Ordered by Argentina from Blohm & Voss, Hamburg, the two ships were laid down in 1938 with completion slated for 1941. The ships were put on hold at wars start, but with Argentina's surrender to the Allies in early 1940, the Navy requisitioned the ships and ordered their completion. The design was for a fast cruiser that could also be used for minelaying. While the ship was fast, the high speeds were really only achievable in light/calm conditions, as the heavy superstructure forward tended to make the ship 'plunge'. Good armour was fitted, equivalent to most cruisers of its size. The Allies classed these ships as 'heavy' cruisers because of their 8.2" main guns, but with only six main guns the Germanic States Navy named these ships after towns as they considered them 'general' cruisers.
The two ships proved useful as destroyer leaders, and especially so when the destroyers were also carrying mines. They were considered a bit under armed for their size, but in their various battles and skirmishes proved they were useful additions to the fleet.