The Western Approaches Tactical Unit (WATU) was a unit of the
British Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...
created in January 1942 to develop and disseminate
new tactics to counter German submarine attacks on trans-Atlantic shipping convoys.
It was led by
Captain Gilbert Roberts and was principally staffed by officers and
rating
A rating is an evaluation or assessment of something, in terms of quality, quantity, or some combination of both.
Rating or ratings may also refer to:
Business and economics
* Credit rating, estimating the credit worthiness of an individual, c ...
s from the
Women's Royal Naval Service
The Women's Royal Naval Service (WRNS; popularly and officially known as the Wrens) was the women's branch of the United Kingdom's Royal Navy. First formed in 1917 for the First World War, it was disbanded in 1919, then revived in 1939 at the ...
(Wrens).
Their primary tool for studying
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 ...
attacks and developing countermeasures was
wargames
''WarGames'' is a 1983 American science fiction techno-thriller film written by Lawrence Lasker and Walter F. Parkes and directed by John Badham. The film, which stars Matthew Broderick, Dabney Coleman, John Wood, and Ally Sheedy, follows Dav ...
. After the U-boat threat to merchant shipping was defeated, WATU continued to develop anti-submarine tactics for later stages of the war, including
Operation Overlord
Operation Overlord was the codename for the Battle of Normandy, the Allies of World War II, Allied operation that launched the successful invasion of German-occupied Western Front (World War II), Western Europe during World War II. The operat ...
and the
Pacific War
The Pacific War, sometimes called the Asia–Pacific War, was the theater of World War II that was fought in Asia, the Pacific Ocean, the Indian Ocean, and Oceania. It was geographically the largest theater of the war, including the vast ...
. WATU trained naval officers in its tactics by hosting week-long training courses in which the students played wargames. WATU formally ceased operations at the end of July 1945.
Mission
During
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, German submarines (
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) sank merchant ships in the Atlantic Ocean so as to deny supplies to Germany's enemies in Europe. Britain reacted by organizing the merchant ships into convoys which were escorted by warships armed with
depth charge
A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive Shock factor, hydraulic shock. Most depth ...
s. This strategy proved effective at repelling
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. During the inter-war years, Germany secretly developed new submarine tactics to counter the convoy system. The products of this research were the "wolfpack" tactics, wherein submarines would attack convoys in groups, exploiting the weaknesses of the convoy system, and new advances in submarine technology. The British, by contrast, had neglected to study submarine tactics during the inter-war years. They entered
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 ...
assuming that the U-boats would operate much as they had during the previous war, unaware that the Germans would come at them with new tricks.
[
As soon as Britain declared war on Germany (3 Sept 1939), Germany sent its U-boats to attack transatlantic shipping. The U-boats had a devastating effect. In 1938, Britain had received 68 million tons of imports, but in 1941 the U-boats reduced this to 26 million. Britain was not a self-sufficient nation, and eventually its reserves of food would run out and it would be forced to capitulate to prevent a famine. In March 1941, Prime Minister ]Winston Churchill
Sir Winston Leonard Spencer Churchill (30 November 187424 January 1965) was a British statesman, soldier, and writer who served as Prime Minister of the United Kingdom twice, from 1940 to 1945 Winston Churchill in the Second World War, dur ...
declared that Britain was fighting "the Battle of the Atlantic", and made anti-submarine warfare a top priority.
The Royal Navy understood from intercepted radio transmissions that the U-boats were operating in coordinated groups but did not know the specifics of their tactics. On 1 January 1942, Admiral Cecil Usborne assigned Commander Gilbert Roberts to establish a wargaming unit at the Western Approaches Command
Commander-in-Chief, Western Approaches was the commander of a major operational command of the Royal Navy during World War II. The admiral commanding, and his forces, sometimes informally known as 'Western Approaches Command,' were responsibl ...
in 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 ...
, to analyze the submarine attacks and develop defensive tactics. Roberts had designed naval wargames during a two-year stint at the Portsmouth Tactical School, using them to develop new strategies and tactics. Additionally, Roberts was a gifted communicator who would be able to train commanders in the tactics he was to develop.
Roberts moved to Liverpool to set up his tactical unit on the top floor of the Western Approaches headquarters. This assignment officially began on 23 February 1942.[ Most of the staff at Western Approaches were women from the ]Women's Royal Naval Service
The Women's Royal Naval Service (WRNS; popularly and officially known as the Wrens) was the women's branch of the United Kingdom's Royal Navy. First formed in 1917 for the First World War, it was disbanded in 1919, then revived in 1939 at the ...
