On the outbreak of war the Polish Navy despatched a number of ships to Britain with a a view to escorting convoys to Poland. With Poland swiftly overrun they operated alongside the Royal Navy. In May 1940 the Grom was assisting with operations to land troops and supplies at Narvik when she was bombed by German planes, one bomb hitting one of her loaded torpedoes causing an explosion that broke her in two. 59 men died.
Graphic footage of the action off Narvik and the rescue of men from the Grom: