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Proposal: Battle of the Atlantic 75th Anniv
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Posted: Sunday, August 17, 2014 - 11:05 AM UTC
Less than two weeks to go for the campaign launch!
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Posted: Monday, August 18, 2014 - 12:19 AM UTC
BOA – Personality of the Week - Helmut Rosenbaum (11 May 1913 – 10 May 1944)

Helmut Rosenbaum was a corvette captain (or lieutenant commander) in Nazi Germany's Kriegsmarine during World War II who commanded U-boat U-2, U-73 and the 30th U-boat Flotilla. He received the Knight's Cross of the Iron Cross, awarded to recognise extreme battlefield bravery or successful military leadership. He is credited with the sinking of six ships for a total of 35,171 gross register tons (GRT) and three warships.

Born in Döbeln, Rosenbaum joined the Reichsmarine (navy of the Weimar Republic) in 1932. After a period of training on surface vessels and service on various U-boats during the Spanish Civil War, he took command of his first U-boat in 1939. After torpedoing and sinking the HMS Eagleon 11 August 1942, Rosenbaum was appointed commander of the 30th U-boat Flotilla. He was killed in an aircraft crash on 10 May 1944.

Helmut Rosenbaum began his naval career with the Reichsmarine on 15 August 1932 as a late for the year member of "Crew 1932" (the incoming class of 1932). He underwent basic military training in the 2nd department of the standing ship division of the Baltic Sea in Stralsund (15 August 1932 – 7 October 1932).[Tr 1][Tr 2] Rosenbaum was then transferred to the training ship Edith (14 October 1932 – 21 October 1932), attaining the rank of Seekadett (midshipman) on 4 November 1932. Following a 14-month stay on board the light cruiser Köln (6 November 1932 – 2 January 1934) he advanced in rank to Fähnrich zur See (officer cadet) on 1 January 1934. Rosenbaum then underwent a number of officer training courses at the Naval Academy at Mürwik and Kiel-Wik, including navigational training cruises on the tender Weser and Nordsee, before transferring to the cruiser Königsberg (19 April 1935 – 26 September 1935). Following his stay on Königsberg he was promoted to Oberfähnrich zur See (Senior Ensign) on 1 September 1935. Rosenbaum then attended more training courses, including a naval artillery course (27 September 1935 – 3 December 1935) and an anti U-boat defense course (4 December 1935 – 14 December 1935), before being posted to the cruiser Nürnberg (15 December 1935 – 11 October 1936). During this assignment Rosenbaum received his officer's commission holding the rank Leutnant zur See (Second Lieutenant) as of 1 January 1936. His stay on Nürnberg was interrupted in February and March to attend another training course at Kiel-Wik.

Rosenbaum then attended various torpedo courses at the torpedo school in Flensburg from mid October 1936 to end of January 1937. His U-boat training began on 1 February 1937 ending with his assignment as watch officer on U-35 in the Saltzwedel Flotilla on 3 April 1937. U-35 at the time was under the command of Hans Rudolf Rösing.

From 6 August 1940 to 29 September 1940 he attended U-73 construction briefing at the Bremer Vulkan ship yard and commissioned U-73 on 30 September 1940 after completing his first two war patrols on U-2.[Tr 3] He sank one ship on his first patrol on U-73 in the North Atlantic.

On his second patrol (25 March 1941 – 24 April 1941) on U-73 Rosenbaum departed from Lorient and attacked and sank five ships, returning to St. Nazaire after four weeks at sea.[4] He attacked convoy SC 26 on 3 April 1941 sinking the Alderpool, Indier, Westpool, and British Viscount. This achievement earned Rosenbaum a reference on 4 April 1942 in the Wehrmachtbericht (armed forces report), an information bulletin issued by the headquarters of the Wehrmacht. To be singled out individually in this way was an honour and was entered in the Orders and Decorations' section of a soldier's Service Record Book. The British 8,570 GRT Empire Endurance was sunk on 20 April 1941.

