Convoy ON 154

Convoy ON 154
Part of the Battle of the Atlantic
HMCS St. Laurent
Date 26–30 December 1942 Location North Atlantic Result German victory
Belligerents
Royal Canadian Navy Royal Navy United States Navy	Kriegsmarine
Commanders and leaders
Wion de Malpas Egerton † Guy Windeyer	Admiral Karl Dönitz
Strength
50 freighters 1 destroyer 5 corvettes 1 Special Service Vessel	20 submarines
Casualties and losses
13 freighters sunk (66,922 GRT) 177 killed 1 Special Service Vessel sunk 369 killed	1 submarine sunk 46 killed

Convoy ON 154 (ON(S) 154 or ONS 154) was a North Atlantic convoy of the ON convoys which ran during the battle of the Atlantic in the Second World War. It was the 154th of the numbered series of merchant ship convoys Outbound from the British Isles to North America. It came under attack in December 1942 and lost 13 of its 50 freighters; one U-boat was sunk.

Background

As western Atlantic coastal convoys brought an end to the second happy time, Admiral Karl Dönitz, the Befehlshaber der U-Boote (BdU) or commander in chief of U-boats, shifted focus to the mid-Atlantic to avoid aircraft patrols. Although convoy routing was less predictable in the mid-ocean, Dönitz anticipated that the increased numbers of U-boats being produced would be able to search for convoys. Only 20 per cent of the 180 trans-Atlantic convoys sailing from the end of July 1942 until the end of April 1943 lost ships to U-boat attack.

Bletchley Park

Main article: Ultra (cryptography)

The British Government Code and Cypher School (GC&CS) based at Bletchley Park housed a small industry of code-breakers and traffic analysts. By June 1941, the German Enigma machine Home Waters (Heimish) settings used by surface ships and U-boats could quickly be read. On 1 February 1942, the Enigma machines used in U-boats in the Atlantic and Mediterranean were changed to a four-rotor Enigma (Shark to the British). By mid-1941, British Y-stations were able to receive and read Luftwaffe W/T transmissions and give advance warning of Luftwaffe operations. In November 1942 the diversion of U-boats to North-West Africa against Operation Torch reduced losses on Atlantic convoys but world losses rose to 721,700 long tons (733,300 t) the worst month of the war. Only two U-boat s were sunk in November. In mid-December did GC&CS begin to break the four-rotor enigma messages. Having broken one Shark cypher in mid-December, the delay in breaking them was serious and on 25 December, no settings had been found for the last six days. From 25 December to 1 January 1943 traffic was read quickly.

B-Dienst

Main article: B-Dienst

The German Beobachtungsdienst (B-Dienst, Observation Service) of the Kriegsmarine Marinenachrichtendienst (MND, Naval Intelligence Service) had broken several Admiralty codes and cyphers by 1939, which were used to help Kriegsmarine ships elude British forces and provide opportunities for surprise attacks. From June to August 1940, six British submarines were sunk in the Skaggerak using information gleaned from British wireless signals. In 1941, B-Dienst read signals from the Commander in Chief Western Approaches informing convoys of areas patrolled by U-boats, enabling the submarines to move into "safe" zones. B-Dienst broke Naval Cypher No 3 in February 1942 and by March was reading up to 80 per cent of the traffic, which continued until 15 December 1942. By coincidence, the British lost access to the Shark cypher and had no information to send in Cypher No 3 which might compromise Ultra.

Prelude

Convoy formation, long rows, short columns

column 1	column 2	column 3	column 4
11 Ship	21 Ship	31 Ship	41 Ship
12 Ship	22 Ship	32 Ship	42 Ship
13 Ship	23 Ship	33 Ship	43 Ship

The ships departed Liverpool on 18 December 1942 and comprised 50 merchant ships, in ballast or carrying trade goods. The convoy commodore was Vice Admiral (Retd.) Wion de Malpas Egerton in Empire Shackleton. The convoy sailed in twelve columns of three or four ships each. The convoy formation was five miles (8 km) wide and 1.5 miles (2.4 km) long. ON 154 was a slow convoy, made up of ships that could manage 8 kn (15 km/h; 9.2 mph) at best. Slow convoys were particularly vulnerable, as their top speed was matched by the submerged speed of the U-boats and was just half their surface speed, thus making it easier for a wolfpack to form. The ocean escort for Convoy ON 154 was the Royal Canadian Navy (RCN) Mid-Ocean Escort Force Group C-1, led by  Lieutenant-Commander Guy Windeyer in the River-class destroyer HMCS St. Laurent. The group comprised the Flower-class corvettes HMCS Battleford, Chilliwack, Kenogami, Napanee, and Shediac.

