IJN B-65 Nocturnal Battlecruiser

This model aboard the HIJMS Mikasa museum battleship in Yokosuka, Japan is of an Imperial Japanese Navy (IJN) World War II-era ship that was never built: the B-65-class "nocturnal battlecruiser."  These ships were proposed in 1939 as the core of a "Night Battle Force" of cruisers and destroyers that would sneak up on an enemy fleet, such as the U.S. Navy or Soviet Navy, and weaken it with gunfire and torpedoes overnight before it was sunk the next day in a hypothetical decisive battle for the Pacific Ocean.  The 35,000-ton B-65 battlecruisers would have been armed with nine 310mm cannons, dozens of smaller guns, and eight torpedo tubes, making them look like a smaller version of the Yamato-class battleships.  They would have also been capable of 38 miles per hour, which was extremely fast for a ship of that size.

The B-65 battlecruisers were redesigned in 1941 after the IJN learned about the capabilities of the U.S. Navy's new Alaska-class cruisers, which were authorized by the 1940 Two-Ocean Navy Act passed by Congress and signed into law by President Franklin D. Roosevelt.  The new specifications called for the main guns to be upgraded from 310mm to 356 mm and the armor to be thickened, which would have made the 40,000-ton ships a good deal slower than initially intended.  After losing four aircraft carriers to the Americans at the 1942 Battle of Midway, and finding the Pacific Islands about to be liberated by the U.S. Navy and Marines, the IJN postponed the B-65 battlecruisers indefinitely and decided to concentrate on aircraft carriers and auxiliary ships, abandoning the dedicated Night Battle Force altogether.