Vorpostenboot (plural Vorpostenboote ), also referred to as VP-Boats , flakships or outpost boats , were German patrol boats which served during both World Wars . They were used around coastal areas and in coastal operations, and were tasked with – among other things – coastal patrol, ship escort, and naval combat.
102-677: Vorpostenboote typically carried one or two medium-calibre guns (e.g. 88 mm), many light automatic anti-aircraft guns (20–40 mm), and a varying number of machine guns. For anti-submarine warfare they were also fitted with depth charges . They were crewed by sixty to seventy men, most of whom were weapons personnel taken from the naval reserve. While Vorpostenboote were able to engage and defeat light naval forces – such as small motor gun boats – they were not powerful enough to effectively combat destroyers or larger warships. Some Vorpostenboote (and submarine chasers ) were given heavier AA guns and re-rated as Flakjaeger or Flakkorvetten . At
204-414: A homing torpedo may not be effective. Depth charges are especially useful for "flushing the prey" in the event of a diesel submarine hiding on the bottom. The effective use of depth charges required the combined resources and skills of many individuals during an attack. Sonar, helm, depth charge crews and the movement of other ships had to be carefully coordinated. Aircraft depth charge tactics depended on
306-422: A 120 lb (54 kg) charge for ships too slow to leave the danger area before the more powerful charge detonated. A hydrostatic pistol actuated by water pressure at a pre-selected depth detonated the charge. Initial depth settings were 40 or 80 ft (12 or 24 m). Because production could not keep up with demand, anti-submarine vessels initially carried only two depth charges, to be released from
408-451: A German-controlled area to escape Luftwaffe bombers. The ships were captured and the trawlers were pressed into service as Friese , Salier , and Franke . Even though the invasion and occupation of Norway and Denmark consumed the bulk of available Vorpostenboote , patrols in the North Sea had to continue in order to keep U-boat routes safe and clear of mines. With reduced numbers,
510-941: A chute at the stern of the ship. The first success was the sinking of U-68 off County Kerry , Ireland, on 22 March 1916, by the Q-ship Farnborough. Germany became aware of the depth charge following unsuccessful attacks on U-67 on 15 April 1916, and U-69 on 20 April 1916. The only other submarines sunk by depth charge during 1916 were UC-19 and UB-29 . Numbers of depth charges carried per ship increased to four in June 1917, to six in August, and 30–50 by 1918. The weight of charges and racks caused ship instability unless heavy guns and torpedo tubes were removed to compensate. Improved pistols allowed greater depth settings in 50 ft (15 m) increments, from 50 to 200 ft (15 to 61 m). Even slower ships could safely use
612-400: A coastal convoy . The blockade runner , an Italian tanker SS Butterfly , was escorted by Vorpostenboote Carl J. Busch and Pilote XIII and two submarine chasers . Almost immediately after the destroyers closed with the convoy, at around three in the morning, Pilote was hit by a shell on its stern. As fire was concentrated on the small ship, it fired back with its 88mm gun landing
714-431: A depth charge undergoes a rapid chemical reaction at an approximate rate of 26,000 ft/s (8,000 m/s). The gaseous products of that reaction momentarily occupy the volume previously occupied by the solid explosive, but at very high pressure. This pressure is the source of the damage and is proportional to the explosive density and the square of the detonation velocity. A depth charge gas bubble expands to equalize with
816-401: A device intended for countermining , a "dropping mine". At Admiral John Jellicoe 's request, the standard Mark II mine was fitted with a hydrostatic pistol (developed in 1914 by Thomas Firth and Sons of Sheffield) preset for 45 ft (14 m) firing, to be launched from a stern platform. Weighing 1,150 lb (520 kg), and effective at 100 ft (30 m), the "cruiser mine" was
918-456: A direct hit on Albrighton 's bridge. A British MTB closed on Pilote , which it engaged with its 37mm gun until a direct hit killed the gun crew. Pilote 's captain ordered the ship to be abandoned, but before the order could be carried out a burst of machine gun fire killed him and several other men. The survivors continued to attempt to save their ship. At dawn, the battle expanded to the air, with two dozen Czech-piloted Spitfires strafing
1020-474: A dozen instances where MTBs intercepted and attacked convoys and minesweeping flotillas. Despite being escorted by multiple Vorpostenboote , these engagements often led to the sinking of minesweepers or merchant ships; in just the week of 13 March, five large steamers were sunk by MTBs. British destroyers, bolstered by the new MTBs, made more daring attacks on German shipping as well. In late April 1943, HMS Albrighton and HMS Goathland launched an attack on
1122-522: A handful of new formations which incorporated Vorpostenboote , such as the KSV norwegische Westküste in Bergen . Initially, the command consisted of just four fishing ships and two Vorpostenboote , but it would eventually expand to 45 vessels spread between three Vp-flotillas and a minesweeper flotilla. The Kriegsmarine were not the only ones who were unprepared for this new situation. Britain's RAF Coastal Command
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#17328762507971224-406: A killing radius (resulting in a hull breach) of only 10–13 ft (3–4 m) against a conventional 1000-ton submarine, while the disablement radius (where the submarine is not sunk but is put out of commission) would be approximately 26–33 ft (8–10 m). A larger payload increases the radius only slightly because the effect of an underwater explosion decreases as the cube of the distance to
