On the night 9 May/10 May 1940, during the Battle of Norway, "Kelly" was torpedoed amidships by the German E-boat "S 31", under command of "Oberleutnant zur See" Hermann Opdenhoff (for which action Oblt.z.S. Opdenhoff was awarded the Knight's Cross). Severely damaged, she was taken under tow by the tug "Great Emperor" and for four days she was attacked by E-boats and bombers as she struggled back to port at three knots. The Navy Controller wrote that she survived "not only by the good seamanship of the officers and men but also on account of the excellent workmanship which ensured the watertightness of the other compartments. A single defective rivet might have finished her." She was repaired and returned to service.