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116-516: Depth charges were developed during World War I , and were one of 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

232-645: A blue-water navy was vital for global power projection; Tirpitz had his books translated into German, while Wilhelm made them required reading for his advisors and senior military personnel. However, it was also an emotional decision, driven by Wilhelm's simultaneous admiration for the Royal Navy and desire to surpass it. Bismarck thought that the British would not interfere in Europe, as long as its maritime supremacy remained secure, but his dismissal in 1890 led to

348-592: A grenade at the Archduke's car and injured two of his aides. The other assassins were also unsuccessful. An hour later, as Ferdinand was returning from visiting the injured officers in hospital, his car took a wrong turn into a street where Gavrilo Princip was standing. He fired two pistol shots, fatally wounding Ferdinand and his wife Sophie . According to historian Zbyněk Zeman , in Vienna "the event almost failed to make any impression whatsoever. On 28 and 29 June,

464-540: A guerrilla warfare campaign and only surrendered two weeks after the armistice took effect in Europe. Before the war, Germany had attempted to use Indian nationalism and pan-Islamism to its advantage, a policy continued post-1914 by instigating uprisings in India , while the Niedermayer–Hentig Expedition urged Afghanistan to join the war on the side of Central Powers. However, contrary to British fears of

580-414: 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

696-704: A nuclear warhead is also known as a " nuclear depth bomb ". These were designed to be dropped from 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

812-417: 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

928-408: A change in policy and an Anglo-German naval arms race began. Despite the vast sums spent by Tirpitz, the launch of HMS  Dreadnought in 1906 gave the British a technological advantage. Ultimately, the race diverted huge resources into creating a German navy large enough to antagonise Britain, but not defeat it; in 1911, Chancellor Theobald von Bethmann Hollweg acknowledged defeat, leading to

1044-949: 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

1160-401: 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

1276-613: A direct threat. The 1908–1909 Bosnian Crisis began when Austria annexed the former Ottoman territory of Bosnia and Herzegovina , which it had occupied since 1878. Timed to coincide with the Bulgarian Declaration of Independence from the Ottoman Empire, this unilateral action was denounced by the European powers, but accepted as there was no consensus on how to resolve the situation. Some historians see this as

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1392-471: A gap between the German armies as they closed on Paris. The French army, reinforced by the British expeditionary corps, seized this opportunity to counter-attack and pushed the German army 40 to 80 km back. Both armies were then so exhausted that no decisive move could be implemented, so they settled in trenches, with the vain hope of breaking through as soon as they could build local superiority. In 1911,

1508-432: 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 the target. World War I World War I or

1624-542: 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

1740-467: 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

1856-548: A possibility. This was accentuated by British and Russian support for France against Germany during the 1911 Agadir Crisis . German economic and industrial strength continued to expand rapidly post-1871. Backed by Wilhelm II, Admiral Alfred von Tirpitz sought to use this growth to build an Imperial German Navy , that could compete with the British Royal Navy . This policy was based on the work of US naval author Alfred Thayer Mahan , who argued that possession of

1972-624: 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

2088-834: A revolt in India, the outbreak of the war saw a reduction in nationalist activity. Leaders from the Indian National Congress and other groups believed support for the British war effort would hasten Indian Home Rule , a promise allegedly made explicit in 1917 by Edwin Montagu , the Secretary of State for India . In 1914, the British Indian Army was larger than the British Army itself, and between 1914 and 1918 an estimated 1.3 million Indian soldiers and labourers served in Europe, Africa, and

2204-405: 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 the danger zone before the charges exploded. Depth charges could also be dropped from an aircraft against submarines. At

2320-516: A significant escalation, ending any chance of Austria cooperating with Russia in the Balkans, while also damaging diplomatic relations between Serbia and Italy. Tensions increased after the 1911–1912 Italo-Turkish War demonstrated Ottoman weakness and led to the formation of the Balkan League , an alliance of Serbia, Bulgaria, Montenegro , and Greece . The League quickly overran most of

2436-478: A war on two fronts; the Schlieffen Plan envisaged using 80% of the army to defeat France, then switching to Russia. Since this required them to move quickly, mobilization orders were issued that afternoon. Once the German ultimatum to Russia expired on the morning of 1 August, the two countries were at war. At a meeting on 29 July, the British cabinet had narrowly decided its obligations to Belgium under

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2552-402: A weak Ottoman government, rather than an ambitious Slav power like Bulgaria . Russia had ambitions in northeastern Anatolia while its clients had overlapping claims in the Balkans. These competing interests divided Russian policy-makers and added to regional instability. Austrian statesmen viewed the Balkans as essential for the continued existence of their Empire and saw Serbian expansion as

2668-455: A whole, the Somme offensive led to an estimated 420,000 British casualties, along with 200,000 French and 500,000 Germans. The diseases that emerged in the trenches were a major killer on both sides. The living conditions led to disease and infection, such as trench foot , lice , typhus , trench fever , and the ' Spanish flu '. At the start of the war, German cruisers were scattered across