1326-533: A more effective average depth of 246 ft (75 m). Vice Admiral Charles A. Lockwood , commander of the U.S. submarine fleet in the Pacific, later estimated that May's ill-advised comments cost the US Navy as many as ten submarines and 800 seamen killed in action . For the reasons expressed above, the depth charge was generally replaced as an anti-submarine weapon. Initially, this was by ahead-throwing weapons such as
1428-588: A patrol plane or deployed by an anti-submarine missile from a surface ship, or another submarine, located a safe distance away. By the late 1990s all nuclear anti-submarine weapons had been withdrawn from service by the United States , the United Kingdom , France , Russia and China . They have been replaced by conventional weapons whose accuracy and range had improved greatly as ASW technology improved. The first attempt to fire charges against submerged targets
1530-463: A period of many hours, such as U-427 , which survived 678 depth charges in April 1945. The first delivery mechanism was to simply roll the "ashcans" off racks at the stern of the moving attacking vessel. Originally depth charges were simply placed at the top of a ramp and allowed to roll. Improved racks, which could hold several depth charges and release them remotely with a trigger, were developed towards
1632-611: A potential hazard to the dropping ship. The design work was carried out by Herbert Taylor at the RN Torpedo and Mine School, HMS Vernon . The first effective depth charge, the Type D, became available in January 1916. It was a barrel-like casing containing a high explosive (usually TNT , but amatol was also used when TNT became scarce). There were initially two sizes—Type D, with a 300 lb (140 kg) charge for fast ships, and Type D* with
1734-499: A prolonged period of time coupled with Allied bombing of harbors and drydocks. In an attempt to solve this problem, nine converted whalers from the 17th Vp-flotilla were transferred from Skagerrak to the Gulf of Finland . This meant that there were fewer vessels available to intercept blockade runners going to or from Sweden, and a reduced presence along the Swedish coastline. On 6 June 1944,
1836-528: A third flotilla be transferred to the North Sea, which was denied due to a lack of ships and manpower. During the invasions of Norway and Denmark in April 1940, Vorpostenboote continued their patrol duties and also escorted landing groups and tankers in ten convoys. In Denmark, few of these operations were contested, but in Norway there was resistance by submarines and surface ships. Submarines were particularly dangerous, The British submarine HMS Triton attacked
1938-461: A torpedo into the boat, causing an explosion which tore the ship in two. The 7th Vp-flotilla had been completely destroyed, and on 20 September it was formally disbanded. From this point on, the remaining flotillas had little naval action besides sitting in port in the coastal fortresses which were under siege. Occasionally, single or small groups of Vorpostenboote made patrols of the harbor entrances to dissuade landings or incursions. However, this
2040-440: A wider dispersal pattern when used in conjunction with rack-deployed charges. The first of these was developed from a British Army trench mortar . 1277 were issued, 174 installed in auxiliaries during 1917 and 1918. The bombs they launched were too light to be truly effective; only one U-boat is known to have been sunk by them. Thornycroft created an improved version able to throw a charge 40 yd (37 m). The first
2142-531: Is an anti-submarine warfare (ASW) weapon designed to destroy submarines by detonating in the water near the target and subjecting it to a destructive hydraulic shock . Most depth charges use high explosives with a fuze set to detonate the charge, typically at a specific depth from the surface. Depth charges can be dropped by ships (typically fast, agile surface combatants such as destroyers or frigates ), patrol aircraft and helicopters . Depth charges were developed during World War I , and were one of
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#17328762507972244-554: Is detonated at a shallow depth and the gas bubble vents into the atmosphere very soon after the detonation are quite ineffective, even though they are more dramatic and therefore preferred in movies. A sign of an effective detonation depth is that the surface just slightly rises and only after a while vents into a water burst. Very large depth charges, including nuclear weapons, may be detonated at sufficient depth to create multiple damaging shock waves. Such depth charges can also cause damage at longer distances, if reflected shock waves from
2346-481: The 90SG . China has also produced such weapons. During the Cold War when it was necessary to inform submarines of the other side that they had been detected but without actually launching an attack, low-power "signalling depth charges" (also called "practice depth charges") were sometimes used, powerful enough to be detected when no other means of communication was possible, but not destructive. The high explosive in
2448-702: The Austro-Hungarian Navy access to the Mediterranean. On 15 May 1917, the Austro-Hungarian Navy raided the barrage . The Austro-Hungarians gave most drifter crews warning to abandon ship before opening fire. Some drifter crews chose to fight, and the Gowan Lee returned fire on the Austro-Hungarian ships. The drifter was heavily damaged, but remained afloat. Skipper Joseph Watt was later awarded