In February 1942 U-73 was heavily bombed during his first Mediterranean patrol but nevertheless managed to reach La Spezia. In August 1942, on his eighth and final patrol (4 August 1942 – 5 September 1942) on U-73, Rosenbaum attempted an attack on convoy WS 21S of Operation Pedestal bound for Malta. On 11 August 1942 he made contact and fired four torpedoes at the aircraft carrier HMS Eagle sinking her in the engagement earning him the Knight's Cross of the Iron Cross (Ritterkreuz des Eisernen Kreuzes) on 12 August 1942 and a further reference in the Wehrmachtbericht.

Following his command of U-73 he took command of the 30th U-boat Flotilla on 1 October 1942. At the same time he held the position of Admiralstabsoffizier (Asto—officer of the admiralty staff) in the staff of the Admiral of the Black Sea. Helmut Rosenbaum was killed in an airplane crash on 10 May 1944 near Constanţa in Romania as commander of the 30th U-boat Flotilla. Rosenbaum was on his way to a meeting with the commanding admiral of the Black Sea.[3] Rosenbaum was posthumously promoted to Korvettenkapitän (Corvette Captain) on 3 August 1944 with an effective date as of 1 May 1944.

As a U-boat commander of U-73 Helmut Rosenbaum is credited with the sinking of six merchantmen for a total of 35,171 gross register tons (GRT), and three warships, the HMS Eagle on 11 August 1942, of 22,692 metric tons (22,334 long tons; 25,014 short tons), and two motor launches on board Empire Endurance.
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Posted: Monday, August 18, 2014 - 12:21 AM UTC
BOA - Weapon of the Week - Type VII submarine

From Wikipedia:

Class overview

Name: Type VII

Builders: Neptun Werft, Rostock; Deschimag, Bremen; Germaniawerft, Kiel; Flender Werke, Lübeck; Danziger Werft, Danzig; Blohm + Voss, Hamburg; Kriegsmarinewerft, Wilhelmshaven; Nordseewerke, Emden; F. Schichau, Bremerhaven; Howaldtswerke AG, Kiel

In commission: 1936–1970 (G-7)

Completed: 703

General characteristics (Type VIIC)

Displacement: 769 tonnes (757 long tons) surfaced
871 t (857 long tons) submerged[
Length: 67.1 m (220 ft 2 in) o/a
50.5 m (165 ft 8 in) pressure hull
Beam: 6.2 m (20 ft 4 in)
4.7 m (15 ft 5 in) (pressure hull)
Height: 9.60 m (31 ft 6 in)
Draft: 4.74 m (15 ft 7 in)
Propulsion: 2 × supercharged 6-cylinder 4-stroke diesel engines totalling 2,800–3,200 hp (2,100–2,400 kW). Max rpm: 470-490
Speed: 17.7 knots (32.8 km/h; 20.4 mph) surfaced
7.6 knots (14.1 km/h; 8.7 mph) submerged
Range: 8,500 nautical miles (15,700 km; 9,800 mi) at 10 kn (19 km/h) surfaced
80 nautical miles (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth: 230 m (750 ft)
Calculated crush depth: 250–295 m (820–968 ft)
Complement: 44-52 officers & ratings
Armament: 5 × 53.3 cm (21 in) torpedo tubes (4 bow, 1 stern)
14 × torpedoes or 26 TMA or 39 TMB mines
1 × 8.8 cm SK C/35 naval gun with 220 rounds

Various antiaircraft weaponry:
Type VII U-boats were the most common type of German World War II U-boat. The Type VII was based on earlier German submarine designs going back to the World War I Type UB III and especially the cancelled Type UG, designed through the Dutch dummy company Ingenieurskantoor voor Scheepsbouw den Haag (I.v.S) which was set up by Germany after World War I in order to maintain and develop German submarine technology and to circumvent the limitations set by the Treaty of Versailles, and was built by shipyards around the world. The Finnish Vetehinen class and Spanish Type E-1 also provided some of the basis for the Type VII design. These designs led to the Type VII along with Type I, the latter being built in AG Weser shipyard in Bremen, Germany. The production of Type I was cut down only after two boats; the reasons for this are not certain and range from political decisions to faults of the type. The design of the Type I was further used in the development of the Type VII and Type IX. Type VII submarines were the most widely used U-boats of the war and were the most produced submarine class in history, with 703 built. The type had several modifications.