(colloquially referred to as "Wrens"), and likewise Roberts recruited most of his staff from the Wrens. At total of sixty-six Wrens served at WATU from 1942 to 1945.[ Parkin (2019). ''A Game of Birds and Wolves'', Postscript: "By 1945, a total of sixty-six Wrens had completed the course in order to become staff at WATU or its sister units."]
Roberts and his team reviewed battle reports from convoy escort commanders, recreated the battles in wargames in order to deduce how the U-boats were operating, and then devised tactics by which the escorts could defeat the U-boats. Their first product was a tactic codenamed ''Raspberry'' ( see below). As well as devising tactics, WATU also trained naval officers in their use by having them participate in wargames. The training course lasted six days, from Monday to Saturday, and was held every week from February 1942 to the last week of July 1945. Up to fifty officers at once took the course. WATU not only trained British officers, but also officers from other countries such as Canada, the United States, New Zealand, Norway, South Africa, Poland, and Free France
Free France (french: France Libre) was a political entity that claimed to be the legitimate government of France following the dissolution of the Third Republic. Led by French general , Free France was established as a government-in-exile ...
.
In May 1943, Admiral Karl Doenitz ordered the U-boats to withdraw from the Atlantic, allowing merchant convoys to pass unmolested.
By 1944, WATU's existence was public knowledge. A journalist visited WATU in January 1944 to observe a wargame and published a short article in ''The Daily Herald''. An exposé appeared in ''Illustrated'' magazine the following month.
WATU continued to develop anti-submarine tactics and train officers until the end of the war. It officially ceased operations at the end of July 1945. It had trained close to 5,000 officers over its lifetime.
Legacy
After WATU was closed, Admiral Horton sent the following signal to its former members: "On the closing down of WATU I wish to express my gratitude and high appreciation of the magnificent work of Captain Roberts and his staff, which contributed in no small measure to the final defeat of Germany." Admiral Noble sent Roberts a letter in which he wrote: "...you had a great deal to do in winning the war because if we hadn’t won the Battle of the Atlantic we should undoubtedly have lost the war!"
What makes WATU a noteworthy episode in the history of military wargaming
A wargame, generally, is a type of strategy game which realistically simulates warfare. A professional wargame, specifically, is a wargame that is used by military organizations to train officers in tactical and strategic decision-making, to test ...
is that it was an early instance where wargames were used to develop solutions on the fly to problems that were occurring in an ongoing war. Up to that point, most wargames were played during peacetime to prepare officers for potential wars, and the scenarios they explored either were hypothetical or happened many years ago. This was made possible by communications technologies that were not available to wargamers in earlier eras (radio and telephone).
The training course provided by WATU appears in the 1951 novel ''The Cruel Sea'' (referred to as the "Commanding Officers' Tactical Course"). The author, Nicholas Monsarrat
Lieutenant Commander Nicholas John Turney Monsarrat FRSL RNVR (22 March 19108 August 1979) was a British novelist known for his sea stories, particularly '' The Cruel Sea'' (1951) and ''Three Corvettes'' (1942–45), but perhaps known best in ...
, had attended WATU during his service in the war. The scene did not appear in the 1953 movie adaptation.
The role of WATU in the Battle of the North Atlantic is highlighted in the 2022 television series 'U-Boat Wargamers', and which also emphasises how the unit's Royal Navy Wrens significantly contributed to WATU's success.
Headquarters
Western Approaches Command
Commander-in-Chief, Western Approaches was the commander of a major operational command of the Royal Navy during World War II. The admiral commanding, and his forces, sometimes informally known as 'Western Approaches Command,' were responsibl ...
was an operational command of Britain's Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...
, tasked with safeguarding British shipping in the Western Approaches
The Western Approaches is an approximately rectangular area of the Atlantic Ocean lying immediately to the west of Ireland and parts of Great Britain. Its north and south boundaries are defined by the corresponding extremities of Britain. The c ...
(the seas to the west of Ireland and Britain). Initially headquartered in Plymouth
Plymouth () is a port city and unitary authority in South West England. It is located on the south coast of Devon, approximately south-west of Exeter and south-west of London. It is bordered by Cornwall to the west and south-west.
Plymouth ...
