The Altmark incident joined audacity to a limited political objective

The patrol placed Arethusa, two I-class destroyers, and three Tribal-class destroyers under Vian, an unusual instance of a destroyer-flotilla captain commanding the supporting cruiser. The I-class ships supplied particularly heavy torpedo armament, while the Tribals supplied the guns for close fighting. Acting on Churchill's orders, Vian used a multilingual Royal Naval Volunteer Reserve officer to negotiate past the Norwegian escort. He entered the fjord and sent Cossack alongside despite the German ship's attempt to crush her. The boarding party freed the prisoners in one of the Royal Navy's last close offensive boardings of its kind. Leaving Altmark and her crew behind achieved the rescue while limiting the diplomatic cost to Norway.