On 3 May Dönitz sent Admiral Hans-Georg von Friedeburg, his successor as naval commander in chief, to the headquarters of British Field Marshal Bernard Montgomery at Lüneburg, with an offer to surrender the German forces in northwest Germany, together with the remaining elements of Army Group Vistula. Montgomery informed Admiral von Friedeburg that he could not accept the surrender of forces fighting on the Eastern Front, and that consequently Army Group Vistula would have to surrender to the Soviets, although British forces would accept the surrender of any German soldiers fleeing westwards. He proposed instead, following discussions between Eisenhower and the British government, that he would accept the surrender of all German military forces in Northwestern Germany, Schleswig-Holstein, the Netherlands and Denmark, including naval forces and warships in those areas. Friedeburg asked for 48 hours to consider this; Montgomery allowed him 24. The proposed inclusion of Denmark, and the German warships operating there, initially alarmed Dönitz, who wished at all costs to maintain Operation Hannibal, evacuating German troops across the Baltic to Danish ports; but on consideration, he reckoned he might secretly evade the obligation to surrender these ships if they were at sea on the date the surrender came into effect. Furthermore, as it was unlikely that Montgomery would promptly be able to deploy British forces to the Danish islands under German occupation, especially Bornholm in the central Baltic, there was every possibility that the evacuation proceeding there could continue in total disregard of the agreed surrender terms. Consequently, authorized by Dönitz, Friedeburg returned on 4 May and signed an instrument of surrender for all German troops and ships in the Netherlands, Denmark and Northwestern Germany. This was accepted by Montgomery on behalf of Eisenhower. This 4 May surrender would become effective at 8:00 am on 5 May; so Dönitz ordered all ships involved in Operation Hannibal to undertake a covert final evacuation voyage, while also unilaterally ordering all U-boat actions to cease. One crew in the evacuation fleet refused to set sail; so Dönitz ordered the ringleaders to be arrested for mutiny, tried by summary court martial, and shot.