Altmark Incident - 16th February 1940

On the 16th of February 1940, a boarding party from the British Royal Navy seized the German supply ship Altmark in the territorial waters of then-neutral Norway and freed several British POWs. This incident contributed to Nazi Germany's plan to invade Denmark and Norway.

The Altmark was a 14,367-ton German tanker converted into an auxiliary warship with a cruising speed of 25 knots and armed with three six-inch guns. In the fall of 1939, it operated as a supply ship for the pocket battleship Admiral Graf Spee in the South Atlantic and the Indian Ocean. In addition, the Altmark functioned as transport for the captured crews of British ships sunk by the Graf Spee. On 6 December 1939, the Altmark separated from the Graf Spee, which was scuttled on 17 December 1939 off the coast of Montevideo, Uruguay, in the wake of the Battle of the River Plate. The Altmark's commander, Captain Heinrich Dau, ordered it to set a course for home on 24 January 1940.

For three weeks, the Altmark, carrying almost 300 captured British soldiers, went undetected by the British until a reconnaissance plane caught sight of the vessel on 14 February 1940, heading south in Norwegian territorial waters. On 16 February, a British force comprising the light cruiser H.M.S. Arethusa and five destroyers led by H.M.S. Cossack, under the command of Captain Philip Vian, sighted the Altmark off the coast of Norway, under escort by two Norwegian patrol boats. An attempt by the British to board the Altmark failed because it refused to stop and, instead, took refuge in the Jøssingfjord.

The Cossack followed it and Vian demanded the release of the POWs, but the Norwegians responded they had boarded the Altmark earlier and had found no POWs. Vian returned to international waters and requested further instructions from his superiors in London. The First Lord of the Admiralty Winston Churchill ordered Vian to offer to escort the Altmark and the Norwegian patrol boats back to the port of Bergen and to search the German ship there. If this offer was refused, Vian should board the Altmark, anyway. Vian reentered Jøssingfjord, determined to accomplish his mission even against Norwegian resistance.

The Norwegians refused to cooperate but did not prevent the Cossack from putting alongside the Altmark. An assault party boarded the German vessel. In a short firefight, four Germans were killed and five wounded, and, most importantly for the British, 299 British sailors were freed. The next day, the Cossack returned to England.

The Norwegian government protested the violation of its territorial waters by British warships. The British countered the accusation, insisting that Norway had violated international law by allowing a German warship with POWs on board to pass through neutral waters. The Altmark incident also raised doubts in Nazi Germany about Norwegian neutrality. As a result, Adolf Hitler demanded an acceleration of preparations for the invasion of Norway.