C-1 was missing the Town-class destroyer HMS Burwell, which had mechanical defects and was not replaced. RCN ships generally suffered from overwork compared to their Royal Navy equivalents, and were more likely to be un-modernized. Convoy ON 154 included the convoy rescue ship Toward, the oiler Scottish Heather and the French-crewed 2,456 GRT special service vessel HMS Fidelity. Fidelity was armed with four 4-inch (102 mm) guns, four torpedo tubes and a defensive torpedo net. She carried the landing craft LCV-752 and LCV-754, two Kingfisher floatplanes and the Motor Torpedo Boat MTB 105. In the North Atlantic were the U-boat wolfpacks Ungestum with 13 boats and Spitz with 11 boats, on patrol in the Mid-Atlantic gap, where Allied air cover was unable to reach. A third pack, Falke acted as a reserve but attacked Convoy HX 219 instead.

Action

26/27 December

ON 154 was routed south towards the Azores to avoid storms and remained distant from escort support groups and out of range of Allied patrol bombers for longer than most convoys. U-662 reported the convoy on 26 December. That night U-356 torpedoed the leading ships from two of the starboard columns. Empire Union was hit at 01:40, Melrose Abbey was hit ten minutes later. Both British freighters sank at about 02:30. Toward rescued 63 survivors from the first ship and 47 from the second. In a second attack, U-356 torpedoed the Dutch freighter Soekaboemi at 04:10, and the British freighter King Edward at 04:15. King Edward sank within three minutes. U-356 was detected by the escorts and was sunk with no survivors following depth charge attacks by St. Laurent, Chilliwack, Battleford and Napanee. At dawn, Toward rescued 25 men from the King Edward and assisted Napanee, recovering all but one of Soekaboemi's crew. Soekaboemi remained afloat when abandoned at 07:30.

27/28 December

HMCS Chilliwack, photographed c. 1942

U-225 began stalking Scottish Heather as she refuelled some of the escorts 15 nmi (28 km; 17 mi) astern of the convoy on the afternoon of 27 December. U-225 was twice driven off by Chilliwack before hitting the oiler with a torpedo in a third approach at 20:40. The ship was temporarily abandoned but the second mate re-boarded her with ten men and sailed the ship out of the danger zone. At dawn he returned and pattern-searched for lifeboats. The oiler returned to England independently after recovering all of her crew.

28/29 December

U-260 began shadowing the convoy on the morning of 28 December and directed 18 U-boats to the convoy. Fidelity attempted to launch a Kingfisher but it capsized and sank at 19:15. While St. Laurent rescued the Kingfisher crew, a coordinated night attack began with U-boats entering the starboard side of the convoy at 19:58. U-591 torpedoed the Norwegian freighter Norse King at 20:00. U-225 torpedoed the British freighters Melmore Head at 20:03 and Ville de Rouen at 20:05. U-260 torpedoed the British freighter Empire Wagtail at 20:45. As Empire Wagtail disintegrated in an explosion that claimed all of her crew, Fidelity reported a main engine failure; Shediac was sent to assist her two miles (3.2 km) astern of the convoy.

Relief map of the North Atlantic Ocean

U-boats then entered the port side of the convoy. U-406 torpedoed the British freighters Lynton Grange at 21:20, Zarian at 21:23, and Baron Cochrane at 21:24. U-662 hit the damaged Ville de Rouen again at 22:10 and U-225 torpedoed the convoy commodore's freighter Empire Shackleton at 22:15 and the Belgian freighter President Francoui at 22:30. Disabled ships were also being attacked astern of the convoy. Baron Cochrane was sunk at 21:50 by U-123 and U-628 sank Lynton Grange a few minutes later. The crews had abandoned both ships when they were hit earlier. U-123 and U-435 sank Empire Shackleton at 22:55. U-591 sank the abandoned Zarian just before midnight.

