Convoy SC-107
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Convoy SC 107 was the 107th of the numbered series of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
Slow Convoys of merchant ships from Sydney, Cape Breton Island to
Liverpool Liverpool is a city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the 10th largest English district by population and its metropolitan area is the fifth largest in the United Kingdom, with a popul ...
. The ships departed
New York City New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...
on 24 October 1942 and were found and engaged by a wolfpack of
U-boat U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare role ...
s which sank fifteen ships.Hague 2000 p.135 It was the heaviest loss of ships from any trans-Atlantic convoy through the winter of 1942–43.Hague pp.132, 137–138, 161–162, 164, 181 The attack included one of the largest non-nuclear man-made explosions in history, when torpedoed ammunition ships SS ''Hobbema'' and SS ''Hatimura'' - both were sunk, one exploded, with the German submarine also being destroyed in the explosion.


Background

As western Atlantic coastal convoys brought an end to the "
Second Happy Time The "Second Happy Time" (; officially Operation Paukenschlag ("Operation Drumbeat"), and also known among German submarine commanders as the "American Shooting Season") was a phase in the Battle of the Atlantic during which Axis submarines att ...
", Admiral
Karl Dönitz Karl Dönitz (sometimes spelled Doenitz; ; 16 September 1891 24 December 1980) was a German admiral who briefly succeeded Adolf Hitler as head of state in May 1945, holding the position until the dissolution of the Flensburg Government follo ...
, 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 effectively search for convoys with the advantage of intelligence gained through ''
B-Dienst The ''B-Dienst'' (german: Beobachtungsdienst, observation service), also called x''B-Dienst'', X-''B-Dienst'' and χ''B-Dienst'', was a Department of the German Naval Intelligence Service (german: Marinenachrichtendienst, MND III) of the OKM, t ...
'' decryption of British Naval Cypher Number 3. However, only 20 percent 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.


Discovery

''B-Dienst'' decrypted message traffic detailing routing and composition of convoy SC 107, and fifteen U-boats of wolfpack ''Veilchen'' (violet) were deployed to intercept it. The convoy was found and reported by , patrolling the same general area as wolfpack ''Veilchen'', on 29 October as the
Western Local Escort Force Western Local Escort Force (WLEF) referred to the organization of anti-submarine escorts for World War II trade convoys from North American port cities to the Western Ocean Meeting Point (WOMP or WESTOMP) near Newfoundland where ships of the Mi ...
Rohwer & Hummelchen 1992 p.170 turned the convoy over to Escort Group C-4,Milner 1985 p.290 supported by the convoy rescue ship ''Stockport''. obtained a HF/DF bearing when ''U-522'' sent the first convoy contact report at 16:24, and the convoy made a course change after dark in the hope of evading the shadowing U-boat.Waters, pp.31–34 Soon after, a
No. 10 Squadron RCAF No. 400 Squadron RCAF, No. 10 (Army Cooperation) Squadron RCAF was formed on 5 October 1932 and renumbered as No. 110 Squadron on 15 November 1937, and then as No. 400 Squadron on 1 March 1941, as the first of the Article XV squadrons, manned and l ...
Digby bomber sunk , patrolling in the area of the convoy. As the boats of ''Veilchen'' were sailing towards their assembly point, wolfpack boat was sunk by a RCAF
Lockheed Hudson The Lockheed Hudson is a light bomber and coastal reconnaissance aircraft built by the American Lockheed Aircraft Corporation. It was initially put into service by the Royal Air Force shortly before the outbreak of the Second World War and prim ...
. Wolfpack boat found the convoy and released ''U-522'' to sail off for other prey.


First attack on 1/2 November

''Stockport'' and ''Restigouche'' located 25
HF/DF High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate over ...
transmissions from the eight U-boats in contact with the convoy on the afternoon of 1 November, but the single destroyer was unable to investigate all of them. At sunset HMS ''Celandine'' was sent to investigate the closest HF/DF fix eight miles off the port quarter; and ''Restigouche'' made a sweep astern. After sunset, a clearing sky revealed the flickering '' aurora borealis'' to port silhouetting the convoy and its three remaining escorts. As ''Restgouche'' engaged an ASDIC contact six miles behind the convoy with depth charges and star shells, nervous merchant sailors revealed the convoy location by firing snowflake pyrotechnic mortars.Waters, pp.38–55 While ''Restigouche'' pursued another U-boat, ''Kapitänleutnant''
Siegfried von Forstner Korvettenkapitän Siegfried Freiherr von Forstner (19 September 1910 – 13 October 1943) was a German U-boat commander during World War II. He was also a recipient of the Knight's Cross of the Iron Cross. He and his entire crew of were killed ...
's passed the destroyer at 22:40 while overtaking the silhouetted convoy from astern. When corvette had a
radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
malfunction, ''U-402'' went undetected as it penetrated the starboard side on the convoy screen about midnight to torpedo the British freighter ''Empire Sunrise''. ''Empire Sunrise'' fired two flares and most of the ships in convoy fired snowflake mortars. ''U-402'' dived to avoid the rapidly approaching ''Restigouche'' whose depth charges were comfortably distant. ''Restigouche'' narrowly avoided torpedoes launched a short time later by as the convoy changed course 40 degrees to port to confuse the U-boats. While ''Celandine'' dropped astern to screen ''Stockport'' rescuing survivors from ''Empire Sunrise'', ''U-402'' twice more penetrated the convoy screen where ''Celadine'' had been and torpedoed the Greek freighter ''Rinos'' and British freighters ''Dalcroy'', , and ''Empire Leopard''. ''U-402'' was lightly damaged by machine-gun fire from corvette and by a projectile from a merchant ship. ''Kapitänleutnant'' von Forstner would receive the
Knight's Cross of the Iron Cross The Knight's Cross of the Iron Cross (german: Ritterkreuz des Eisernen Kreuzes), or simply the Knight's Cross (), and its variants, were the highest awards in the military and paramilitary forces of Nazi Germany during World War II. The Knight' ...
for his work in ''U-402'' during this convoy and in
Convoy SC 118 Convoy SC 118 was the 118th of the numbered series of World War II slow convoys of merchant ships from Sydney, Cape Breton Island, to Liverpool. The ships departed New York City on 24 January 1943Hague 2000 p.135 and were met by Mid-Ocean Escor ...
on the next patrol. ''U-522'' torpedoed the Greek freighter ''Mount Pelion'' and British freighters ''Hartington'' and ''Maratima''. During the melee, merchant ships avoided two torpedoes launched by , three from , and four from ; while ''Arvida'' avoided damage from machine-gun fire by several merchant ships who thought she might be a U-boat.


