Altmark was a German oil tanker and supply vessel, one of five of a class built between 1937 and 1939. She is best known for her support of the German commerce raider, the "pocket battleship" and her subsequent involvement in the "Altmark Incident". In 1940 she was renamed the Uckermark and used as supply tanker for the battleships and during Operation Berlin before sailing to Japan on September 1942 as a blockade breaker. Footage of the Altmark appears briefly in the 1942 British wartime propaganda movie The Day Will Dawn. The Altmark Incident Altmark (Captain Heinrich Dau) was assigned to support Admiral Graf Spee during her raid in the South Atlantic between September and December 1939. Seamen rescued from the ships sunk by Admiral Graf Spee were transferred to Altmark. After Admiral Graf Spee was heavily damaged by British cruisers in Battle of the River Plate and subsequently scuttled by her crew, in the Río de la Plata in December 1939, Altmark attempted to return to Germany, steaming around the north of Great Britain and then within the Norwegian littoral. On 14 February 1940 Altmark, proceeding south within Norwegian territorial waters, was discovered by three British Lockheed Hudson Mk.II aircraft from RAF Thornaby and pursued by several British destroyers led by . Late on 16 February 1940 in Jøssingfjord she was fired upon while the Norwegian Navy stood by and took no action save for raising a protest flag. The German tanker then received a boarding party from HMS Cossack. During an attempted escape across the ice, seven of the Altmark crew were shot down. During the skirmish Altmark was run onto the rocks. It had been the British intention to tow the ship back to a Scottish port, but the damage to the tanker's stern frustrated this idea. An attack by one belligerent upon its enemy in neutral waters is a breach of neutrality, in this case a breach of Norwegian neutrality by Britain. Because Hitler feared Norway would be insufficiently resolute to protect the German iron-ore traffic that passed legitimately along the Norwegian littoral and earlier had decided on 14 December 1939 on the invasion of Norway after discussions with Admiral Erich Raeder and Vidkun Quisling, ordered intensified planning on 19 February 1940 for attacks on Norway and Denmark, which eventually took place on 9 April 1940 under the code name Operation Weserübung. The British justification for the