Shediac was ordered to leave Fidelity 30 miles (48 km) astern and rejoin the convoy while searching for survivors. Shediac rescued 35 survivors from Melmore Head and 71 from Ville de Rouen between 03:10 and 03:30 and 24 from Empire Shackleton at 05:30. Shediac rejoined the convoy at 13:00 short of fuel and with inadequate provisions for the number of survivors aboard. Two lifeboats abandoned the damaged President Francoui, but the remainder of the crew attempted to sail independently to the Azores. U-225 torpedoed the ship again at 06:30 and it was sunk at 09:30 by U-336. The damaged Norse King was similarly attempting to reach the Azores when she was sunk by U-435 at 15:07. There were no survivors. The convoy escort was reinforced by the M-class destroyers HMS Milne and Meteor at 14:00 on 29 December after the arriving destroyers rescued 42 survivors from Baron Cochrane at 07:00, 52 survivors from Lynton Grange at 07:20 and 49 survivors from Zarian at 08:15.

HMS Fidelity 29/30 December

Photograph of a US Navy Vought OS2U Kingfisher on the water

Fidelity restarted main engines at 05:00 and declined the offer to dispatch a tug from Gibraltar. Speed was limited to two knots while streaming anti-torpedo nets when observed by Meteor and Milne at 05:30. U-615 found Fidelity while her main engines were again stopped for repairs between 10:15 and 11:00. U-615 identified Fidelity as a Q-ship and shadowed her cautiously. A reconnaissance flight by Fidelity's remaining Kingfisher observed two shadowing submarines and two of Empire Shackleton's lifeboats. Fidelity launched LCV-752 and LCV-754 to tow-in the lifeboats. Fidelity recovered the Kingfisher and the two landing craft with Empire Shackleton's survivors that afternoon and launched MTB-105 to conduct anti-submarine patrols through the night. U-615 launched four torpedoes at Fidelity at about 20:00, but the anti-torpedo net protected the ship from damage. MTB-105 experienced engine problems and lost contact with Fidelity at about 23:00. MTB-105 heard radio calls from Fidelity shortly after dawn, but had inadequate battery power to respond. U-435 torpedoed Fidelity at 16:30 and was surprised by the size of the resulting explosion and by the large number of men subsequently seen floating in the water where the ship had sunk. MTB-105 rigged a makeshift sail to try and reach land. Fidelity had on board 369 people (274 crew, 51 Marines and 44 survivors from Empire Shackleton), all were lost at sea, including Egerton, the convoy commodore.

30 December

HMCS Battleford, photographed on 5 October 1943 off the US east coast

On 30 December British destroyer HMS Fame arrived, Commander Ralph Heathcote, the commander of B-6 Escort Group taking over,

Windeyer, exhausted by the ordeal and now seeing torpedoes at every turn, was put to bed.

Battleford, Shediac, Milne and Meteor were released on 30 December to refuel in the Azores. leaving only four escorts remaining and as many as twelve U-boats in contact with the convoy. Following the loss of the convoy commodore, the two fast ships with large passenger complements (Calgary and Advastun), were invited to escape if they found an opportunity. HMCS St. Francis and the V-class destroyer HMS Viceroy reinforced the convoy escort before nightfall on 30 December. B-Dienst warned BdU of the reinforcement of the convoy escorts and the U-boats were ordered to disengage, many to rendezvous with U-117 to the west of the Azores.

Shediac and Meteor ran out of fuel before reaching the Azores. Battleford towed Shediac the last 40 nmi (74 km; 46 mi) and Meteor was towed the last 5 nmi (9.3 km; 5.8 mi). Once refuelled the four ships joined the search for survivors from Fidelity. Woodstock found and rescued the eight men aboard MTB-105, which included the two aircrew from the Kingfisher on 1 January; but, aside from the two-man Kingfisher crew rescued earlier by St. Laurent, there were no other survivors from Fidelity's crew of 325 and the men rescued from Empire Shackleton. Prescott also saved 26 crew from President Francoui whose Chief Officer, Lagay reported that the conduct of some of the survivors had been less than admirable, malingering, insubordination and violence being reported. Scottish Heather reached the Clyde on 2 January and the remainder of the convoy reached New York City on 12 January 1943.

Analysis

Map showing the location of the Azores

Convoy ON 154 lost 14 ships of 69,378 GRT and 486 men killed. It ranked as one of the worst North Atlantic convoy disasters of the war. The Admiralty was critical of the Canadians for the outcome of this voyage, comparing it unfavourably with the transit of ON 155 escorted by B-6 escort group without loss. However both Blair and Milner point out that the Admiralty also bore responsibility for routing the convoy so far south, through the widest part of the Air Gap, with a five day transit  without air cover. C-1 was also  expected to operate with a destroyer short, with inadequate provision for re-fueling and with without modern equipment, against a pack that outnumbered it by four to one. Milner also points out that B-6 had been given a more northerly course, and a faster convoy, and that the RCN groups had generally been assigned to the more vulnerable slow convoys of the SC and ON(S) series, while the RN groups had the faster HX and ON convoys.