The Type VII was the most numerous U-boat type to be involved in the Battle of the Atlantic.

Type VIIA:
Type VIIA U-boats were designed in 1933–34 as the first series of a new generation of attack U-boats. Most Type VIIA U-boats were constructed at Deschimag AG Weser in Bremen with the exception of U-33 through U-36, which were built at Friedrich Krupp Germaniawerft, Kiel. Type VIIA U-boats were generally popular with their crews and much more powerful than the smaller Type II U-boats they replaced, with four bow and one external stern torpedo tubes. Usually carrying 11 torpedoes on board, they were very agile on the surface and mounted the 8.8 centimetres (3.5 in) quick-firing deck gun with about 220 rounds.

Ten Type VIIA boats were built between 1935 and 1937. All but two Type VIIA U-boats were sunk during World War II (famous Otto Schuhart U-29 and U-30 which is the first submarine to sink a ship in World War II, both scuttled in Kupfermühlen Bay on 4 May 1945).

The boat was powered on the surface by two MAN AG, 6 cylinder 4-stroke M6V 40/46 diesel engines giving a total of 2,100 to 2,310 brake horsepower (1,570 to 1,720 kW) at 470 to 485 rpm. When submerged it was propelled by two Brown, Boveri & Cie (BBC) GG UB 720/8 electric motors giving a total of 750 horsepower (560 kW) at 322 rpm.

Type VIIB:
The VIIA had limited fuel capacity, so 24 Type VIIB boats were built between 1936 and 1940 with an additional 33 tonnes of fuel in external saddle tanks which added another 2,500 nautical miles (4,600 km; 2,900 mi) of range at 10 knots (19 km/h) surfaced. They were slightly faster than the VIIA, and had two rudders for greater agility. The torpedo armament was improved by moving the aft tube to the inside of the boat. Now an additional aft torpedo could be carried below the deck plating of the aft torpedo room (which also served as the electric motor room) and two watertight compartments under the upper deck could hold two additional torpedoes giving it a total of 14 torpedoes. The only exception was U-83, which lacked a stern tube and carried only 12 torpedoes.

Type VIIBs included many of the most famous U-boats of World War II, including U-48 (the most successful), Prien's U-47, Kretschmer's U-99, and Schepke's U-100.

On the surface the boat was powered by two supercharged MAN, 6 cylinder 4-stroke M6V 40/46 diesels (except for U-45 to U-50, U-83, U-85, U-87, U-99, U-100, and U-102 which were powered by two supercharged Germaniawerft 6-cylinder 4-stroke F46 diesels) giving a total of 2,800–3,200 metric horsepower (2,100–2,400 kW) at 470 to 490 rpm. When submerged, the boat was powered by two AEG GU 460/8-276 (except in U-45, U-46, U-49, U-51, U-52, U-54, U-73 to U-76, U-99 and U-100 which retained the BBC motor of the VIIA) electric motors giving a total of 750 metric horsepower (550 kW) at 295 rpm.[26]

Type VIIC:
The Type VIIC was the workhorse of the German U-boat force, with 568 commissioned from 1940 to 1945.[74] The first VIIC boat commissioned was the U-69 in 1940. The Type VIIC was an effective fighting machine and was seen almost everywhere U-boats operated, although its range of only 6,500 nautical miles was not as great as that of the larger Type IX (11,000 nautical miles), severely limiting the time it could spend in the far reaches of the western and southern Atlantic without refueling from a tender or U-boat tanker.[74] The VIIC came into service toward the end of the "First Happy Time"[Note 6] near the beginning of the war and was still the most numerous type in service when Allied anti-submarine efforts finally defeated the U-boat campaign in late 1943 and 1944.