2550-519: The Battle of Pierres Noires , Canadian destroyers of Escort Group 12 detected on radar a group leaving Brest. It was two U-boats being escorted by the Vorpostenboote Alfred I , Vierge de Nassabielle , Leipzig , and Marie Simone along with two minesweepers. The Allied ships' opening salvo struck Alfred I , disabling its rudders and setting it ablaze. The U-boats managed to dive and escape
2652-484: The Battle of the Atlantic directive, which sought to reduce the ability of Germany's surface fleet to raid commerce. These bombing missions were increasingly effective, and in one instance, Gneisenau was torpedoed on 28 March, went into drydock, and was again bombed on 10 April. The air raids continued throughout 1941 and into 1942, with 37 percent of Bomber Command sorties between 10 December and 20 January 1942 targeting
2754-400: The Battle of the Atlantic wore on, British and Commonwealth forces became particularly adept at depth charge tactics, and formed some of the first destroyer hunter-killer groups to actively seek out and destroy German U-boats. Surface ships usually used ASDIC ( sonar ) to detect submerged submarines. However, to deliver its depth charges a ship had to pass over the contact to drop them over
2856-524: The German Minesweeping Administration was formed by the Allies under Royal Navy control from Kriegsmarine sailors and vessels. At least five former Vorpostenboote were included in nearly 300 vessels carrying out mine clearing sorties, which resulted in the disarming of 2721 mines by the time it was replaced by a civilian organisation in January 1948. Depth charge A depth charge
2958-515: The Heligoland Bight on 20 November , escaping without detection. Thick ice in the Baltic and rough sea conditions in the North Sea continued to hamper patrolling operations into 1940. In an attempt to combat these poor conditions, naval drifters in the North Sea were transferred to the Baltic, and trawlers from the Baltic were transferred to the North Sea. The drifters were better able to break up
3060-642: The House Military Affairs Committee caused The May Incident . The congressman, who had just returned from the Pacific theater where he had received confidential intelligence and operational briefings from the US Navy, revealed at a press conference that there were deficiencies in Japanese depth-charge tactics. After various press associations reported the depth issue, the Japanese Imperial Navy began setting their depth charges to explode at
3162-475: The Royal Navy requisitioned many fishing drifters for conversion to naval use during World War I . In addition, 362 naval drifters were ordered to Admiralty specifications (and thus are often referred to as "Admiralty drifters"). Shipyards used to building fishing trawlers or drifters could easily switch to constructing naval versions. As a bonus these drifters could be sold to commercial fishing interests when
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3264-543: The SUBROC , which was armed with a nuclear depth charge. The USSR , United States and United Kingdom developed nuclear depth bombs . As of 2018 , the Royal Navy retains a depth charge labelled as Mk11 Mod 3, which can be deployed from its AgustaWestland Wildcat and Merlin HM.2 helicopters . Russia has also developed homing (but unpropelled) depth charges including the S3V Zagon and
3366-427: The 13th flotilla, while coasters made up the 10th flotilla. The 12th and 15th flotillas consisted of a combination of whalers and trawlers, and the 1st flotilla was made up of eight steamers which would later be converted into Sperrbrecher mine clearance vessels. Several Vorpostenboote were lost in the harsh winter of 1939, in part due to mines (called "drifters") which had been broken free from their moorings by
3468-477: The 1930s, these trawlers also grew in tonnage, and 400 GRT ships were the standard by the end of the decade. By 1937, the Kriegsmarine began actively commissioning trawlers for the express purpose of converting them into Vorpostenboote , hoping to standardize the design and minimize the time it would take to convert the civilian ships into warships. The first operational Vorpostenboote flotilla ( Vp-Flotilla )
3570-509: The 2nd convoy, which consisted of the transport ships Friedenau and Wigbert and a heavy escort of Vorpostenboote and minesweepers. Triton spotted the convoy on the afternoon of 10 April and sank both transport ships and Vorpostenboot Rau VI , resulting in the drowning of more than 900 German soldiers . Despite launching more than 70 depth charges, the convoy was unable to sink the Triton which escaped with only minor damage. Following
3672-618: The Allied liberation of the European mainland began with the Normandy landings of Operation Neptune. Standing against the overwhelming naval strength of the Allied forces were 163 minesweepers, 42 Artillerieträger [ de ] , and 57 Vorpostenboote . Early on the morning of D-Day, British glider-borne soldiers captured what is now called Pegasus Bridge , a key canal bridge at Bénouville which would prevent German reinforcements from reaching
3774-476: The Baltic Sea. There was resistance to this activity by Soviet surface ships, especially in the Gulf of Riga . One convoy escorted by Vorpostenboote was attacked by a large Soviet force of four MTBs, various aircraft, the cruiser Kirov and its supporting destroyers. The attack only managed to sink the landing ship Deutschland , inflicting minor damage on several other escort ships. Similar attempts to contest
3876-623: The Baltic were ultimately unsuccessful, but did serve to slow the German advance and prevent total control of the sea. The capitulation of France allowed for an increase in commerce raiding by German warships against British shipping. Following successful raids in the North Sea, the German capital ships Scharnhorst , Gneisenau , and Prinz Eugen ended up in port at Brest in Brittany for repairs and maintenance. The ships began to be harassed in port by British air attacks after Winston Churchill issued
