August 1941 the boat was transferred to the 5th Flotilla also in Kiel where she was used as a school boat until December 1942. In January 1943 UD-4 was transferred to Gotenhafen where she served as a school boat for 24th Flotilla and 27th Flotilla until January 1945. From January to March 1945 she was based in Hela and transferred to the 18th Flotilla where she served as a school boat.[1]