The Gloucester Castle was a steam ship requisitioned by the British for use as a hospital ship during the First World War, operating in the Mediterranean between Lemnos and Malta and taking the wounded back across the English Channel from the Western Front. On one such voyage from Le Havre to Southampton on 31st March 1917 when carrying 399 patients including 300 cot cases, she was torpedoed by German U-boat U-32 off the Isle of Wight. All the patients were evacuated by the attendant destroyers and other transports, but three unfortunately died during the transfer. Although badly damaged she was eventually towed into port.
Not long after the resumption of the German announcement of unrestricted submarine warfare against shipping deemed to be supporting the Allied war effort, after landing 1,000 wounded at Avonmouth in the Bristol Channel, the Asturias was attacked by German submarine off the south Devon coast and struck by a torpedo which blew off her stern, killing 35 of her crew. The Captain of U20 which sank the Asturias was Capitanleutnant Walther Schweiger, who two years before had been in command of the U-Boat which sank the Lusitania. She was able to be beached near Bolt Head but her damage was so extensive that she was declared a total loss. However her hulk was put to use as a floating ammunition store at Plymouth for the rest of the war.
The German Army evacuates Serre, Miraumont, Petit Miraumont, Pys and (facing the I Anzac Corps) Warlencourt near Bapaume, falling back 25 miles to establish stronger positions along the Hindenburg Line. The shorter defensive position behind the Noyon Salient was built to economise on manpower, contain an Allied breakthrough and make possible a deliberate withdrawal to prepared positions utilising strong-points and protected by thick wire entanglements. By destroying the infrastructure and demolishing civilian buildings in the salient before a withdrawal, the Germans could dislocate Franco-British offensive preparations, by forcing them to advance into a wasteland. The British and French armies would need about eight weeks to rebuild roads, bridges and railways in the abandoned area before they could attack. A shorter Western Front could be held with fewer troops and by incorporating the lessons of defensive battle on the Somme, the importance of troop dispersal, reverse-slope positions, defence in depth and camouflage, German infantry casualties could be reduced. While the German army recuperated from the losses of 1916, protected by the Hindenburg Line and similar defensive positions on the rest of the Western Front, a return to unrestricted submarine warfare and a strategic bombing offensive against Britain were planned.
Wireless messages intercepted by the British Fifth Army from the rear of the three German divisions facing it ‘to dismantle and be prepared to move with all material, and not to leave anything behind’.
The German Government issued its warning to neutrals that from 1st February the waters around Great Britain, France and Italy were to be considered a barred zone, in which merchant vessels would be liable to be sunk without notice.