2784-508: Is known, however, that from 1908 to 1913, military spending by the six major European powers increased by over 50% in real terms. The years before 1914 were marked by a series of crises in the Balkans, as other powers sought to benefit from the Ottoman decline. While Pan-Slavic and Orthodox Russia considered itself the protector of Serbia and other Slav states, they preferred the strategically vital Bosporus straits to be controlled by

2900-439: 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 the ocean floor or surface converge to amplify radial shock waves. Submarines or surface ships may be damaged if operating in

3016-642: Is unlikely to be encountered except in old munitions or unexploded ordnance , although a notable exception to this is the Sting Ray lightweight torpedo, which as of October 2020 remains in service with the Royal Navy and several foreign militaries. The German equivalent of Torpex was Trialen . Torpex was developed at the Royal Gunpowder Factory, Waltham Abbey , in the United Kingdom as a more powerful military alternative to TNT. RDX

3132-574: The Schutzkorps was established, and carried out the persecution of Serbs. The assassination initiated the July Crisis, a month of diplomatic manoeuvring between Austria-Hungary, Germany, Russia, France and Britain. Believing that Serbian intelligence helped organise Franz Ferdinand's murder, Austrian officials wanted to use the opportunity to end their interference in Bosnia and saw war as

3248-641: The World War . In August 1914, the magazine The Independent wrote "This is the Great War. It names itself". In October 1914, the Canadian magazine Maclean's similarly wrote, "Some wars name themselves. This is the Great War." Contemporary Europeans also referred to it as " the war to end war " and it was also described as "the war to end all wars" due to their perception of its unparalleled scale, devastation, and loss of life. The first recorded use of

3364-640: The Australian Naval and Military Expeditionary Force landed on the island of New Britain , then part of German New Guinea . On 28 October, the German cruiser SMS  Emden sank the Russian cruiser Zhemchug in the Battle of Penang . Japan declared war on Germany before seizing territories in the Pacific, which later became the South Seas Mandate , as well as German Treaty ports on

3480-456: 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

3596-538: 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 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

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3712-847: The First World War (28 July 1914 – 11 November 1918), also known as the Great War , was a global conflict between two coalitions: the Allies (or Entente) and the Central Powers . Fighting took place mainly in Europe and the Middle East , as well as in parts of Africa and the Asia-Pacific , and in Europe was characterised by trench warfare ; the widespread use of artillery , machine guns, and chemical weapons (gas); and

3828-668: 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

3944-721: The Rüstungswende or 'armaments turning point', when he switched expenditure from the navy to the army. This decision was not driven by a reduction in political tensions but by German concern over Russia's quick recovery from its defeat in the Russo-Japanese War and subsequent 1905 Russian Revolution . Economic reforms led to a significant post-1908 expansion of railways and transportation infrastructure, particularly in its western border regions. Since Germany and Austria-Hungary relied on faster mobilisation to compensate for their numerical inferiority compared to Russia,

4060-669: 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 the 90SG . China has also produced such weapons. During

4176-766: The United States entered the war on the Allied side following Germany's resumption of unrestricted submarine warfare against Atlantic shipping. Later that year, the Bolsheviks seized power in the Russian October Revolution , and Soviet Russia signed an armistice with the Central Powers in December, followed by a separate peace in March 1918. That month, Germany launched an offensive in

4292-487: The hydrophone and depth charges were introduced, destroyers could potentially successfully attack a submerged submarine. Convoys slowed the flow of supplies since ships had to wait as convoys were assembled; the solution was an extensive program of building new freighters. Troopships were too fast for the submarines and did not travel the North Atlantic in convoys. The U-boats sunk more than 5,000 Allied ships, at

4408-821: The tank . After the First Battle of the Marne in September 1914, Allied and German forces unsuccessfully tried to outflank each other, a series of manoeuvres later known as the " Race to the Sea ". By the end of 1914, the opposing forces confronted each other along an uninterrupted line of entrenched positions from the Channel to the Swiss border. Since the Germans were normally able to choose where to stand, they generally held

4524-588: The 1839 Treaty of London did not require it to oppose a German invasion with military force; however, Prime Minister Asquith and his senior Cabinet ministers were already committed to supporting France, the Royal Navy had been mobilised, and public opinion was strongly in favour of intervention. On 31 July, Britain sent notes to Germany and France, asking them to respect Belgian neutrality; France pledged to do so, but Germany did not reply. Aware of German plans to attack through Belgium, French Commander-in-Chief Joseph Joffre asked his government for permission to cross

4640-563: The 1879 Dual Alliance , which became the Triple Alliance when Italy joined in 1882. For Bismarck, the purpose of these agreements was to isolate France by ensuring the three Empires resolve any disputes between themselves. In 1887, Bismarck set up the Reinsurance Treaty , a secret agreement between Germany and Russia to remain neutral if either were attacked by France or Austria-Hungary. For Bismarck, peace with Russia

4756-441: The 1913 Treaty of London , which had created an independent Albania while enlarging the territories of Bulgaria, Serbia, Montenegro and Greece. However, disputes between the victors sparked the 33-day Second Balkan War , when Bulgaria attacked Serbia and Greece on 16 June 1913; it was defeated, losing most of Macedonia to Serbia and Greece, and Southern Dobruja to Romania. The result was that even countries which benefited from