, on the southern coast of Britain, it was moved north 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 ...
in February 1941. After France had fallen to the Germans, North Atlantic shipping convoys had been diverted around the north of Ireland to evade the German navy. Relocating Western Approaches Command to Liverpool sped up communications. Its headquarters was Derby House, a building located behind Liverpool's town hall; today the headquarters is a museum. The top floor, comprising eight rooms, was allocated to WATU. Most of the staff at Western Approaches HQ were women from the Women's Royal Naval Service
The Women's Royal Naval Service (WRNS; popularly and officially known as the Wrens) was the women's branch of the United Kingdom's Royal Navy. First formed in 1917 for the First World War, it was disbanded in 1919, then revived in 1939 at the ...
. Colloquially, they were referred to as "Wrens". When Roberts arrived at Western Approaches in January 1942, its commander-in-chief was Admiral Percy Noble, who was replaced by Admiral Max Horton
Admiral Sir Max Kennedy Horton, (29 November 1883 – 30 July 1951) was a British submariner during the First World War and commander-in-chief of the Western Approaches in the later half of the Second World War, responsible for British particip ...
in November 1942.
Staff
A total of sixty-six women from the Women's Royal Naval Service
The Women's Royal Naval Service (WRNS; popularly and officially known as the Wrens) was the women's branch of the United Kingdom's Royal Navy. First formed in 1917 for the First World War, it was disbanded in 1919, then revived in 1939 at the ...
(Wrens) served at WATU from 1942 to 1945.[
* Captain Gilbert Roberts - Director of WATU. Once commanded a destroyer but contracted ]tuberculosis
Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...
in late 1938 and was barred from serving at sea.
*Mary Poole - WRNS officer. The first female officer to take the WATU course.
*Laura Janet Howes - WRNS officer. Born in Antigua
Antigua ( ), also known as Waladli or Wadadli by the native population, is an island in the Lesser Antilles. It is one of the Leeward Islands in the Caribbean region and the main island of the country of Antigua and Barbuda. Antigua and Bar ...
. Mathematical prodigy. Nicknamed "Bobby".
*Elizabeth Drake - WRNS officer. When WATU was established, she was already working at Derby House as a plotter.
*Nancy Wales - WRNS officer. Born in Kingston upon Hull
Kingston upon Hull, usually abbreviated to Hull, is a port city and unitary authority in the East Riding of Yorkshire, England.
It lies upon the River Hull at its confluence with the Humber Estuary, inland from the North Sea and south-east ...
, joined the Wren
Wrens are a family of brown passerine birds in the predominantly New World family Troglodytidae. The family includes 88 species divided into 19 genera. Only the Eurasian wren occurs in the Old World, where, in Anglophone regions, it is commonly ...
s in 1941. She was a passionate hockey player, and was selected for her understanding of team tactics.
*Jean Laidlaw - WRNS officer. Scottish. Former Sea Ranger and chartered accountant.
* Janet Okell - WRNS rating. She was only 19 years old when she joined WATU in January 1942. She served at WATU for the whole duration. Okell was initially trained as a plotter, but she was soon participating in wargames as a player, commanding 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 and escort ships alike.
*June Duncan - WRNS rating. One of WATU's longest serving members.
Overview of the wargames
Gilbert Roberts was first introduced to wargaming during a stint at the Portsmouth Tactical School from 1935 to 1937. Roberts took to wargaming with great enthusiasm, and developed his own rulesets. Roberts' wargames were based on the wargames developed by Fred T. Jane
John Fredrick Thomas Jane (6 August 1865 – 8 March 1916) was the founding editor of reference books on warships ('' All the World's Fighting Ships'') and aircraft ('' All the World's Airships'') and the namesake of what would become Jane's Inf ...
in 1898 (''Jane Naval Wargame'' and ''Fighting Ships''). Despite the strong effect that 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 had during World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, Roberts' wargames at Portsmouth did not simulate submarine warfare, nor attacks on merchant convoys. In fact, nobody in the Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...
studied submarine warfare through wargames until the establishment of WATU in 1942.[ Parkin (2019). ''A Game of Birds and Wolves'', chpt. 7: "Despite the fact that during the First World War the Germans had used submarines to great effect to disrupt the convoys bringing food and supplies to Great Britain, neither U-boats nor convoys featured in the wargames of 1935. ..‘Submarines were not mentioned,’ Roberts wrote of the games he was tasked with designing. ‘Nor were convoys and attacks on them. Nobody connected Hitler’s rise … to the possibility of another Battle of the Atlantic. Nor did I, to be absolutely fair.’"]
