15th February 1940 The Altmark incident.

In February 1940, the German tanker Altmark was returning to Germany with 299 British merchant sailors on board, prisoners of war who had been picked up from ships sunk by the pocket battleshipAdmiral Graf Spee. On its way from the southern Atlantic to Germany,Altmark passed through Norwegian waters. On the insistence of British contacts who had been pursuing the vessel, it was investigated three times on 15 February by the Royal Norwegian Navy. First, the tanker was boarded by officers from the torpedo boat HNoMS Tryggoff Linesøy Island, then by officers from the torpedo boat HNoMSSnøgg in the Sognefjord, and finally personally by Admiral Carsten Tank-Nielsen and naval personnel from the destroyer HNoMS Garmin the Hjeltefjord. In each instance, the men who boarded the ship carried out cursory searches and took the Germans' word that the vessel was conducting purely commercial business. Following the third boarding, Altmark was escorted southwards by the torpedo boats HNoMS Skarv and HNoMS Kjell and the guard boat HNoMSFirern. The British prisoners held in the ship's hold reportedly made strenuous efforts to signal their presence, even though international law did not ban the transfer of prisoners of war through neutral waters. The Norwegian search parties however did not inspect the hold, and allowed the ship to continue on its way.

Altmark was then spotted off Egersund later the same day by British aircraft, which raised the alarm in the Royal Navy. The aircraft were stationed at RAF Thornaby, in the North East of England. After being intercepted by the destroyer HMS Cossack, captained by Philip Vian,Altmark sought refuge in the Jøssingfjord, but Cossack followed her in the next day. TheAltmark's Norwegian naval escorts blocked initial attempts to board the ship, and aimed their torpedo tubes at the Cossack. Captain Vian then asked the Admiralty for instructions, and received the following orders directly from the then First Lord of the Admiralty Winston Churchill:

Unless Norwegian torpedo-boat undertakes to convoy Altmark to Bergen with a joint Anglo-Norwegian guard on board, and a joint escort, you should board Altmark, liberate the prisoners, and take possession of the ship pending further instructions. If Norwegian torpedo-boat interferes, you should warn her to stand off. If she fires upon you, you should not reply unless attack is serious, in which case you should defend yourself, using no more force than is necessary, and ceasing fire when she desists.The British government made no particular objection to the fact of a prison ship traversing neutral waters. In fact in official papers regarding the incident they noted the fact that the Royal Navy had done the same, for example in December 1939 when the cruiserHMS Despatch passed through the Panama Canal, which was neutral waters, with German prisoners aboard from the freighter Düsseldorf. But the crew of the Altmark had gone hundreds of miles out of their way to make the long run through Norwegian waters to Germany, constituting a clear abuse of Norway's neutrality, and a breach of international law. Besides, the Norwegian government had not permitted the Germans to transport prisoners through Norwegian waters, nor had the crew been truthful regarding the nature of their cargo and voyage.

The Norwegian forces refused to take part in a joint escort reiterating that their earlier searches of Altmark had found nothing. Vian then stated that he intended to board Altmarkand invited the Norwegians to take part, but this was also refused. In the ensuing action,Altmark ran aground. The British then boarded her at 22:20 on 16 February, and — after some hand-to-hand fighting with bayonets and the last recorded Royal Naval action withcutlass — overwhelmed the ship's crew and then went down to the hold. One of the released prisoners stated that the first they knew of the operation was when they heard the shout "Any Englishmen here?" from the boarding party. When the prisoners shouted back "Yes! We are all British!", the response was "Well, the Navy's here!" which brought cheers.^[6]

Six German sailors were killed and eight wounded by the British,^{[citation needed][dubious – discuss]} seven of whom were shot while trying to flee over the ice. This was used unsuccessfully as a defence by the Germans in the Nuremberg trials, as the British Commander rather than being tried himself, was decorated for the action.

HMS Cossack left the Jøssingfjord just after midnight on 17 February. The Norwegian escorts protested, but did not intervene. The official explanation later given by the Norwegian government was that, according to international treaty, a neutral country was not obliged to resist a vastly superior force.