Analysis of the convoy's losses also shows that of the fourteen ships sunk, nine were lost outside the convoy, having been damaged or disabled in a previous attack and forced to drop out. After the first attack by U-356 just five U-boats (U-225, U-406, U-591, U-260 and U-123) had succeeded in penetrating the escort screen, while the rest of the pack had been driven off, and had picked off the stragglers. Blair also points out that the German success against Convoy ON 154 was an exception; in December the Allies ran 16 trans-Atlantic convoys, containing some 650 ships; only three of them were attacked, and sank only 20 ships (i.e. apart from the fourteen in Convoy ON 154, only two from Convoy HX 217 and four from Convoy ON 153), plus seven other ships sailing independently.

Aftermath

Analysis

The attack on Convoy ON 154 was undoubtedly a success for the Germans, but the safe arrival of over two-thirds of the convoy's ships and the destruction of one of the attackers, whilst being outnumbered by nearly four to one, was not a complete failure by the escort forces. The Admiralty took the drastic decision to withdraw the RCN escort groups from the Atlantic, for intensive training at the RN facilities at Liverpool and Tobermory; refitting the Canadian escort ships with modern equipment, a tacit acceptance of the RCN's complaints. The burden of escorting slow convoys on the Atlantic route fell to the RN, leading to experiences not dissimilar to those suffered by the RCN.

Orders of battle

Convoy ON 154

Convoyed ships

Name	Year	Flag	GRT	Notes
Aldrastus	1923	United Kingdom	7,905
Algorab	1921	Netherlands	4,938	Destination Cape Town
Baron Cochrane	1927	United Kingdom	3,385	4,376 long tons (4,446 t) coal, sunk U-406, U-123 2 killed
Baron Elgin	1933	United Kingdom	3,942
Baron Inchcape	1917	United Kingdom	7,005
Belle Isle	1932	United States	1,960
Berkel	1930	Netherlands	2,130
Bonita	1918	Panama	4,929
Bornholm	1930	United Kingdom	3,177
Calgary	1921	United Kingdom	7,206
Dundrum Castle	1919	United Kingdom	5,259
E G Seubert	1918	United States	9,181
Empire Cougar	1919	United Kingdom	5,758
Empire Geraint	1942	United Kingdom	6,991
Empire Shackleton	1941	United Kingdom	7,068	Convoy Commodore W. de M. Egerton, 2,000 long tons (2,000 t) ammunition, aircraft, general cargo, sunk U-225, U-123, U-435 37 killed
Empire Simba	1919	United Kingdom	5,691
Empire Union	1921	United Kingdom	5,952	940 long tons (960 t) general cargo,sunk by U-356, 6 killed
Empire Wagtail	1919	United Kingdom	4,893	Sunk by U-260, all 43 crew killed
Esturia	1914	United Kingdom	6,968
Euthalia	1918	Greece	3,553
Fana	1939	Norway	1,375
Fort Lamy	1919	United Kingdom	5,242	Ship's Master, Vice-Convoy Commodore
Henry R Mallory	1916	United States	6,063
James Hawson	1930	Norway	6,074
Janeta	1929	United Kingdom	4,312
Jasper Park	1942	United Kingdom	7,129
King Edward	1919	United Kingdom	5,224	In ballast, sunk U-356, 23 killed
Kiruna	1921	Sweden	5,484
Lynton Grange	1937	United Kingdom	5,029	5,997 long tons (6,093 t) general cargo, sunk U-628, U-406
Melmore Head	1918	United Kingdom	5,273	In ballast, sunk U-225, 14 killed
Melrose Abbey II	1936	United Kingdom	2,473	3,403 long tons (3,458 t) coal, sunk by U-356, 7 killed
Norhauk	1919	Norway	6,086
Norse King	1920	Norway	5,701	5,453 long tons (5,541 t) coal, sunk U-435, U-591, 35 killed
Northmoor	1928	United Kingdom	4,392	Destination Cape Town, detached c. 25 December to Azores, arriving 30 December
Olney	1920	United States	7,294
President Francqui	1928	Belgium	4,919	In ballast, sunk U-225, U-336, 5 killed
Ramo	1921	Norway	2,334
Ravnefjell	1938	Norway	1,339
Runswick	1930	United Kingdom	3,970	Returned to England
Scottish Heather	1928	United Kingdom	7,087	Escort oiler, damaged U-225, returned to England
Soekaboemi	1923	Netherlands	7,051	5,000 long tons (5,100 t) general cargo, damaged U-356 sunk by U-441, 1 killed
Toward	1923	United Kingdom	1,571	convoy rescue ship
Tynemouth	1940	United Kingdom	3,168
Umgeni	1938	United Kingdom	8,149	Detached 1 January
Veni	1901	Norway	2,982
Vest	1920	Norway	5,074
Ville de Rouen	1919	United Kingdom	5,083	5,500 long tons (5,600 t) general cargo, sunk by U-591, U-662
Vistula	1920	United States	8,537
Wisla	1928	Poland	3,106
Zarian	1938	United Kingdom	4,871	7,500 long tons (7,600 t) general cargo, sunk U-406, U-591, 4 killed