2 November

Rain and misty weather caused the U-boats to lose contact after ''U-522'' torpedoed Greek freighter ''Parthenon'' in a daylight attack. Escort Group C-4 was reinforced by the V-class destroyer from convoy HX 213 before nine U-boats regained contact when visibility improved on 3 November.


Second attack on 3/4 November

''Celandine'', ''Amherst'' and ''Vanessa'' attacked the gathering U-boats unsuccessfully while the convoy reassembled after losing cohesion in the fog. One of the straggling merchant ships avoided two torpedoes launched by ''U-438''.Waters, pp.60–72 ''U-521'' torpedoed the American tanker ''Hahira'' shortly after dawn on 3 November. ''Stockport'' was carrying 350 survivors by the time she picked up those from ''Hahira''. Harbor tugs and had been attached to the convoy for passage to Iceland, and were detailed to act as rescue ships because ''Stockport'' was carrying three times her intended capacity. The little tugs were ordered to keep their running lights on in their assigned rescue positions astern of the convoy to minimize chances they might be mistaken for U-boats. torpedoed the convoy commodore's freighter ''Jeypore'' after sunset on 3 November; but snowflake illumination was minimal because most ships had exhausted their supply of pyrotechnics during the earlier attacks. Corvettes and made unsuccessful counterattacks before torpedoed the Dutch freighter SS ''Hobbema'' and British freighters ''Empire Lynx'' and ''Hatimura'' at 23:10. The entire convoy and nearby U-boats were shaken thirty minutes later by a heavy explosion believed to have been one of the largest prior to atomic bomb testing. The magnitude of the explosion temporarily stopped the engine of the rescue tug six miles astern of the convoy and caused several ships to believe they had been torpedoed. ''Titus'' was abandoned before the captain realized she was undamaged and returned with a skeleton crew including survivors from other ships. U-boats submerged at a depth of 200 feet reported being severely jolted, and ''U-132'' is believed to have been destroyed by the detonation. The cause of the explosion was undetermined, but assumed to have resulted from detonation of the ammunition cargo of either ''Hobbema'' or ''Hatimura'' while they were sinking. On 4 November, ''Arvida'' and ''Celandine'' were detached to
Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
with ''Stockport'' and the two tugs overcrowded with a total of 590 survivors. ''U-89'' torpedoed the British freighter ''Daleby'' shortly before the convoy escort was reinforced by the
United States Coast Guard The United States Coast Guard (USCG) is the maritime security, search and rescue, and law enforcement service branch of the United States Armed Forces and one of the country's eight uniformed services. The service is a maritime, military, mult ...
cutter and the s and from Iceland.
No. 120 Squadron RAF Number 120 Squadron or No. CXX Squadron is a squadron of the Royal Air Force which was established as a Royal Flying Corps unit late in World War I, disbanded a year after the end of the war, then re-established as a RAF Coastal Command squadro ...
B-24 Liberator The Consolidated B-24 Liberator is an American heavy bomber, designed by Consolidated Aircraft of San Diego, California. It was known within the company as the Model 32, and some initial production aircraft were laid down as export models des ...
s scrambled from Iceland drove off the remaining U-boats, and the convoy reached
Liverpool Liverpool is a city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the 10th largest English district by population and its metropolitan area is the fifth largest in the United Kingdom, with a popul ...
on 10 November.


Ships in convoy


German losses

RCAF bombers, patrolling the area of Convoy SC 107, sunk the free-patrolling on 30 October and wolfpack ''Veilchen'' member on 5 November. Wolfpack ''Veilchen'' boat sunk herself through the explosion caused by her torpedoing of ''Hobbema'' (or ''Hatimura'') on 4 November.


See also

* Convoy Battles of World War II *
Operation CHASE Operation CHASE (an acronym for "Cut Holes And Sink 'Em") was a United States Department of Defense program for the disposal of unwanted munitions at sea from May 1964 until the early 1970s.Kurak, Steve "Operation Chase" ''United States Naval Instit ...
for a description of experimental detonation of obsolete munition cargoes in sinking ships to simulate nuclear testing.


Notes


References

* * * * * {{cite book , last=Waters , first=John M., Jr. , title =Bloody Winter , publisher =D. Van Nostrand Company , date =1967 , location =Princeton NJ SC107 Naval battles of World War II involving Canada C