Convoy OB 318

By the spring of 1941 the battle of the Atlantic was starting to have an increase in German U-boat losses. This forced Vizeadmiral Karl Dönitz to change his strategy and he now moved his wolf packs further west, in order to catch the convoys without their anti-submarine escort. OB 318 was a west-bound convoy of 38 ships, either in ballast or carrying trade goods, and sailed from Liverpool on 2 May 1941 bound for ports in North America. The convoy commodore was R.Adm. WB MacKenzie in SS Colonial.[2] It was escorted by 7 EG, an escort group led by HMS Westcott (Cdr. Bockett-Pugh) and comprising ten warships; these were joined in mid-ocean by 3 EG, a force of eight warships led by HMS Bulldog (Cdr J Baker-Cresswell). Opposing them was a force of nineteen U-boats, though in the event only six were in a position to pose a threat.[3] One of those was U-110 under the command of Kapitänleutnant Fritz-Julius Lemp. Lemp notoriously had been in command of U-30 in 1939, which had controversially sunk the 13,581-ton passenger ship Athenia.[4]

OB 318 was sighted on 7 May 1941 by U-94, which reported its position and commenced shadowing while U-boat Command (BdU) alerted other U-boats in the area. There were six U-boats within striking distance, and these were ordered to close with U-94's position. Meanwhile, during 7 May the escort force was joined by five ships from Iceland and the destroyers of 3 EG, which were to take over escort duties from the Western Approaches to a dispersal point at 34 West, a location south of Greenland. Three ships and the destroyers of 7 EG left for Iceland during 7 May, leaving the escort force still at ten warships.[3]

U-boats sank five ships from convoy OB 318; and three, including the convoy commodore's ship Colonial, were sunk before arriving by U-boats patrolling near their destinations. Thirty-three ships arrived safely at their destinations over the next two weeks.

Baker-Cresswell took U-110 in tow, but she sank within hours due to the damage she had sustained. Lemp was lost with 14 members of his crew, but a war correspondent, 4 officers and 28 men were rescued and sent to Scapa Flow as prisoners of war. At Scapa Flow experts from Bletchley Park were waiting and were exceptionally surprised with what they collected and took back with them.[10] The capture of the Enigma machine was highly secret at the time, and none of the crew knew of the significance. The machine itself significantly assisted the work in hand at Bletchley Park in breaking German naval codes. This was the first fully functioning machine and the first one used to break the naval codes along with the capture of codes from a number of German weather ships during the same year.[11] Thanks to this Enigma machine, Bletchley were able to inform the Royal Navy and thus steered convoys away from where most groups of U-boat packs were present. The difference made was substantial; from when the information began to pour through in June 1941 Allied shipping losses were around 432,000 tons, but by August it had dropped to less than 80,000 tons.[12]

The most important find as well being the Reservehandverfahren cipher, which was first solved at Bletchley Park in June 1941 by means of documents captured from U-110 and then later on with the important capture of code books and other important documents from U-559 on 30 October 1942. Thereafter it was solved using cryptanalysis led by Alan Turing for over three years. Some 1,400 signals were read during that period.[11] Baker-Cresswell was awarded the DSO and promoted captain. King George VI told him the capture of the U-110 cipher material had been "the most important single event in the whole war at sea".[6]

The film U-571 was partially inspired by the capture of U-110. The film however caused irritation and anger in Britain whereby the film's plot was Americanised. The anger came to such a point that at Prime Minister's Questions, Tony Blair agreed with questioner Brian Jenkins MP that the film was "an affront" to British sailors.[20] In response to a letter from Paul Truswell, MP for the Pudsey constituency (which includes Horsforth, a town proud of its connection with HMS Aubrietia), U.S. president Bill Clinton wrote assuring that the film's plot was only a work of fiction.[21] Despite the criticisms however David Balme was interviewed by the director of the film, Jonathan Mostow in which he described the capture of U-110 and the capture itself was mentioned at the start of the end credits as recognition and response to the criticisms.

• Ultra
• Cryptanalysis of the Enigma
• Kurzsignale

• Balme, David. OPERATION PRIMROSE: The Story of the Capture of the Enigma Cypher Machine from U11O Military History Journal Vol 9 No 3 - June 1993- The South African Military History Society
• Blair, Clay Hitler's U-Boat War The Hunters 1939-1942 (1996) Random House ISBN 0-394-58839-8
• Hague, Arnold : The Allied Convoy System 1939–1945 (2000). ISBN (Canada) 1 55125 033 0 . ISBN (UK) 1 86176 147 3
• Kemp, Paul (1997). U-Boats Destroyed, German submarine losses in the World Wars. Arms and Armour. ISBN 1-85409-515-3.
• Lenton, H.T. & Colledge, J.J. British and Dominion Warships of World War II Doubleday and Company (1968)
• Niestle, Axel (1998). German U-Boat Losses During World War II. Greenhill. ISBN 1-85367-352-8.
• Roskill, Stephen. The Secret Capture: U-110 and the Enigma Story. Naval Institute Press, ISBN 978-1-59114-810-4
• Roskill, Stephen : The War at Sea 1939–1945 Vol I (1954). ISBN (none)
• Sebag-Montefiore, Hugh. Enigma: The Battle for the Code W&N; First Edition, 2000. ISBN 978-0-297-84251-4
• van der Vat, Dan : The Atlantic Campaign (1988). ISBN 0-340-37751-8

• OB 318 at convoyweb
• OB 318 at uboatnet