As long as the ships were not named, they were referred to by letters assigned in the chronological order of their planned construction.

[1] The M class was intended for use as a scout for the commerce raiding squadrons envisioned under German strategic thinking at the time, which would be formalized as the Plan Z construction program.

They were an improvement over previous designs like the Königsberg and Leipzig classes, which suffered from insufficient range to be effective commerce raiders.

In July 1937, the Oberbefehlshaber der Marine (commander in chief of the navy) requested proposals from both the naval design staff as well as private dockyards.

[3] During further development of the design, serious flaws became apparent, including the weakness of both the main battery and anti-aircraft armament, as well as the insufficiently thick armor protection.

The layout of the propulsion system was also problematic; both turbines were in the same engine room, and therefore each were vulnerable to disabling if the other was damaged.

They would have carried a pair of Arado Ar 196 seaplanes for reconnaissance, which would have been launched with a single steam catapult.

The propulsion system drove three screws, although four were considered for Q and R. The ships' electrical power was supplied by four generators that produced 2,400 kW at 220 volts.

The primary armament consisted of eight 15 cm L/55 quick-firing guns mounted in four twin turrets, in superfiring pairs fore and aft.

[3] The 15 cm twin turrets were Drh L. C/34 mounts—the same type as those fitted to the Bismarck- and Scharnhorst-class battleships, as well as a number of other designs.

The 15 cm guns had a rate of fire of between 6 and 8 45.3 kg (100 lb) rounds per minute, at a muzzle velocity of 875 meters per second (2,871 ft/s).

[7] The ships carried four 8.8 cm L/76 anti-aircraft guns in two twin turrets, aft of the main superstructure.

The inner layer of the armor belt was 50 mm thick in critical areas amidships, and tapered down to zero protection at the stern and bow.