to increase both the main battery to six 356 mm (14 in) and armor protection to resist against the same was put forth. However, the increase in displacement (to almost 40,000 long tons (45,000 short tons; 41,000 t)) and reduction in performance this entailed meant that nothing came of the proposed changes.^{[9][14][A 2]}

Final plans and cancellation

As war with the United States loomed in 1941, the navy found that it had a more pressing need for aircraft carriers and auxiliary vessels. This need, plus a desire to complete the ongoing Circle Three and Four construction programs, delayed initiation of the Circle Five plan.^[16]

Following the Japanese navy's defeat at the Battle of Midway in June 1942, the Circle Five plan was significantly revised and Circle Six was postponed indefinitely. The new plan still called for the construction of two ships of Design B-65, which were given the hull numbers 795 and 796 with projected commissioning dates of 1945 and 1946, respectively. As the war progressed, however, strategic requirements further delayed the plans for the two cruisers. In the end, the B-65s' plans were never finalized and no contracts for their construction were ever placed.^[17][18][19]

See also

• List of battlecruisers of Japan
• Deutschland-class cruiser - German counterpart
• Alaska-class cruiser - US counterpart

Notes

References

Bibliography