Type VIIC differed from the VIIB only in the addition of an active sonar and a few minor mechanical improvements, making it 2 feet longer and 8 tons heavier. Speed and range were essentially the same. Many of these boats were fitted with snorkels in 1944 and 1945.

They had the same torpedo tube arrangement as their predecessors, except for U-72, U-78, U-80, U-554, and U-555, which had only two bow tubes, and for U-203, U-331, U-351, U-401, U-431, and U-651, which had no stern tube.

On the surface the boats (except for U-88, U-90 and U-132 to U-136 which used MAN M6V40/46s) were propelled by two supercharged Germaniawerft, 6 cylinder, 4-stroke M6V 40/46 diesels totaling 2,800 to 3,200 hp (2,100 to 2,400 kW) at 470 to 490 rpm.

For submerged propulsion, several different electric motors were used. Early models used the VIIB configuration of two AEG GU 460/8-276 electric motors, totaling 750 hp (560 kW) with a max rpm of 296, while newer boats used two BBC GG UB 720/8, two GL (Garbe, Lahmeyer & Co.) RP 137/c electric motors or two Siemens-Schuckert-Werke (SSW) GU 343/38-8 electric motors with the same power output as the AEG motors.

Perhaps the most famous VIIC boat was U-96, featured in the movie Das Boot.

U-flak "Flak Traps”
The concept of the "U-flak" or "Flak Trap" originated the previous year, on 31 August 1942, when U-256 was seriously damaged by aircraft. Rather than scrap the boat, it was decided to refit her as a heavily armed anti-aircraft boat intended to combat the losses being inflicted by Allied aircraft in the Bay of Biscay. Two 20 mm quadruple Flakvierling mounts and an experimental 37 mm automatic gun were installed on the U-flaks' decks. A battery of 86 mm line-carrying anti-aircraft rockets was tested (similar to a device used by the British in the defense of airfields), but this idea proved unworkable. At times, two additional single 20 mm guns were also mounted. The submarines' limited fuel capacities restricted them to operations only within the Bay of Biscay. Only five torpedoes were carried, preloaded in the tubes, to free up space needed for additional gun crew.

Four VIIC boats were modified for use as surface escorts for U-boats departing and returning to French Atlantic bases. These "U-flak" boats were U-441, U-256, U-621, and U-951. Conversion began on three others (U-211, U-263, and U-271) but none was completed and they were eventually returned to duty as standard VIIC attack boats.

The modified boats became operational in June 1943 and at first appeared to be successful against a surprised Royal Air Force. Hoping that the extra firepower might allow the boats to survive relentless British air attacks in the Bay of Biscay and reach their operational areas, Donitz ordered the boats to cross the bay in groups at maximum speed. The effort earned the Germans about two more months of relatively limited freedom, until the RAF modified their tactics. When a pilot saw that a U-boat was going to fight on the surface, he held off attacking and called in reinforcements. When several aircraft had arrived, they all attacked at once. If the U-boat dived, surface vessels were called to the scene to scour the area with sonar and drop depth charges. The British also began equipping some aircraft with rockets that could sink a U-boat with a single hit, finally making it too dangerous for a U-boat to attempt to fight it out on the surface regardless of its armament. In November 1943, less than six months after the experiment began, it was discontinued. All U-flaks were converted back to standard attack boats and fitted with Turm 4, the standard anti-aircraft armament for U-boats at the time. (According to German sources, only six aircraft had been shot down by the U-flaks in six missions, three by U-441, and one each by U-256, U-621, and U-953.)

Type VIIC/41:
Type VIIC/41 was a slightly modified version of the VIIC and had the same armament and engines. The difference was a stronger pressure hull giving them a deeper test depth and lighter machinery to compensate for the added steel in the hull, making them slightly lighter than the VIIC. A total of 91 were built; all of them from U-1271 onwards lacked the fittings to handle mines.

