As part of the 5th destroyer division, the Z20 Karl Galster was used to lay mine fields in the North Sea (Westwall) in September 1939, followed by four mine laying operation off the British coast until February 1940. Since the ship was in a shipyard during the invasion of Norway, it was the only surviving vessel of its class in April 1940 and took part in Operation Juno, together with the battlecruisers Scharnhorst and Gneisneau . Between July and September 1940 it was used of offensive mine laying in the southern North Sea and send to France until December 1940. After repairs the destroyer was attached to the 6th destroyer division operating in Norway until November 1941 when it returned to Kiel for major maintenance work. Back in Norway again, the ship run aground had to return to Germany again, and until Spring of 1943 the ship was often transferred between Norway and Germany. Stationed at the Alta Fjord, the ship participated in  Operation Sizilien in September 1943, followed by operations in Norway and Germany. In the final days of the war,  the destroyer was part of the evacuation fleet in East Prussia and decommissioned on 10.05.1945.

The ship was added to Soviet Fleet lists on 05.11.1945 and taken over by a Russian crew on 01.02.1946. After arrived at Libau on 13.02.1946 it was renamed to Prochny and served in the South Baltic fleet between 15.02.1946 and 24.12.1955. On 28.11.1954 it was renamed to PKZ-99 , two days later it was reclassified as floating barrack. The ship was removed from fleet lists on 25.06.1956 and scraped after that.