Submarine XXIII series belonged to a subclass of small German submarines and was intended for operations in the North and Baltic Seas. The first submarine of this type was a small submarine of the II series. As a result of the sharp strengthening of the anti-submarine forces of England from the end of 1940, military operations of the Kriegsmarine were transferred to the Atlantic, where medium and large submarines began to operate. The construction of small submarines of the II series and its modifications was stopped, preferring larger submarines. Again, the idea of ​ ​ fighting the enemy fleet in coastal British waters with the help of small submarines returned in 1943, but already at a fundamentally new technical base. Then mass production of new generation submarines of the XXIII series was launched.