Today one Type VIIC/41 still exists: U-995 is on display at Laboe (north of Kiel), the only surviving Type VII in the world.
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Posted: Friday, August 22, 2014 - 03:38 AM UTC
One more 'Personality' and 'Weapons' of-the-week entry will be done before the 'Official' thread is started 12:01AM, (Greenwhich mean time).

For any undecideds lurking out there, here's a list of links of BOA related sites from each major naval participant of the battle plus one extra focused on the main weapon of the fight.

Canadian War Museum

The Mariner's Museum

Imperial War Museum


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Posted: Sunday, August 24, 2014 - 02:34 PM UTC
BOA - Personalities of the Week - Commanders Rodger Winn and Kenneth Knowles

During the Battle of the Atlantic, the Allies used intelligence about Axis forces first to safeguard merchant shipping and then as a means of attacking enemy forces with precision. The triumph of Anglo-American cooperation resulted in the solution of Axis codes and ciphers during the war. Intelligence derived from codebreaking provided the Allies with valuable insight into the most sensitive aspects of Axis strategy and operations. At a more tactical level, the information supplied by the Allied codebreakers was most useful when correlated with other intelligence clues about the Axis enemy. Thus, Anglo-American strategists created tracking rooms where all sources of information on Axis submarine and surface vessel movements were compiled. Commanding the submarine tracking rooms of their respective services, Royal Navy Reserve Commander Rodger Winn and U.S. Navy Commander Kenneth Knowles collaborated to maintain a comprehensive intelligence picture of Axis operations in the Atlantic, Indian Ocean, and other naval theaters as well. Together, Winn and Knowles fostered an atmosphere of Anglo-American cooperation that Winn's wartime assistant, Patrick Beesly, once described as "probably closer than between any other British and American organizations in any [s]ervice and in any theater."

To perform their missions, Winn and Knowles correlated information from all sources with highly classified signals intelligence—including information derived from cryptologic special intelligence. Such information was commonly classified under the codenames ULTRA and MAGIC, though other classifications were also used. Always security-conscious, Knowles wrote in April 1945 that "[i]n order to protect sources of information it is strongly recommended that these F-21 and [Admiralty] serials either be destroyed or their security classification raised" to a level of secrecy precluding access "...to various officers and civilian historians who may examine these files." Fortunately, the records were mostly preserved intact and eventually housed in sequestered storage facilities in the United States and Britain.

Winn and Knowles were essential figures in developing and maintaining Anglo-American cooperation during the war. Winn and Knowles first established their war-winning relationship during the Drumbeat crisis of 1942. After Anglo-American intelligence officials negotiated preliminary arrangements to collaborate in collecting special intelligence on Axis forces in April, Knowles was dispatched to work in Winn's tracking room. Studying under Winn in the Admiralty Operational Intelligence Center (OIC), Knowles gained vital experience using Winn's pioneering methods. Returning from Britain to reorganize the U.S. Navy's "Atlantic Section" that fall, Knowles freely shared information and opinions with his British counterpart and friend, Winn. Working together, Winn and Knowles created a forum where British and American strategists could unify the Allied naval command through secure communication. For example, the Admiralty First Sea Lord and U.S. Navy Chief of Naval Operations and Commander in Chief (COMINCH) Admiral Ernest J. King often communicated directly with one another through the secured communiqué transmitted on a daily basis between the Winn and Knowles tracking rooms after 1943.

Many histories depict American leaders like Admiral King as being indecisive during the Drumbeat crisis. However, newly released documents largely undermine negative portrayals of King. Wartime documents clearly reveal King's behind-the-scenes efforts to establish key relationships within the British and American intelligence services. Like his British counterparts, King understood the importance of special intelligence in defeating U-boats. Hoping to develop an intelligence advantage, he placed a high priority on solving the M4 Enigma and aggressively supported U.S. Navy codebreaking and cryptologic efforts with money, personnel, and political clout. King ultimately authorized Knowles to study under Winn in the summer of 1942. By October, King supported a key U.S. Navy codebreaking decision-maker, Commander Joseph Wenger, as he negotiated war-winning arrangements with Royal Navy Captain Edward Travis, Director of GC&CS. Together, they agreed to streamline Allied intelligence gathering. As a result of the Travis and Wenger arrangements of 1942, Anglo-American codebreakers could effectively pool their intellectual and technical resources to solve the four-rotor Enigma and TRITON.

