The class, sometimes referred to as the K class, was a class of light cruisers of the German and . The class comprised three ships named after German cities: , , and , all built between 1926 and 1930. These ships were the first of the with a modern cruiser design; their predecessor, , 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; was damaged by Norwegian coastal guns outside Bergen and sunk by British bombers the following day. was sunk by the British submarine ; only survived the attack on Norway.
After returning to Germany, 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.
Design
General characteristics
The ships of the 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 -class cruisers had a standard crew of 21 officers and 493 enlisted men. This later increased to 23 officers and 588–591 enlisted men, and during World War II, the crew size rose to between 820 and 850 officers and men. The ships carried a number of smaller vessels, including two picket boats, two barges, two launches, one cutter, and one dinghy. The ships were moderately good sea boats, but had the potential to capsize if internal stores were improperly loaded, and suffered from a slight lee helm. They heeled up to twenty degrees with the rudder hard over. They were nevertheless very maneuverable and lost little speed in a head sea. In a hard turn, they lost up to 20 percent speed.
In the 1930s, all three members of the class were modified to carry a pair of float planes for reconnaissance. They were equipped with an aircraft catapult to launch the planes and cranes to recover them after they landed in the water. The ships initially carried two Heinkel He 60 biplane float planes, replaced later in the decade with two Arado Ar 196 monoplane float planes. Only one aircraft could be stored on the catapult at a time; the second plane had to be disassembled and placed in storage, and the ships did not have a hangar to store it in.
Machinery
Their propulsion system consisted of four steam turbines and a pair of 10-cylinder four-stroke diesel engines. The turbines were split into three engine rooms, with the diesels in their own rooms directly aft of the turbines. Steam for the turbines was provided by six Marine-type double-ended oil-fired water-tube boilers. The engines powered a pair of three-bladed screws that were wide on the first two ships and in diameter on . The ships' propulsion system provided a top speed of and were rated at , though all three ships exceeded on speed trials. The ships carried of fuel oil as designed, but could store up to . This gave them a range of approximately at and at . Steering was controlled by a single rudder. The ships had three turbo-generators and two diesel generators for electricity; the generators had a combined output of at 220 Volts.