Early in World War II, at the height of “The Phony War” on the Western Front between Great Britain and France, and Nazi Germany, the Battle of the Atlantic raged between German U-boats and pocket battleships and British and French shipping and escorts. In December 1939 the German pocket battleship Admiral Graf Spee sank several British merchantmen, rescued the survivors and transferred them to the German tanker Altmark for transport back to Germany.
During the long cruise to Germany, the Altmark violated Norwegian national waters to escape the pursuing British destroyer HMS Cossack. The Norwegian Navy interred the Altmark but refused to let the crew from the Cossack search it for the prisoners. First lord of the Admiralty Winston Churchill radioed the captain with some of the best common sense rules of engagement ever, to search it anyway.
“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” -Winston Churhill
The Norwegians backed off but the German crew of the Altmark prepared to repel boarders. The Cossack pulled along side and forcibly boarded and captured the Altmark killing eight Germans and wounding 15 others. It was the last naval action in history with the recorded use of the cutlass. The Cossack’s crew searched the ship, yelling “Anyone Englishmen here?” When the captured merchant seamen answered “yes”, the captain of the Cossack coolly replied, “Well, the Navy is here”.
The Altmark Incident convinced both the British and German governments that neither side would respect Norwegian neutrality. The British invaded Norway on 8 April to cut off Germany’s much needed supply Swedish iron ore and to open up a supply route to the Finns who were fighting Hitler’s ally, the Soviets. The Germans invaded Norway on 9 April to secure U boat bases on the North Atlantic.