Steadily developing an intelligence advantage, Admiral Ernest J. King, U.S. Navy Chief of Naval Operations and Commander in Chief (COMINCH), met with British and Canadian naval leaders in Washington for the Atlantic Convoy Conference in March 1943. In the conference, King introduced a new Allied strategy, proposing a realignment of authority whereby the British, Canadians, and Americans controlled their own forces in the Atlantic. After some deliberation, the idea was endorsed by the British and Canadian delegations. According to the arrangement, Britain and Canada shared the responsibility of controlling the North Atlantic seaways, while the U.S. Navy assumed control over the central and southern Atlantic. Shortly after the March conference, King created Tenth Fleet. Vessels were not specifically assigned to Tenth Fleet, and the organization essentially served as an antisubmarine command.

At the heart of Tenth Fleet operations, Knowles and his F-21 submarine tracking room staff collected and disseminated the most current operational intelligence on Axis naval operations. Most of the information processed in F-21 was based upon HF/DF and RADAR fixes, rather than just cryptologic sources. Contrary to many post-ULTRA declassification reassessments, Knowles observed in one report that cryptologic intelligence was mostly unavailable on a timely basis for extended periods. He further remarked that "[e]ven when the enemy's cipher is broken, there are many times when the navigational positions are still unreadable." Photographs of the Knowles tracking room illustrate how all the various forms of U-boat tracking information were recorded on the main wall charts in F-21. To limit access to raw cryptologic intelligence, Knowles created the F-211 "Secret Room" as a separate section within F-21. Once cryptologic intelligence was sufficiently sanitized in the confines of the Secret Room, the data was transferred to the main charts in the adjacent F-21 plotting room, where the intelligence could be analyzed and exploited at an operational level.

Once F-21 personnel evaluated and organized the intelligence, the information was customarily transmitted to the Admiralty and, to a lesser extent, the Canadian tracking room in Ottawa. Together, Winn and Knowles worked hard at maintaining current and uniform plots on U-boat locations and dispositions. Meanwhile, the relationship between Winn at the Admiralty and Knowles in F-21 evolved in conjunction with the changes in the Allied war effort in the Atlantic. Under Winn, the Admiralty tracking room continued performing the primary tactical functions of maneuvering convoys away from danger, while Knowles and his F-21 staff provided accurate intelligence to U.S. Navy forces through Tenth Fleet. Eventually, the Americans reshuffled tactical assets, using special intelligence to attack U-boats.

In the central and southern Atlantic, F-21 and Tenth Fleet served as the brains while the ships of the Atlantic Fleet provided the brawn for the U.S. Navy's antisubmarine warfare offensive against Axis submarines. Smaller sized escort carriers were already sailing near Allied convoys, providing air coverage and thwarting U-boat attacks. After 1943, U.S. Navy escort carriers shifted to the offensive. While the British deployed escort carriers with convoys in the North Atlantic, the Americans formed autonomous "hunter-killer" antisubmarine task groups. A typical U.S. Navy hunter-killer task group consisted of a number of escort vessels like Destroyers (DD) and Destroyer Escorts (DE), which were centered on an escort carrier (CVE). Usually, the hunter-killers would sortie from Hampton Roads to a designated operations area. Afterwards, hunter-killer formations would either return to home port or continue on to alternate ports such as those in North Africa for refits, refueling, and rearmament. Maintaining a continuous circuit along the Allied convoy routes and in U-boat operations areas, U.S. Navy hunter-killers were a constant threat to U-boats after 1943.

