Since air is only 21% oxygen (and 78% nitrogen), pure oxygen provides nearly five times as much oxidizer in the same tank volume, thereby increasing torpedo range. These torpedoes used an otherwise normal wet-heater engine burning a fuel such as Kerosene. The IJN's torpedo research and development focused on using highly compressed oxygen instead of compressed air as the fuel oxidizer in the torpedo's propulsion system. Torpedoes were the only weapon that gave small warships, such as destroyers, the potential to cripple or sink battleships. The Japanese Navy invested heavily in developing a large, heavy, and long-range torpedo, the Type 93. After the number of American warships was sufficiently reduced, the IJN would commit its own presumably fresh and undamaged battleships to finish off the U.S. Navy's fleet in a succession of minor battles, mostly at night. Navy, it planned to use light forces ( light cruisers, destroyers, and submarines) to whittle down the U.S. Since the IJN had fewer battleships than the U.S.

Navy's doctrine, presuming an invasion by Japan of the Philippines (an American commonwealth at that time), called for the battle line to fight its way across the Pacific Ocean, relieve or recapture the Philippines, and destroy the Japanese fleet. At the time, the most powerful potential enemy of the Japanese Navy was the United States Navy's Pacific Fleet. The torpedo design was inspired by the British oxygen-enriched torpedoes used on the Nelson-class battleships. The Type 93's development (in parallel with a submarine-launched model, the Type 95) began in Japan in 1928, under the auspices of Rear Admiral Kaneji Kishimoto and Captain Toshihide Asakuma.

It was the most advanced naval torpedo in the world at the time.

'oxygen torpedo') is also used, in reference to its propulsion system. In Japanese references, the term Sanso gyorai ( 酸素魚雷, lit. Navy, who spent much of the war in the Pacific Theater. It is commonly referred to as the Long Lance by most modern English-language naval historians, a nickname given to it after the war by Samuel Eliot Morison, the chief historian of the U.S. The Type 93 ( 酸素魚雷, designated for Imperial Japanese calendar year 2593) was a 610 mm (24 in)-diameter torpedo of the Imperial Japanese Navy (IJN), launched from surface ships.

Childs submarine drawing with torpedoes