3978-667: The British Commandos were withdrawing back across the Channel, one of their motor launches , ML 306 , was intercepted by the German torpedo boat Jaguar . The torpedo boat attacked ML 306 , closing to short range and boarding the vessel, capturing it. The motor launch was later brought back to a German port by Sachsenwald and Gotland . By summer of 1942, Kriegsmarine auxiliaries were still in short supply in almost every theater of combat. Large numbers of minelayers were needed to ensure that
4080-532: The British and Canadian beachheads. Two small German ships, whose identity has been attributed to Vorpostenboote Otto Bröhan and Friedrich Busse , steamed up the canal and counterattacked against the British forces now defending the bridge. The attack was ineffectual, causing only one minor injury, and eventually both ships were scuttled in the Caen Canal . While a few Vorpostenboote attempted to make contact with
4182-576: The British-developed Hedgehog and later Squid mortars. These weapons threw a pattern of warheads ahead of the attacking vessel to bracket a submerged contact. The Hedgehog was contact fuzed, while the Squid fired a pattern of three large, 440 lb (200 kg) depth charges with clockwork detonators. Later developments included the Mark 24 "Fido" acoustic homing torpedo (and later such weapons), and
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4284-605: The German convoy before being engaged by Luftwaffe fighters. Pilote again bore the brunt of this attack. However, only one bomb - which did not explode - struck the ship, damaging its engine ventilators and smokestack. When British ships and aircraft finally began to disengage at around six in the morning, one of the submarine chasers had been sunk, SS Butterfly was breaking up, and the Pilote had taken heavy casualties. Of its forty-one crew, eighteen were dead and nineteen injured, leaving only four men unharmed. Despite these losses, Pilote
4386-785: The Kriegsmarine was fielding only a quarter of the convoy escorts as had been demanded in 1940. The problems the Kriegsmarine faced were worsened by the American entry into World War II . The start of American naval involvement in Europe was marked on 19 February 1943, when the USS Blackfish steamed into the Bay of Biscay . That afternoon, Blackfish spotted two Vorpostenboote , V 404 and Haltenbank . Recognizing their German colors, Blackfish launched two torpedoes at Haltenbank , one of which hit and sank
4488-545: The Low Countries, and Norway, the Kriegsmarine had a coastline from the Arctic to Spain to protect. This entire stretch had to be cleared of existing mines, patrolled, and protected from submarines or re-mining. The demands of this task led to a major restructuring of the auxiliary navy, with new commands being established and new ships requisitioned and commissioned. Most of these were minesweepers and Sperrbrecher , but there were
4590-535: The RN, and 16,451 fired, scoring 38 kills in all, and aiding in 140 more. The United States requested full working drawings of the device in March 1917. Having received them, Commander Fullinwider of the U.S. Bureau of Naval Ordnance and U.S. Navy engineer Minkler made some modifications and then patented it in the U.S. It has been argued that this was done to avoid paying the original inventor. The Royal Navy Type D depth charge
4692-539: The Soviets were not able to re-establish themselves in the Baltic Sea by slipping submarines through German lines. The 3rd and 17th Vp-flotillas were engaged in this task from 25 April, under the command of the Marineverbindungsstab Finnland . These activities, along with the many other responsibilities of the Kriegsmarine auxiliary commands, drew away ships and manpower from convoy escort duty. By this point,
4794-445: The Type D at below 100 ft (30 m) and at 10 kn (19 km/h; 12 mph) or more, so the relatively ineffective Type D* was withdrawn. Monthly use of depth charges increased from 100 to 300 per month during 1917 to an average of 1745 per month during the last six months of World War I . The Type D could be detonated as deep as 300 ft (90 m) by that date. By the war's end, 74,441 depth charges had been issued by
4896-464: The Y-gun as the primary depth charge projector. The K-guns fired one depth charge at a time and could be mounted on the periphery of a ship's deck, thus freeing valuable centerline space. Four to eight K-guns were typically mounted per ship. The K-guns were often used together with stern racks to create patterns of six to ten charges. In all cases, the attacking ship needed to be moving fast enough to get out of
4998-799: The addition of a streamlined nose fairing and stabilising fins on the tail; it entered service in 1941 as the Mark VII Airborne DC. Other designs followed in 1942. Experiencing the same problems as the RAF with ineffective anti-submarine bombs, Captain Birger Ek of Finnish Air Force squadron LeLv 6 contacted a navy friend to use Finnish Navy depth charges from aircraft, which led to his unit's Tupolev SB bombers being modified in early 1942 to carry depth charges. Later depth charges for dedicated aerial use were developed. These are still useful today and remain in use, particularly for shallow-water situations where
5100-399: The aircraft using its speed to rapidly appear from over the horizon and surprising the submarine on the surface (where it spent most of its time) during the day or night (at night using radar to detect the target and a Leigh light to illuminate it immediately before attacking), then quickly attacking once it had been located, as the submarine would normally crash dive to escape attack. As