Maneuvering on intelligence information supplied by the Knowles F-21 tracking room through Tenth Fleet, U.S. Navy hunter-killer task groups attacked concentrations of U-boats in the central and southern Atlantic. Knowles or a member of his F-21 staff customarily met with hunter-killer task group commanders before they embarked on war patrols, providing them with detailed estimates of enemy trends and activity. Over time, Knowles and his F-21 staff developed great rapport with the escort commanders. For security reasons, it was unnecessary for the hunter-killer commanders to have direct access to special intelligence sources. However, Knowles remembered that they regarded F-21 information as "more right than wrong and, therefore, [the hunter-killer commanders] listened very carefully to everything we sent out." Confirming this assessment, one hunter-killer task group commander stated in a postwar assessment that "I treated the [F-21] estimate as Bible truth every day." Thus, with F-21 providing the means for locating and fixing the enemy, U.S. Navy hunter-killers aggressively chased U-boats from Allied convoys and destroyed their logistical support network.

In the summer of 1943, the German naval staff under Admiral Karl Dönitz struggled to support those U-boats that had successfully traversed the Bay of Biscay to reach the open sea. To undermine U-boat logistics, F-21 trackers concentrated hunter-killer attacks against submersible refueling vessels known as "U-tankers." Using all the various forms of special intelligence to establish a constant presence in U-boat resupply areas, F-21 trackers aggressively exploited cryptologic information to destroy the U-tankers. In June 1943, the Germans had a total of nine operational U-tankers. By August 1943, U.S. Navy hunter-killers had sunk eight U-tankers and a number of combat U-boats during refueling operations—always maneuvering on information from F-21.
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Posted: Sunday, August 24, 2014 - 02:37 PM UTC
BOA - Weapon of the week - Hedghog

The Hedgehog (also known as an Anti-Submarine Projector) was an ahead-throwing anti-submarine weapon developed by the Royal Navy of the United Kingdom during World War II. It was deployed on convoy escort warships such as destroyers and corvettes to supplement the depth charge. The weapon fired a number of small spigot mortar bombs from spiked fittings. The bombs exploded on contact, rather than using a time or depth fuze as depth charges did and achieved a higher sinking rate against submarines than depth charges did.

The device was named for the way the rows of empty spigots resembled the spines of a hedgehog.

Based on the British Army's Blacker Bombard 29mm Spigot Mortar, the Hedgehog was developed by the Directorate of Miscellaneous Weapons Development and entered service in 1942.

Hedgehog was replaced in new construction for the Royal Navy by the Squid mortar in 1943, which was in turn replaced by the three-barreled Limbo.

The United States produced a rocket version of Hedgehog called Mousetrap, then Weapon Alpha as a replacement for both. Still, Hedgehog remained in service with the United States Navy into the Cold War until both Hedgehog and the less satisfactory Weapon Alpha were replaced by ASROC.

The Hedgehog was adapted into a seven-shot launcher form for use on the back of the Matilda tank serving with Australian forces.

From 1949, a copy of Hedgehog was produced in the USSR as MBU-200, developed in 1956 into MBU-600 with increased range of 600 meters.

The weapon was a multiple 'spigot mortar' or spigot discharger, a type of weapon developed between the wars by Lt-Col Blacker, RA. The spigot mortar was based on early infantry trench mortars. The spigot design allowed a single device to fire warheads of varying size. The propelling charge was part of the main weapon and worked against a rod (the spigot) set in the baseplate which fitted inside a tubular tail of the 'bomb'. This principle was first used on the Blacker Bombard and the later PIAT anti-tank weapon.

The adaptation of the bombard for naval use was made in partnership with MIR(c) under Major Millis Jefferis who had taken Blacker's design and brought it into use with Army. The weapon fires a salvo of 24 bombs in an arc, aimed to land in a circular or elliptical area about 100 feet (30 m) in diameter at a fixed point about 250 yards (230 m) directly ahead of the attacking ship. The mounting initially was fixed but was later replaced by a gyro-stabilised one to allow for the rolling and pitching of the attacking ship.

