Köln was a light cruiser, the third member of the Königsberg class that was operated between 1929 and March 1945, including service in World War II.

She was armed with a main battery of nine 15 cm SK C/25 (5.9-inch) guns in three triple turrets and had a top speed of 32 knots (59 km/h; 37 mph).

After the outbreak of World War II in September 1939, she conducted several operations in the North Sea, but did not encounter any British warships.

She remained on an even keel, with her gun turrets above water; this allowed her to provide gunfire support to defenders of the city until the end of the war in May 1945.

The tour lasted a full year; she stopped in ports across the globe, including in the Atlantic, Pacific, and Indian Oceans, and the Mediterranean Sea.

[8] In the final days of August 1939, Köln was stationed in the western Baltic to prevent Polish vessels from fleeing after the planned German invasion of Poland on 1 September; she was unsuccessful in this task.

The German force is found by British air reconnaissance on 8 April at the Norwegian south coast and promptly returns home, arriving on 10 October in Kiel.

[11][12] On 20–22 November, Köln and the cruiser Leipzig escorted the battleships Gneisenau and Scharnhorst on the first leg of their sortie into the North Atlantic.

On the 22nd, Köln and Leipzig were detached to join an unsuccessful patrol for Allied merchant ships in the Skagerrak along with Deutschland and three torpedo boats.

[13] On 13 December, Köln, Leipzig, and Nürnberg sortied into the North Sea under the command of vice-admiral Günther Lütjens in order to meet five destroyers returning from an minelaying operation off Newcastle and escort them home.

The force was attacked at 10h45 by the British submarine HMS Salmon which scored a hit on both Leipzig and Nürnberg, and then the roles were reversed when the five destroyers had to escort the cruisers back to Germany.

On 23 September she left Swinemunde together with the battleship Tirpitz, the cruisers Admiral Scheer and Nürnberg, three destroyers and five torpedo boats.

The next day, Köln provided gunfire support to ground troops attacking Soviet positions on Ristna.

[21] On 9 July 1942, Köln and the destroyer Z16 Friedrich Eckoldt departed Kiel to join the growing naval presence in Norway.

While en route, the flotilla was attacked by the British submarine HMS Tigris, but the torpedoes passed behind the German ships.

As a consequence permission was not given for the flotilla to proceed with the operation, instead PQ-18 was attacked by U-boats and bombers, which sank thirteen freighters.

As in the Arctic winter and darkness carrier escort was impossible, the Kriegsmarine was determined to attack the convoy in Operation Regenbogen, resulting in the Battle of the Barents Sea.

In the aftermath of that failed operation, a furious Hitler proclaimed that the Kriegsmarine's capital ships would be paid off and dismantled, and their guns used to reinforce the fortifications of the Atlantic Wall.

Admiral Karl Dönitz persuaded Hitler to retain a battle group consisting of the battleships Tirpitz and Scharnhorst, and the heavy cruiser Lützow.

[27] Köln left Altenfjord on 23 January 1943 in company with Admiral Hipper and the destroyer Z4 Richard Beitzen to return to Germany.

[18] On the night of 13–14 December,[30] Köln was attacked by British bombers in Oslofjord; several near misses caused damage to her propulsion system that required repair in Germany.

[18] On 30 March, B-24 Liberators from the Eighth Air Force attacked the harbor;[31] Köln was hit and sank on an even keel.