5202-507: The battle, and the German escorts returned fire, eventually driving the Allied ships away. However, Vierge de Nassabielle and Marie Simone were both badly damaged, and Alfred I had to be abandoned and would eventually sink. Similar attacks continued throughout July, and in August what little forces the Kriegsmarine had remaining in western France were utterly destroyed in Operation Kinetic . In total, 62 auxiliary ships were sunk over
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#17328762507975304-672: The capital ships. Vorpostenboote were to act as minesweepers and outpost boats placed along the route of the convoy. VP boats began their involvement in the operation well before any ships left Brest; ships of the 20th Vp-flotilla began mine clearing to open safe passageways through the Channel in the days leading up to the Dash. On 11 February, the Channel Dash, code named Operation Cerberus, began. Three full flotillas of Vorpostenboote (the 13th, 15th, and 18th) along with five minesweeper flotillas and three Räumboot flotillas were stationed along
5406-515: The capture of Norwegian coastal areas and harbors, German auxiliary naval forces were spread extremely thin. Even at the beginning of the war, the Kriegsmarine had a barebones amount of patrol ships and minesweepers, and the defense and patrol of the Norwegian and Danish coasts would require a sharp increase in ships and manpower. The Kriegsmarine quickly began to press captured Norwegian vessels into service, but these were inadequate in number. Compounding
5508-560: The case of the newly bolstered 4th flotilla, it was considered that Italian personnel could take control of the ships. The commander of the 4th flotilla staunchly opposed this move, and instead only half the crew were replaced with Italians who remained under German command. In the Baltic, the struggle to contain Soviet submarines continued. Surface operations in the Eastern Baltic had been almost completely stopped due to very poor sea state over
5610-401: The closing British ships. Neubau 240 and Neubau 308 quickly ran aground, continuing to fire until incoming shells forced them to abandon ship. Alfred III and Neubau 168 were pounded with shellfire while grounded on a reef within sight of shore; Neubau 168 was sunk and Alfred III raised the white flag in surrender. HMS Ursa moved to capture the ship, but HMCS Iroquois launched
5712-423: The course of the three-week-long offensive. The most devastating moments during the offensive occurred on 23 August during the defense of Brest, when seven Vorpostenboote of the 7th Vp-flotilla were ordered to break out from the harbor and head south to Lorient . The ships set out in two groups, and the first (consisting of Memel , Marie Simone , and Michel François ) were almost immediately detected by
5814-452: The danger zone before the charges exploded. Depth charges could also be dropped from an aircraft against submarines. At the start of World War II, Britain's primary aerial anti-submarine weapon was the 100 lb (45 kg) anti-submarine bomb, but it was too light to be effective. To replace it, the Royal Navy's 450 lb (200 kg) Mark VII depth charge was modified for aerial use by
5916-457: The end of the First World War . These racks remained in use throughout World War II because they were simple and easy to reload. Some Royal Navy trawlers used for anti-submarine work during 1917 and 1918 had a thrower on the forecastle for a single depth charge, but there do not seem to be any records of it being used in action. Specialized depth charge throwers were developed to generate
6018-533: The end of the year four Sicherungsdivision s (Security Divisions) were established and steadily growing in size. Each of these consisted of five or six flotillas, of which one or two were Vp-flotillas . In June 1941, Germany turned east and invaded the Soviet Union in Operation Barbarossa . As this would primarily be a land war, the Kriegsmarine would play only a minor role in the invasion. Its main goal
6120-581: The enemy during the landings, these all had little or no effect due to the overwhelming Allied naval and aerial supremacy. By July, surface resistance by the Germans was effectively non-existent, and the Royal Navy began to turn its attention to destroying the remaining German vessels still operating on the French coast. On 5 July, Operation Dredger was launched, which targeted auxiliary vessels which were escorting U-boats into and out of harbor. The operation resulted in
6222-562: The entire period of the Battle of France, only a single Vorpostenboot was lost, when the Bayern struck a mine in the North Sea on 9 June. Once the Dutch capitulated, the Kriegsmarine immediately began evaluating captured trawlers for their suitability to be converted into minesweepers and Vorpostenboote . More than 300 suitable vessels were identified, which would be necessary to clear mines from and defend
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#17328762507976324-491: The first viable methods of attacking a submarine underwater. They were widely used in World War I and World War II , and remained part of the anti-submarine arsenals of many navies during the Cold War , during which they were supplemented, and later largely replaced, by anti-submarine homing torpedoes . A depth charge fitted with a nuclear warhead is also known as a " nuclear depth bomb ". These were designed to be dropped from
6426-488: The flotillas in the North Sea were susceptible to attack from British bombers and mines. The Hugo Homann fell victim to both these hazards: it was sunk by bombers on 15 April, salvaged and returned to service, and then promptly struck a mine and sunk on 6 May. During the invasion of the Netherlands , Belgium and the Battle of France , Vorpostenboote mostly continued their usual duties without much interruption. During