The system was developed to solve the problem of the target submarine disappearing from the attacking ships ASDIC when the ship came within the sonar's minimum range. Due to the speed of sound in water, the time taken for the 'ping' echo to return to the attacking ship from the target submarine became too short to allow the human operator to distinguish the returning audible echo from that of the initial sound pulse emitted by the sonar - the so-called 'Instantaneous echo', where the output sound pulse and returning echo merge. This 'blind spot' allowed the submarine to make evasive manoeuvres undetected while the ship was still out of range for depth charge attack, the submarine being effectively invisible to the sonar as the ship came within the sonar's minimum range. The solution was a weapon mounted on the foredeck that discharged the projectiles up and over that carrying ship's bow, to land in the water some distance in front of the ship while the submarine was still outside the sonar's minimum range.

The launcher had four "cradles", each with six launcher spigots. The firing sequence was staggered so all the bombs would land at about the same time. This had the added advantage of minimising the stress on the weapon's mounting, so that deck reinforcement was not needed, and the weapon could easily be retrofitted to any convenient place on a ship. Reloading took about three minutes.

The Hedgehog had four key advantages over the depth charge:

An unsuccessful attack does not hide the submarine from sonar.
When a depth charge explodes it can take 15 minutes before the disturbance can settle down enough that sonar becomes effective. Many submarines escaped during the time after an unsuccessful depth charge attack. Since Hedgehog charges only explode on contact, if they miss, the submarine can still be tracked by sonar.

The depth of the target does not need to be known.
Proximity weapons (such as depth charges) need to be set for the target's correct depth to be effective. Contact fused charges do not have that limitation. In addition, any explosion indicates a "hit".

The weapon gives no warning of the attack.
Until depth-finding sonar became available (the first was the Royal Navy's "Q" attachment in 1943), there was a "dead period" during the final moments of the attack when the attacker had no knowledge of what the target was doing. U-boat commanders became adept at sharp changes of direction and speed at these moments, thus making the attack less accurate. Ahead-thrown weapons such as Hedgehog did not give the target the necessary warning of when to dodge.

A direct hit by one or two Hedgehog bombs was usually sufficient to sink a submarine.
Many depth charges were required in order to inflict enough cumulative damage to sink a submarine; even then, many U-boats survived hundreds of detonations over a period of many hours—678 depth charges were dropped against U 427 in April 1945. The depth charge, usually exploding at a distance from the submarine, had a cushion of water between it and the target which rapidly dissipated the explosive shock. The Hedgehog's contact charge, on the other hand, had the cushion on the other side, actually increasing the explosive shock. However, near misses with the Hedgehog did not cause cumulative damage as depth charges did; nor did it have the same psychological effect as a depth charge attack.

The Hedgehog became much more successful than depth-charge attacks (the best kill rate was about 25% of attacks whereas depth charges never achieved more than 7%). It initially had a very poor record, although many of the factors had nothing to do with the design of the weapon.[citation needed] USS England sank six Japanese submarines in a matter of days with Hedgehog in May 1944.

Specifications for a single bomb:

Calibre: 7 in (178 mm)
Weight: 65 lb (29 kg)
Shell Diameter : 7.2 in (183 mm)
Shell Length: 3 ft 10.5 in (1,181 mm)
Explosive charge: 30 lb (14 kg) TNT or 35 lb (16 kg) Torpex
Range: about 250 yd (230 m)
Sinking speed: 22 to 23.5 ft/s (6.7 to 7.2 m/s)
Fuse: Contact, High Explosive
Firing Order: Ripple in pairs, one every tenth of a second
Reload Time: ~3 minutes

Mark 10: elliptical pattern measuring about 140 by 120 feet (43 m × 37 m) to a range of 200 yards (180 m).
Mark 11: circular pattern measuring 200 feet (61 m) in diameter out to a range of about 188 yards (172 m).
Mark 15: pattern as for the Mark 11 but mounted on a platform adapted from that of a quadruple 40 mm Bofors gun mount. The Mark 15 could be fired remotely from the ship's plotting room.
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Joined: June 18, 2003
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Posted: Sunday, August 31, 2014 - 03:00 PM UTC
That's it for this thread. The build thread is here.

See you on the convoy routes!