Königsberg-class cruiser (1927)  The "Königsberg" class, sometimes referred to as the K class, was a class of light cruisers of the German Reichsmarine and Kriegsmarine. The class comprised three ships named after German cities: "Königsberg", "Karlsruhe", and "Köln", all built between 1926 and 1930. These ships were the first of the Reichsmarine with a modern cruiser design; their predecessor, "Emden", was based on World War I-era designs. They were armed with a main battery of nine guns and with twelve torpedo tubes. All three ships of the class were used extensively as training cruisers throughout the 1930s. They went on numerous overseas cruises and participated in the non-intervention patrols during the Spanish Civil War in 1936–1939. After the outbreak of World War II in September 1939, the three ships laid defensive minefields in the North Sea. They all saw action in Operation Weserübung, the invasion of Norway, in April 1940; "Königsberg" was damaged by Norwegian coastal guns outside Bergen and sunk by British bombers the following day. "Karlsruhe" was sunk by the British submarine ; only "Köln" survived the attack on Norway. After returning to Germany, "Köln" operated Flettner Fl 282 helicopters as an experiment. She provided gunfire support to German ground forces during Operation Barbarossa, the invasion of the Soviet Union in 1941, and returned to Norway in 1942. Ultimately, she was sunk in Wilhelmshaven in March 1945 by American bombers. Her guns were still above water, which allowed her to support the defending German army against British ground forces until the final days of the war. The ships of the "Königsberg" class were long at the waterline and long overall. They had a beam of and a maximum draft of . They had a design displacement of and a standard displacement, as defined by the Washington Naval Treaty, of . They displaced at full load. The ships' hulls were constructed from longitudinal steel frames and incorporated extensive welding to save weight; up to 85 percent of the hulls were welded rather than riveted. The hull was divided into nineteen watertight compartments and had a double bottom that extended for 72 percent of the length of the hull. The "Königsberg"-class cruisers had a standard crew of 21 officers and 493 enlisted men.