6528-565: The foul weather. Ships sunk by these rogue mines included the Skolpenbank , Este , and Weser . The loss of the Skolpenbank led to the Seekriegsleitung (SKL, "Naval Warfare Command") clamping down on the amount of classified information carried on auxiliary vessels, since its wreck was never located and there was no way of knowing if information had fallen into enemy hands. Also during
6630-460: The full route of the Dash. Because these boats could not keep up with the main convoy, they would meet it at strategic points where British intercepts were expected. There, they would provide guidance, outpost support, minesweeping, and flak cover to deter and distract air attacks. Operation Cerberus was an overwhelming success for the Germans. All three capital ships made it through the Channel with only minimal damage sustained, and only one escort ship
6732-454: The ice, while the trawlers were still capable of holding up to rough sea conditions. However, this led to an overall reduction of ships patrolling the North Sea; only sixteen trawlers in two flotillas were operational at this time. The Befehlshaber der Sicherung West [ de ] (Commander in Chief of Security West), under whose jurisdiction the North Sea patrols fell, repeatedly demanded
6834-421: The island of Piirissaar , German troops were trapped and required evacuation. On 21 August, four Artillerieträger and two Vorpostenboote provided covering fire for the evacuation. By the end of the war, the Kriegsmarine's auxiliary forces were almost completely annihilated. However, some of the operations which Vorpostenboote were responsible for continued past 1945, especially minesweeping. On 21 June 1945,
6936-498: The larger shipbuilders were unable to continue construction. As such, few trawlers were constructed during this period. However, with the rise of the Nazis , the few remaining companies experienced a major financial boost. Trawler production was revitalized, and new ships which would eventually become Vorpostenboote were built, such as the Carl Röver and R. Walther Darré . Throughout
7038-536: The latest United States Navy submarines could dive so deep. Unless caught in shallow water, an American submarine could dive below the Japanese depth charge attack. The Japanese had used attack patterns based on the older United States S-class submarines (1918–1925) that had a test depth of 200 ft (61 m); while the WWII Balao-class submarines (1943) could reach 400 ft (120 m). This changed in June 1943 when U.S. Congressman Andrew J. May of
7140-429: The light cruiser HMS Mauritius with two destroyers. The group scattered: Memel and Michel François ran aground and Marie Simone was destroyed ship as it attempted to make for shore. Shortly thereafter, the last four Vorpostenboote ( Neubau 168 , Neubau 240 , Neubau 308 , Alfred III ) were detected. This group was better armed and armored, and in the early hours of 24 August laid down smoke and opened fire on
7242-535: The maximum detonation depth to 900 ft (270 m). The Mark VII's 290 lb (130 kg) amatol charge was estimated to be capable of splitting a 7 ⁄ 8 in (22 mm) submarine pressure hull at a distance of 20 ft (6 m), and forcing the submarine to surface at twice that. The change of explosive to Torpex (or Minol) at the end of 1942 was estimated to increase those distances to 26 and 52 ft (8 and 16 m). The British Mark X depth charge weighed 3,000 lb (1,400 kg) and
7344-504: The objective of destroying the large dock there and so prevent any large German warships from using it. German ships could only get to German ports by running the gauntlet of the Royal Navy and so Germany would not risk sending the battleship Tirpitz into the Atlantic to attack convoys. During the raid, the Vorpostenboote Sachsenwald and Gotland were on picket duty offshore between Noirmoutier and Saint-Nazaire. When
7446-428: The ocean floor or surface converge to amplify radial shock waves. Submarines or surface ships may be damaged if operating in the convergence zones of their own depth charge detonations. The damage that an underwater explosion inflicts on a submarine comes from a primary and a secondary shock wave. The primary shock wave is the initial shock wave of the depth charge, and will cause damage to personnel and equipment inside
7548-528: The outset of World War I, the Imperial German Navy lacked sufficient numbers of warships to perform auxiliary tasks like coastal patrol and convoy escort. As such, the navy requisitioned a large portion of civilian fishing trawlers to perform these tasks, converting them into Vorpostenboote . After World War I, Germany's shipbuilding industry suffered because of the Great Depression , and many of
7650-424: The pressure of the surrounding water. This gas expansion propagates a shock wave. The density difference of the expanding gas bubble from the surrounding water causes the bubble to rise toward the surface. Unless the explosion is shallow enough to vent the gas bubble to the atmosphere during its initial expansion, the momentum of water moving away from the gas bubble will create a gaseous void of lower pressure than
7752-406: The problem, the complex and tangled jurisdictions of the German naval commands meant that almost all drifters and trawlers requisitioned at this time were sent to the Baltic Sea rather than being used to guard the Norwegian coast. There were a few minor windfalls for the stretched auxiliary forces, however, such as on 5 May when three British armed trawlers and a Norwegian torpedo boat ran aground in
7854-511: The recently captured French, Dutch, and Belgian harbors. Once the new front in the West was opened, pressure on Norway eased significantly. However, British submarines were still laying mines and harassing vessels off the coast. In May, Antares fell victim to a mine and in June HMS Snapper ambushed a merchant convoy and sank Vorpostenboot Portland . Following the capitulation of France,