At WATU, the wargames were conducted in the largest room of the top floor of Western Approaches HQ. The floor was covered with brown linoleum and in the center was a painted grid. This grid was the game board, or "the tactical table" as the Royal Navy referred to it. The gridlines were spaced ten inches apart, representing one nautical mile
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute ( of a degree) of latitude. Today ...
. Around the grid were vertical screens of canvas that had peepholes cut into them. The players who controlled the escort ships had to stand behind the screens and could only view the game board through the peepholes. The players who controlled the U-boats did not stand behind the screens and had an unrestricted view of the game board. The ships and surfaced U-boats were represented on the game board by tiny wooden models. The U-boats' movement lines were drawn in green chalk, a color which contrasted poorly with the brown tint of the floor, such that when viewed from an angle, these lines were practically invisible, so the players behind the screens couldn't make them out. The escort ships' movement lines were drawn with white chalk, which could be clearly perceived by the players behind the screens.
The players were given two minutes per turn to make decisions and give orders. The players issued their orders for their imaginary ships on pieces of paper that they passed to the Wrens—this prevented their opponents on the other side of the room from overhearing. The Wrens would then get down on the floor and compute the outcomes of the players' orders, drawing the trajectories of the ships in chalk. Roberts provided the Wrens with the performance characteristics of all ships concerned: the range of the U-boat's torpedoes, the speed of the ships, their turn speed, the precise capabilities of the escorts' sonar
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...
(then known as ASDIC
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on or ...
), how engine noise might distort listening attempts, visibility at night, etc.
Tactics developed
Notes on WW2 submarine warfare
Submarines of this era were powered by diesel engines and batteries. They could only use their diesel engines when surfaced, as these needed to breathe air to work. When submerged, the submarine used lead-acid batteries. The batteries were less powerful than the engine, so the submarine was reduced to about half-speed: e.g. a Type VIIC U-boat could travel at on the surface but only underwater. The batteries could be exhausted after an hour or so of maximum speed underwater. When the batteries were exhausted, the 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 ...
would be forced to surface for air and recharge the batteries with the diesel engine.
The British were the first to equip their warships with sonar
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...
to hunt enemy submarines. They called this technology "ASDIC
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on or ...
"; the term "sonar" was later coined by the Americans (this article will use the term "sonar" as it is more widely known). This technology sent loud pings into the water and located a submerged submarine by the echoes. The U-boats could hear these pings, of course, so they would know they were being hunted. In practice, ASDIC had an average detection range of . ASDIC could be ineffective if there was too much ambient noise in the water. The maximum speed at which a ship could travel while using its ASDIC was about , beyond which the noise of its own propeller and engine would drown out the echoes. Both the U-boats and the warships also had hydrophone
A hydrophone ( grc, ὕδωρ + φωνή, , water + sound) is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates an electric potenti ...
s with which they could passively listen for sound in the water.
Merchant ships travelled in convoys, surrounded by a ring of escort warships. The convoy itself moved at a speed of 7 to 8 knots.
U-boats usually attacked at night. The cover of darkness allowed them to travel at surface depth with less risk of being spotted by look-outs. Escort ships were equipped with star shell
A shell, in a military context, is a projectile whose payload contains an explosive, incendiary, or other chemical filling. Originally it was called a bombshell, but "shell" has come to be unambiguous in a military context. Modern usage so ...
s, which when fired in the air would release a burning flare held aloft by a small parachute. This would illuminate the surface of the water, making it easy to spot a surfaced U-boat.
Warships used depth charge
A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive Shock factor, hydraulic shock. Most depth ...
s to sink submarines. These are bombs that were dropped into the water around the U-boat. The hydraulic shockwave produced by the explosion would seriously damage if not sink any submarine within 10 metres.
''Raspberry''
During World War I, the U-boats typically attacked convoys from outside the formation, striking ships at the perimeter. But reports from convoys in 1942 showed that U-boats were sinking ships at the center of the formation. Roberts surmised that the U-boats were somehow sneaking into the formation undetected before firing their torpedoes. Roberts and his team tested various ways by which a U-boat might sneak into a convoy, sink a ship, and escape undetected. Only one tactic worked on the game board: The U-boat snuck into the convoy from the rear, on the surface so that it could use its diesel engine to outpace the convoy. Since these attacks happened at night and the look-outs tended to focus on the front, the U-boat was not easily spotted, and once inside the convoy it was indistinguishable from the other ships on radar. The U-boat would then sink a merchant ship with a torpedo at close range, then submerge to make its escape.
