Attack on the hospital ship Guildford Castle

On 10 March 1918, at about half past five in the afternoon, a German submarine attacked the British hospital ship Guildford Castle in the Bristol Channel. The ship was bound for Avonmouth, the port of Bristol, and had 438 wounded soldiers on board. She was flying a large Red Cross flag and sailing with her navigation lights lit. The submarine fired two torpedoes. The first passed by; the second struck the port side abreast of the mainmast but did not explode. Guildford Castle reached port. No one was injured or killed.

Guildford Castle was a Union-Castle Line steamer of just under 8,000 gross register tons, built in 1911 by Barclay, Curle & Co. in Glasgow. She was a sister ship of the Gloucester Castle, which a year earlier had survived being torpedoed in the English Channel. From September 1914 she served as a hospital ship with 427 beds. She sailed first in South African waters, including during the campaign in German South West Africa in 1915, and then in the Mediterranean, among other times during the fighting for Gallipoli. In March 1918 she was commanded by Captain Thomas Martin Lang of the Royal Naval Reserve, who according to accounts saw both torpedoes.

The British chronicles of the war published in 1920–1922 recorded only that the ship had been torpedoed but reached port. More recent studies attribute the attack to U-55 under Kapitänleutnant Wilhelm Werner, the same man who on 4 January had sunk the Rewa. U-55 was then on patrol off the coast of Cornwall and in the Bristol Channel. That same day, about 15 nautical miles south-west of Trevose Head, she sank the Spanish steamer Cristina, bound from Port Talbot in Wales to Bilbao. Contemporary sources did not, however, name the attacker, so this attribution should be treated with some caution.

It was already the third attack on a hospital ship at the entrance to the Bristol Channel in little more than two months, after the sinking of the Rewa and, only two weeks earlier, of the Glenart Castle, on which 153 people died. The British official history of the naval war points out that in March 1918 the concentration of German submarines in the Irish Sea and the Bristol Channel did not slacken, and British countermeasures were having no effect. An attack on a clearly marked and lit ship full of wounded broke the Hague Convention, which protected hospital ships. This time hundreds of wounded survived only because the torpedo did not explode.