Uckermark

Germany's lack of overseas bases made supply ships and tankers essential for sustained naval operations in the Atlantic. The Kriegsmarine trained for underway replenishment during the 1930s and employed its supply network extensively during the Spanish Civil War. In spring 1939, warships and auxiliaries, including Gneisenau, conducted a major exercise in the central Atlantic that rehearsed procedures used during the first years of World War II.

The supply network reached its greatest operational importance during Operation Rheinübung in May 1941. After the loss of Bismarck, the Royal Navy located and captured or sank many of the German support ships deployed in the Atlantic.

Alongside converted civilian tankers, the Kriegsmarine ordered the purpose-built Dithmarschen class. Five of the nine planned ships entered service. Each could carry 7,933 tons of fuel, 972 tons of ammunition, 790 tons of provisions and 100 tons of spare parts. They also carried towing equipment for assisting damaged warships.

Plans to employ the ships as auxiliary cruisers were abandoned because combat would have exposed their vulnerable cargo and replenishment equipment. Two members of the class survived the war and continued in British and United States service into the 1950s.

Uckermark entered service as Altmark and supplied Admiral Graf Spee in the South Atlantic. Its return with more than 300 Allied prisoners led to the Altmark incident in Norway in February 1940, after which the damaged ship was repaired and renamed. Uckermark subsequently supported Scharnhorst and Gneisenau during Operation Berlin and sailed to Japan in 1942. An explosion during tank cleaning at Yokohama on 30 November killed 53 people and left the ship beyond repair.