7956-527: The results of cracking German ciphers such as the Enigma codes . The greater threat posed by aircraft led to a gradual increase in anti-aircraft armaments carried on Vorpostenboote as the war went on, ultimately resulting in them being dubbed "flak ships" by Allied aviators. Despite the growing capabilities of the British, total numbers of auxiliary warships in the Kriegsmarine continued to grow through 1941. The Security Forces underwent another reorganization, and by
8058-508: The secondary shock wave can be reinforced if another depth charge detonates on the other side of the hull in close time proximity to the first detonation, which is why depth charges are normally launched in pairs with different pre-set detonation depths. The killing radius of a depth charge depends on the depth of detonation, the payload of the depth charge and the size and strength of the submarine hull. A depth charge of approximately 220 lb (100 kg) of TNT (400 MJ ) would normally have
8160-627: The ship. At the same time, the British were also becoming a greater threat in the English Channel and along the Belgian and Dutch coast. The newly developed Fairmile D was larger and better armed than preceding motor torpedo boats (MTB) and motor gun boats, and was designed for combat with German patrol craft. Armed with this new ship, British offensive actions became increasingly common. These attacks were often costly for both sides, both in manpower and material. During March 1943, there were at least half
8262-553: The ships at Brest. At the same time, Adolf Hitler was convinced that the ships at Brest were required in the North Sea to contest an expected British invasion of Norway. Against the advice of his advisors, he demanded the ships make a surprise dash through the English Channel to safety in German-controlled ports. Such a move would require extensive Luftwaffe and escort ship coverage to prevent British air sorties from sinking
8364-588: The stern; sonar contact would be lost just before attack, rendering the hunter blind at the crucial moment. This gave a skilful submarine commander an opportunity to take evasive action. In 1942 the forward-throwing "hedgehog" mortar, which fired a spread salvo of bombs with contact fuzes at a "stand-off" distance while still in sonar contact, was introduced, and proved to be effective. In the Pacific Theater during World War II , Japanese depth charge attacks were initially unsuccessful because they were unaware that
8466-400: The submarine if detonated close enough. The secondary shock wave is a result of the cyclical expansion and contraction of the gas bubble and will bend the submarine back and forth and cause catastrophic hull breach, in a way that can be likened to bending a plastic ruler rapidly back and forth until it snaps. Up to sixteen cycles of secondary shock waves have been recorded in tests. The effect of
8568-400: The surrounding water. Surrounding water pressure then collapses the gas bubble with inward momentum causing excess pressure within the gas bubble. Re-expansion of the gas bubble then propagates another potentially damaging shock wave. Cyclical expansion and contraction can continue for several seconds until the gas bubble vents to the atmosphere. Consequently, explosions where the depth charge
8670-408: The target, a U-boat's pressure hull would not rupture unless the charge detonated within about 15 ft (5 m). Getting the weapon within this range was a matter of luck and quite unlikely as the target took evasive action. Most U-boats sunk by depth charges were destroyed by damage accumulated from an extended barrage rather than by a single charge, and many survived hundreds of depth charges over
8772-759: The target. Naval drifter A naval drifter is a boat built along the lines of a commercial fishing drifter but fitted out for naval purposes. The use of naval drifters is paralleled by the use of naval trawlers . Fishing trawlers were designed to tow heavy trawls, so they were easily adapted to tow minesweepers, with the crew and layout already suited to the task. Drifters were robust boats built, like trawlers, to work in most weather conditions, but designed to deploy and retrieve drift nets . They were generally smaller and slower than trawlers. If requisitioned by navies, they were typically armed with an anti-submarine gun and depth charges and used to maintain and patrol anti-submarine nets. Like fishing trawlers,
8874-467: The war ended. There were two basic types of Admiralty-built drifters, wooden hulled and steel hulled. Royal Navy drifters were named like the trawlers were, except for the Canadian-built vessels which were numbered CD 1 to CD 100. During 1917, a fleet of British drifters, escorted by destroyers and light cruisers, maintained a blockade of the 72 km (45 mi) wide Strait of Otranto , denying
8976-489: The west of the continent due to very poor weather conditions. When V 1411 attempted to put out, it ran aground and nearly capsized. At this time, the focus of Vp-flotillas became strengthening the Atlantic Wall : laying mines and defending "fortresses" along the coast. To that end, several flotillas were strengthened with armed trawlers from other units. However, there was insufficient German manpower to crew these ships. In
9078-457: The winter, British submarine presence in the Baltic Sea increased, leading to several encounters with Vorpostenboote . While several depth charge attacks on the submarines were recorded, they were unsuccessful; on the other hand, British submarines were able to successfully attack and sink multiple Vorpostenboote . One instance of this was when HMS Sturgeon sank V 209 Gauleiter Telschow in
