Early as spring of 1936, design studies for a new class of Light Cruisers started. All previous build CLs were not able to fulfill their planed task as commerce raiders because of their too short range, therefore the new CL called Kreuzer M
should get an enlarged endurance. Like the earlier CLs those ships should get a mixed propulsion system consisting of diesel engines for slower cruise speed and steam turbines for high speed. In relation to their size, those ships would have been not very heavily armed and protected, compared with Allied designs like the British Southampton
After the first four ships (M,N,O,P) an improved version (Q and R) should have been build. Besides an slightly increased size, the heavy antiaircraft armament should have been increased and the fire control of these guns should have been improved.
With a projected construction time of two and a half years, the orders for the first four ships were given on May 28th 1938 to the shipyards Deutsche Werke in Kiel, the Kriegsmarinewerft Wilhelmshaven and the Germaniawerft in Kiel. While first work started as early as November 1938, it was planed to lay down the keel for the first ship on November 1st 1939, but after the outbreak of the war, the used material was scrapped in the shipyard.
For more information, see Kreuzer M.