Even before the outbreak of WW2, the Naval High Command of the Kriegsmarine was concerned about the firepower of its most modern destroyer vessels. Fearing they may be outgunned by comparable vessels of other nations, a study was initiated in 1936 about the possible upgunning of the Type 1934 and 1936 class destroyers with 15cm main guns.
The study quickly revealed that, although this upgrade was theoretically feasible, in practice it resulted in severe stability issues on the affected vessels and actually hampered their abilities more than increasing them.
However, whilst the Type 1934 and 1936 class destroyers kept their original 12.8cm main guns as a result of the conducted study, the Naval High Command didn’t wish to abandon the idea completely and ordered for modifications to be made to the existing Type 1936 design in order to accomodate for the desired firepower upgrade.
This resulted in the creation of Type 1936A which was ordered into production in 1938 and consisted of a total of 8 ships. Although this class was designed to allow for the realization of the desired firepower upgrade, it still suffered from the same problems highlighted by the initial study and was known to have reliability issues with its steam turbines.
In 1940, the first of a total of 7 Type 1936 (Mob) destroyers were laid down. These were designed in an effort to address some of the known issues of the upgunned Type 1936 destroyers as well as to simplify their design in order to allow for shorter construction times.
Only a handful of the upgraded Type 1936A and 1936A (Mob) destroyers were lost in combat during WW2. In fact, more than half of the ships of these two classes survived the war and were used by several allied nations post-war, including the US, UK, USSR and France. The last remaining ships of this class were decommissioned from active service in the late 1950s.