9180-521: Was 200 lb (91 kg) of Torpex with a sinking speed of 14.4 ft/s (4.4 m/s) and depth settings of up to 600 ft (180 m). Later versions increased depth to 1,000 ft (300 m) and sinking speed to 22.7 ft/s (6.9 m/s) with increased weight and improved streamlining. Although the explosions of the standard United States 600 lb (270 kg) Mark 4 and Mark 7 depth charge used in World War II were nerve-wracking to
9282-525: Was able to disengage from the battle, limping into the port of Brest later that day. The ship had sustained more than 140 shell hits and 600 holes from machine gun fire. On top of growing external threats, Kriegsmarine auxiliary ships also became the target of internal unrest. Denmark, whose occupation to this point had been relatively unopposed, experienced several dockyard strikes which affected five Vorpostenboote . The first months of 1944 saw minimal action from Vorpostenboote and other auxiliary ships to
9384-401: Was attacked 26 times, resulting in the sinking of a freighter, Vorpostenboot Natter , and four other auxiliary vessels. In August, two Artillerieträger and five Vorpostenboote set out to contest Soviet landings between Lake Peipus and Lake Pleskau . The flotilla successfully engaged Soviet land batteries and landed troops, and the German defenders were able to push back their advance. On
9486-508: Was designated the "Mark VII" in 1939. Initial sinking speed was 7 ft/s (2.1 m/s) with a terminal velocity of 9.9 ft/s (3.0 m/s) at a depth of 250 ft (76 m) if rolled off the stern, or upon water contact from a depth charge thrower. Cast iron weights of 150 lb (68 kg) were attached to the Mark VII at the end of 1940 to increase sinking velocity to 16.8 ft/s (5.1 m/s). New hydrostatic pistols increased
9588-439: Was detonated in the vertical column of the Y-gun to propel a depth charge about 45 yd (41 m) over each side of the ship. The main disadvantage of the Y-gun was that it had to be mounted on the centerline of a ship's deck, which could otherwise be occupied by superstructure, masts, or guns. The first were built by New London Ship and Engine Company beginning on 24 November 1917. The K-gun, standardized in 1942, replaced
9690-584: Was fitted in July 1917 and became operational in August. In all, 351 torpedo boat destroyers and 100 other craft were equipped. Projectors called "Y-guns" (in reference to their basic shape), developed by the U.S. Navy's Bureau of Ordnance from the Thornycroft thrower, became available in 1918. Mounted on the centerline of the ship with the arms of the Y pointing outboard, two depth charges were cradled on shuttles inserted into each arm. An explosive propellant charge
9792-722: Was formed in June 1939 in preparation for the naval operations of "Case White", the German invasion of Poland . Called the Reserve Patrol Flotilla, the flotilla consisted of eight commandeered vessels which were gathered together in just three days. By 18 August, orders were placed to increase the flotilla by ten vessels to a total of eighteen. By the end of the Polish campaign in October, a significant number of new Vp-Flotillas had been raised. The 2nd, 3rd, 4th, 8th, and 11th flotillas consisted of eight trawlers each. Eight whalers made up
9894-403: Was initially ineffective in disrupting German convoys. Poorly equipped and coordinated, the British bombers were unable to deal significant damage to convoys between Norway and Germany, partially because of effective protection offered by Vorpostenboote and Sperrbrecher escorts. However, these circumstances would shift in 1941 as Coastal Command received better aircraft, better intelligence, and
9996-427: Was launched from the 21 in (530 mm) torpedo tubes of older destroyers to achieve a sinking velocity of 21 ft/s (6.4 m/s). The launching ship needed to clear the area at 11 knots to avoid damage, and the charge was seldom used. Only 32 were actually fired, and they were known to be troublesome. The teardrop-shaped United States Mark 9 depth charge entered service in the spring of 1943. The charge
10098-539: Was lost. It was a Vorpostenboot , the John Mahn , which was attacked twice by groups of Lockheed Hudson bombers and several fighters, which riddled it with machine gun fire and struck it with two bombs, which ultimately caused the ship to sink. On 28 March 1942, the British Combined Operations Headquarters launched a raid on the port of Saint-Nazaire codenamed Operation Chariot , which had
10200-412: Was to prevent any Soviet vessels from escaping the Baltic. However, there was a strong desire to avoid any major naval engagements, since once the port of Leningrad was taken, Soviet naval resistance would be made impossible. At the outset of the invasion, the Kriegsmarine was mainly occupied with minelaying and minesweeping, and the 3rd Vp-flotilla was part of the large minesweeper contingent patrolling
10302-678: Was unsustainable, as many of the men in the flotillas were being redeployed as infantry and made to fight on the front lines. At the same time as the Normandy landings were taking place, the Soviet Vyborg–Petrozavodsk offensive was initiated to force Finland out of the war. The Soviet Baltic Fleet supported effective amphibious landings which were routing the Finnish defenders. At sea, German mine positions were coming under increasing pressure from Soviet aerial attacks. In July, one mined area
10404-475: Was with aircraft bombs attached to lanyards which triggered them. A similar idea was a 16 lb (7.3 kg) guncotton charge in a lanyarded can. Two of these lashed together became known as the "depth charge Type A". Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the "Type B". These were effective at a distance of around 20 ft (6 m). A 1913 Royal Navy Torpedo School report described
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