Roberts and his team developed the ''Raspberry'' maneuver. Upon seeing a convoy vessel being torpedoed, any escort was to fire two white rockets or Roman candles, then say the word "raspberry" over the radio to commence the maneuver. Any forward escorts maintain course, firing star shells. The escorts to the rear and flanks of the convoy converge towards the convoy at a speed of 15 knots. One rear escort sweeps the stern of the convoy. The other escorts, upon nearing the edge of the convoy, turn around and sweep away from the convoy firing star shells for 10 to 12 minutes. Then they turn and sweep back to their starting position. While doing this, all the ships fire star shells outwards to light up the surface of the water.
''Raspberry'' is likely a development of an earlier maneuver known as ''Buttercup'', which was developed by Frederic J. Walker, an escort commander. ''Buttercup'' was criticized by the Admiralty for not having all the escorts sweep for the U-boat in all directions. In ''Buttercup'', the escorts would only sweep to the side of the convoy where the attack was thought to have come from, which meant the U-boat could escape if the escort commander made the wrong call. Additionally, only the escort commander could order the maneuver, which could have caused a fatal delay. By contrast, ''Raspberry'' has all the escorts sweep the entire perimeter, and any of the escorts could order the maneuver.
It was Jean Laidlaw who proposed the name ''Raspberry'', as in "blowing a raspberry
Blowing a raspberry, strawberry, razzing or making a Bronx cheer, is to make a noise similar to flatulence that may signify derision, real or feigned. It is also used in childhood phonemic play. It is made by placing the tongue between the lips, ...
at Hitler".
''Raspberry'' was cancelled in May 1943.
''Pineapple''
''Pineapple'' was designed to be an alternative to ''Raspberry'' and ''Banana''. It was to be used when more than one U-boat was attacking the convoy, and was designed to do four things: (1) Force a second U-boat to dive before being able to attack; (2) Give a chance of detecting a U-boat which has already fired torpedoes; (3) Prevent another U-boat from sighting the convoy in any illumination used to detect the U-boat which has already attacked; and (4) Increase chance of detection of any submerged U-boat which is about to attack and to form a greater physical obstruction in the submarine attacking area.
Upon noticing a ship getting torpedoed, any escort fires two white rockets and then says the word "pineapple" over the radio to commence the maneuver. Depth charges are to be set to ten-charge shallow pattern. The escorts keep moving forward in zigzag patterns that are 2 miles wide, searching for the U-boats using sonar, radar, and star shells. The escorts facing the expected direction of the second U-boat fire star shells away from the convoy to search for the second U-boat. They were not to fire star shells into the convoy, and the escorts on the opposite side of the convoy were not to fire star shells at all — this was probably to avoid lighting up the convoy, which would have made it easy for the second U-boat to spot.
''Banana''
''Banana'' was intended for when a single U-boat attacked the convoy (unlike ''Pineapple'' which was intended for pack attacks). Along with ''Pineapple'', it supplanted ''Raspberry''.
Upon seeing a merchant ship being torpedoed, the escort was to fire two white rockets or Roman candles and signal "banana" over the radio, then begin sweeping with sonar and radar at maximum viable speed. The rear escorts fire star shells outwards, then move into the convoy to sweep with sonar in a zigzag pattern. The first of these escorts to reach the wreck of the torpedoed vessel carries out Operation ''Observant'' in the area. The escorts to the flanks of the convoy sweep towards the rear of the convoy until they were abreast of the rear escorts, after which they turn around and sweep forward in a zigzag pattern. The forward escorts were to sweep forward in a zigzag pattern.
''Beta Search''
''Beta Search'' was a maneuver by which an escort might be able to locate a U-Boat that it had spotted shadowing a convoy. The manual for escort commanders (''Atlantic Convoy Instructions'') noted that a single escort had a poor chance of finding and destroying a U-boat, but by assuming the most likely course the U-Boat would take and searching within that vicinity, the odds of success could be raised somewhat. ''Beta Search'' was a development of an earlier maneuver developed by Commander Frederic Walker called ''Alpha Search''. The advantage of ''Beta Search'' over ''Alpha Search'' is that ''Beta Search'' persuades the U-boat to move in a specific direction. The disadvantage of ''Beta Search'' is that the escort must be fitted with "special plotting equipment" to use it.
