Winston Churchill anxiously followed the victories and defeats of the U-Boats in the Atlantic. After the war had ended, he admitted that the U-Boat threat had been the one thing that truly scared him during the entire War. The pendulum miraculously swung with improved tactics and technology. In May 1943 out of a force of over 50 U-boats that challenged Convoy ONS5, eight were sunk and 18 were damaged, some seriously. Such losses were unsustainable and, with allied yards turning out ships at ever increasing rates, Donitz withdrew his wolf packs from the North Atlantic. Despite the terrible losses inflicted on the U-boat flotillas, young boys were still attracted to the submarines. As the U-boat memorial near Kiel records, by the end of the war, of the 39,000 men who went to sea in the U-boats, 27,491 died in action and a further 5,000 were made prisoners of war. Of the 863 U-boats that sailed on operational patrols, 754 were lost.