Torpedoboot T21 was part of the 3rd TFlottila after commisioned and used in Norway until the end of 1943. From this time, the torpedo boat was used in the torpedo school in the Baltic Sea and was put into active service again at the end of 1944. Badly damaged handed over to the US after the war. Sunk by artillery fire of T19 with gas ammunition on board at Jutland on 10.06.1946.