Mid-ocean escort force

C1 Escort Group

Name	Flag	Type	Dates	Notes
HMCS Battleford	Royal Canadian Navy	Flower-class corvette	18–30 December 1942	Detached to fuel at Azores
HMS Burwell	Royal Navy	Clemson-class destroyer	—	Did not sail, engine trouble
HMCS Chilliwack	Royal Canadian Navy	Flower-class corvette	18– December 1942
HMS Fidelity	Royal Navy	Special service vessel	18– December 1942
HMCS Kenogami	Royal Canadian Navy	Flower-class corvette	18– December 1942
HMCS Napanee	Royal Navy	Flower-class corvette	18– December 1942
HMCS St. Laurent	Royal Canadian Navy	C-class destroyer	20– December 1942	Delayed sailing, defective HF/DF
HMCS Shediac	Royal Canadian Navy	Flower-class corvette	18–30 December 1942	Detached to fuel at Azores

Escort reinforcements

Escort reinforcements

Name	Flag	Type	Dates	Notes
HMCS Arrowhead	Royal Canadian Navy	Flower-class corvette	2–8 January 1943	Western Local Escort Force North
HMCS Chicoutimi	Royal Canadian Navy	Flower-class corvette	4–8 January 1943
HMCS Cobalt	Royal Canadian Navy	Flower-class corvette	7–12 January 1943
USS Cole	United States Navy	Wickes-class destroyer	1– January 1943
HMS Fame	Royal Navy	F-class destroyer	30– December	Cdr Ralph Heathcote Escort Group B6
HMS Mansfield	Royal Navy	Wickes-class destroyer	2– January 1943	West Support Force
HMS Meteor	Royal Navy	M-class destroyer	29–31 December	Detached to fuel at Ponta Delgada, Azores
HMS Milne	Royal Navy	M-class destroyer	29–31 December	Detached to fuel at Ponta Delgada, Azores
HMCS Nanaimo	Royal Canadian Navy	Flower-class corvette	7–12 January 1943	Western Local Escort Force South
HMCS Quesnel	Royal Canadian Navy	Flower-class corvette	7–12 January 1943
HMCS St. Francis	Royal Canadian Navy	Clemson-class destroyer	30– December
HMS Viceroy	Royal Navy	V-class destroyer	30– December

U-boats

Gruppe Spitz

Gruppe Spitz (data from Rohwer and Hümmelchen [2005] unless indicated)

Name	Captain	Flag	Class	Notes
U-260	Hubertus Purkhold	Kriegsmarine	Type VIIC submarine
U-662	Wolfgang Hermann	Kriegsmarine	Type VIIC submarine
U-123	Horst von Schroeter	Kriegsmarine	Type IXB submarine
U-659	Hans Stock	Kriegsmarine	Type VIIC submarine
U-225	Wolfgang Leimkühler	Kriegsmarine	Type VIIC submarine
U-406	Horst Dieterichs	Kriegsmarine	Type VIIC submarine
U-440	Hans Geissler	Kriegsmarine	Type VIIC submarine
U-203	Hermann Kottman	Kriegsmarine	Type VIIC submarine
U-664	Adolf Graef	Kriegsmarine	Type VIIC submarine
U-356	Günter Ruppelt	Kriegsmarine	Type VIIC submarine	Sunk 27 December