In ''Alpha Search'', the escort turns to head straight for the U-boat, which will prompt the U-boat to dive. The escort then turns 20 degrees. When the escort reaches the U-boat's "furthest towards" circle, it alters course towards the position the U-boat dived, moving in a zigzag with short legs pattern. Upon passing the location where the U-boat dived, the escort drops a marker in the water, then proceeds for the same distanced zigzagging. Then it turns 90 degrees towards the convoy and begins a search pattern known as Operation ''Observant''.
In ''Beta Search'', the escort turns towards the U-boat, but not directly towards it. The U-boat would likely react by submerging and following a course parallel to the convoy. The escort then moves towards the U-boat's predicted position along that course (this would be on a roughly 15 degree angle from the bearing on which the U-boat was spotted). When the escort reaches the U-boat's "furthest towards" circle, it starts "zigzagging with short legs". When the escort passes over the U-boat's predicted line of escape, it was to drop a sea marker in the water. When the escort reached the U-boat's "furthest away" circle, it was to turn 90 degrees towards the position where the U-boat dived and begin Operation ''Observant''.
''Step Aside''
''Step Aside'' was a maneuver by which a warship could attack a U-boat armed with acoustic torpedo
An acoustic torpedo is a torpedo that aims itself by listening for characteristic sounds of its target or by searching for it using sonar (acoustic homing). Acoustic torpedoes are usually designed for medium-range use, and often fired from a subm ...
es, specifically the T5 ''Zaunkönig'' torpedo, which the Royal Navy referred to as the GNAT (German Navy Acoustic Torpedo). This torpedo used built-in hydrophone
A hydrophone ( grc, ὕδωρ + φωνή, , water + sound) is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates an electric potenti ...
s to guide itself to its target by sound. The first use of this torpedo was on 20 September 1943 against convoy ON 202. The Royal Navy was already aware that the Germans had developed an acoustic torpedo through interrogations of captured Germans and decrypted communications. In the attack on ON 202, a frigate was hit in the rear while it was bearing down on the U-boat, something which could only have been done by a homing torpedo; the torpedo was drawn to the sound of the frigate's propeller. Roberts and his team at WATU developed a maneuver known as ''Step Aside'', in which the warship made sharp turns to dodge the acoustic torpedoes the U-boat might fire as the warship maneuvered into attack range. ''Step Aside'' was communicated by radio to escort commanders at sea on 23 September 1943.
''Step Aside'' was intended for warships that could not go faster than and which were not equipped with Foxer
Foxer was the code name for a British built acoustic decoy used to confuse German acoustic homing torpedoes like the G7 torpedo during the Second World War. A US version codenamed FXR was deployed at the end of September 1943 on all transatlanti ...
decoys.[''Conduct of anti-U-boat operations'', part 2, Chapter IV, paragraph 381]
(UK National Archives reference ADM 239/298) Most convoy escorts were frigates and corvettes, with a maximum speed of 16 to 20 knots. 24 knots was the speed at which the T5 torpedo moved, so ships which could go faster than that (destroyers) could just outrun the torpedo.
Upon sighting a U-boat within 6,000 yards, the ship heads straight for the U-boat at best speed for 2 minutes. It was expected that the U-boat would fire its acoustic torpedo when it saw the ship heading straight for it.[ Williams (1979). ''Captain Gilbert Roberts'', p. 129: "It was obvious that the U-boat did not fire its acoustic torpedo until it was sure the escort was attacking."] After 2 minutes, the ship turns 60 degrees left or right and holds this divergent course for 3 minutes, thereby putting itself outside the acoustic torpedo's detection range. Then the ship turns to head straight for the U-boat again. If the U-boat has not yet dived, the ship repeats the maneuver: sail towards the U-boat for 2 minutes, then turn 60 degrees, etc. The warship repeats this process until the U-boat dives. When the U-boat dives, the ship rushes to the U-boat's diving position, then slows down to do a sonar search.[''Conduct of anti-U-boat operations'', part 2, Chapter IV, paragraph 381]
(UK National Archives reference ADM 239/298)
See also
* Rodger Winn
Sir Charles Rodger Noel Winn, CB, OBE (22 December 1903 – 4 June 1972) was a British judge and Royal Navy intelligence officer who led the tracking of German U-boat operations during World War II.
Early life
Winn suffered from polio as a c ...
Footnotes
Bibliography
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''Atlantic Convoy Instructions''
* Captain G. H. Roberts C.B.E., R.N. (1947) The Battles of the Atlantic, Royal United Services Institution. Journal, 92:566, 202-215, DOI: 10.1080/03071844709433989 (Archived a
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{{Wargames
Royal Navy in World War II
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