History of the B64/65 Project

These vessel were designed as a reply to the American Alaska Class large cruisers. Plans for these ships were drawn up, full scale tests were done to test the torpedo defense system in 1940, and the new 12.2" gun was developed and test fired by mid 1941.
By September 1940, the preliminary design was complete. The vessels would have looked much like a baby version of the Yamato Class battleships, with a similar profile. Speed was good and firepower was impressive, and the ship was capable of easily defeating any existing cruiser. The armor scheme was designed to make the ship immune from its own shell fire at ranges from 20,000 to 30,000 yards, and cruiser-caliber guns at most battle ranges. The main belt was inclined 20-degrees to increase its resistance to incoming fire, and the deck was designed to resist a 1000-pound bomb dropped from a dive bomber. The underwater defense system was designed to resist a 310-mm shell with an underwater trajectory or a 400-kilogram torpedo warhead. A dual purpose secondary was included, though the AA defense was very week and would have no doubt have been greatly increased.
With the war raging in China, and tensions rising with the USA, this design was put on the back burner while attention was given to projects that could reach fruition rapidly. Towards the end of 1941, when design specifications for the US Alaska Class became known, it was proposed to redesign the B65 to carry 14" guns in three twin turrets. Protection would have been increased to resist the larger weapon also, but the resultant decrease in speed and endurance was not acceptable. The project was cancelled.
It is probably just as well that these vessels were not built. Even without the war, these vessels would not have entered service until at least 1943. By then, the USA had built the Iowa Class battleships, designed to run down and destroy the Japanese Kongo Class battlecruisers. With speed equal to the B65, they carry 9 x 16" guns and an armor scheme designed to resist the same weapon. The Japanese design would not have been able to either out-gun or outrun the new American "battlecruiser killers".

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