Gruppe Ungestüm

Gruppe Ungestüm

Name	Captain	Flag	Class	Notes
U-373	Paul-Karl Loeser	Kriegsmarine	Type VIIC submarine
U-435	Siegfried Strelow	Kriegsmarine	Type VIIC submarine
U-628	Heinz Hasenschar	Kriegsmarine	Type VIIC submarine
U-336	Hans Hunger	Kriegsmarine	Type VIIC submarine
U-591	HHans-Jürgen Zetzsche	Kriegsmarine	Type VIIC submarine
U-615	Ralph Kapitzky	Kriegsmarine	Type VIIC submarine
U-455	Hans-Martin Scheibe	Kriegsmarine	Type VIIC submarine
U-409	hans-Ferdinand Massmann	Kriegsmarine	Type VIIC submarine
U-441	Klaus Hartmann	Kriegsmarine	Type VIIC submarine

U-boat tanker

Name	Captain	Flag	Class	Notes
U-117	Hans-Werner Neumann	Kriegsmarine	Type IXB submarine	Minelayer in use as a tanker

See also

• Convoy Battles of World War II

Bibliography

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• Hinsley, F. H. (1994) [1993]. British Intelligence in the Second World War: Its Influence on Strategy and Operations. History of the Second World War, United Kingdom Military Series (2nd rev. abr. ed.). London: HMSO. ISBN 978-0-11-630961-7.
• Kahn, D. (1973) [1967]. The Codebreakers: The Story of Secret Writing (10th abr. Signet, Chicago ed.). New York: Macmillan. LCCN 63-16109. OCLC 78083316.
• Kindell, Don. "ON Convoy Series: Convoy ON.154". Convoy Web: Arnold Hague Convoy Database. Retrieved 17 September 2024.
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• Macksey, K. (2004) [2003]. The Searchers: Radio Intercept in two World Wars (Cassell Military Paperbacks ed.). London: Cassell. ISBN 978-0-304-36651-4.
• Milner, Marc (2018) [1985]. North Atlantic Run: The Royal Canadian Navy and the Battle for the Convoys. Toronto: University of Toronto Press. ISBN 978-1-4875-7728-5.
• Milner, Marc (2011) [2003]. Battle of the Atlantic. Stroud: Spellmount (History Press). ISBN 978-0-7524-6646-0.
• Mumford, J. Gordon (2009). "Battle of the Atlantic: Convoy ONS 154". Archive org. Retrieved 17 September 2024.
• Rohwer, Jürgen; Hümmelchen, Gerhard (2005) [1972]. Chronology of the War at Sea, 1939–1945: The Naval History of World War Two (3rd rev. ed.). London: Chatham. ISBN 978-1-86176-257-3.
• Ruegg, R.; Hague, A. (1993) [1992]. Convoys to Russia: Allied Convoys and Naval Surface Operations in Arctic Waters 1941–1945 (2nd rev. enl. ed.). Kendal: World Ship Society. ISBN 0-905617-66-5.
• Tarrant, V. E. (1989). The U-Boat Offensive 1914–1945. London: Arms and Armour. ISBN 1-85409-520-X.
• Woodman, Richard (2005) [2004]. The Real Cruel Sea: The Merchant Navy in the Battle of the Atlantic, 1939–1943 (Pbk. ed.). London: John Murray. ISBN 0-7195-6599-5.

Further reading

• Brown, David (1995) [1990]. Warship Losses of World War Two (2nd rev. ed.). London: Arms and Armour Press. ISBN 978-1-85409-278-6.
• Jordan, Roger W. (2006) [1999]. The World's Merchant Fleets 1939: The Particulars and Wartime Fates of 6,000 Ships (2nd ed.). London: Chatham/Lionel Leventhal. ISBN 978-1-86176-293-1.
• Morison, Samuel Eliot (1975). The Battle of the Atlantic 1939–1943. History of United States Naval Operations in World War II. Vol. I. Boston, MA: Little, Brown. OCLC 7395406.
• Rohwer, J.; Hummelchen, G. (1992). Chronology of the War at Sea 1939–1945. Naval Institute Press. ISBN 1-55750-105-X.
• Roskill, S. W. (1957) [1954]. Butler, J. R. M. (ed.). The War at Sea 1939–1945: The Defensive. History of the Second World War United Kingdom Military Series. Vol. I (4th impr. ed.). London: HMSO. OCLC 881709135. Retrieved 18 April 2018.
• Terraine, John (1999) [1989]. Business in Great Waters (Pbk. repr Wordsworth Editions, Ware ed.). London: Leo Cooper. ISBN 1-84022-201-8.
• Winton, John (1988). Ultra at Sea: How Breaking the Nazi code affected Allied Naval Strategy during World War II (e-book ed.). Leeds: Sapere Books. ISBN 978-1-80055-522-8.