In April 1940, the German Navy was heavily involved in the invasion of Norway, where it suffered significant losses, which included the heavy cruiser sunk by artillery and torpedoes from Norwegian shore batteries at the Oscarsborg Fortress in the Oslofjord. Ten destroyers were lost in the Battles of Narvik (half of German destroyer strength at the time), and two light cruisers, the "Königsberg" which was bombed and sunk by Royal Navy aircraft in Bergen, and the "Karlsruhe" which was sunk off the coast of Kristiansand by a British submarine. The "Kriegsmarine" did in return sink some British warships during this campaign, including the aircraft carrier .