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; Königsberg was damaged by Norwegian coastal guns outside Bergen and sunk by British bombers the following day.