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4872-569: The Austrians and Serbs clashed at the battles of the Cer and Kolubara ; over the next two weeks, Austrian attacks were repulsed with heavy losses. As a result, Austria had to keep sizeable forces on the Serbian front, weakening their efforts against Russia. Serbia's victory against Austria-Hungary in the 1914 invasion has been called one of the major upset victories of the twentieth century. In 1915,

4988-646: The Austrians briefly occupied the Serbian capital, Belgrade . A Serbian counter-attack in the Battle of Kolubara succeeded in driving them from the country by the end of 1914. For the first 10 months of 1915, Austria-Hungary used most of its military reserves to fight Italy. German and Austro-Hungarian diplomats scored a coup by persuading Bulgaria to join the attack on Serbia. The Austro-Hungarian provinces of Slovenia , Croatia and Bosnia provided troops for Austria-Hungary. Montenegro allied itself with Serbia. Bulgaria declared war on Serbia on 14 October 1915 and joined in

5104-553: The Balkan Wars, such as Serbia and Greece, felt cheated of their "rightful gains", while for Austria it demonstrated the apparent indifference with which other powers viewed their concerns, including Germany. This complex mix of resentment, nationalism and insecurity helps explain why the pre-1914 Balkans became known as the " powder keg of Europe ". On 28 June 1914, Archduke Franz Ferdinand of Austria , heir presumptive to Emperor Franz Joseph I of Austria , visited Sarajevo ,

5220-595: 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

5336-404: The Central Powers. However, the pro-German King Constantine I dismissed the pro-Allied government of Eleftherios Venizelos before the Allied expeditionary force arrived. The Macedonian front was at first mostly static. French and Serbian forces retook limited areas of Macedonia by recapturing Bitola on 19 November 1916 following the costly Monastir offensive , which brought stabilisation of

5452-649: The Chinese Shandong peninsula at Tsingtao . After Vienna refused to withdraw its cruiser SMS  Kaiserin Elisabeth from Tsingtao, Japan declared war on Austria-Hungary, and the ship was sunk in November 1914. Within a few months, Allied forces had seized all German territories in the Pacific, leaving only isolated commerce raiders and a few holdouts in New Guinea. Some of the first clashes of

5568-623: The German High Seas Fleet was confined to port. German U-boats attempted to cut the supply lines between North America and Britain. The nature of submarine warfare meant that attacks often came without warning, giving the crews of the merchant ships little hope of survival. The United States launched a protest, and Germany changed its rules of engagement. After the sinking of the passenger ship RMS Lusitania in 1915, Germany promised not to target passenger liners, while Britain armed its merchant ships, placing them beyond

5684-640: The German Army increased in size from 1908 to 1914, he changed the allocation of forces between the two wings to 70:30. He also considered Dutch neutrality essential for German trade and cancelled the incursion into the Netherlands, which meant any delays in Belgium threatened the viability of the plan. Historian Richard Holmes argues that these changes meant the right wing was not strong enough to achieve decisive success. The initial German advance in

5800-752: The German right wing would sweep through the Netherlands and Belgium , then swing south, encircling Paris and trapping the French army against the Swiss border. The plan's creator, Alfred von Schlieffen , head of the German General Staff from 1891 to 1906, estimated that this would take six weeks, after which the German army would transfer to the East and defeat the Russians. The plan was substantially modified by his successor, Helmuth von Moltke

5916-426: The Germans bled heavily as well, with anywhere from 700,000 to 975,000 casualties between the two combatants. Verdun became a symbol of French determination and self-sacrifice. The Battle of the Somme was an Anglo-French offensive from July to November 1916. The opening day on 1 July 1916 was the bloodiest single day in the history of the British Army , which suffered 57,500 casualties, including 19,200 dead. As

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6032-435: The Japanese. In April 1942, 100 tons of Composition C (88% RDX and oil desensitizer), also known as C4 , was ordered by the Office of Strategic Services. By 8 May 1945 ( Victory in Europe Day ) the Holston Ordnance Works had been in full production of RDX with no end in sight. In July of that year government officials informed the plant to not exceed production quotas (as had been the practice to that point) since they knew that

6148-565: The Middle East. In all, 140,000 soldiers served on the Western Front and nearly 700,000 in the Middle East, with 47,746 killed and 65,126 wounded. The suffering engendered by the war, as well as the failure of the British government to grant self-government to India afterward, bred disillusionment, resulting in the campaign for full independence led by Mahatma Gandhi . Pre-war military tactics that had emphasised open warfare and individual riflemen proved obsolete when confronted with conditions prevailing in 1914. Technological advances allowed

6264-703: The Ottoman Empire , which disturbed the long-standing balance of power in Europe, as well as economic competition between nations triggered by industrialisation and imperialism . Growing tensions between the great powers and in the Balkans reached a breaking point on 28 June 1914, when a Bosnian Serb named Gavrilo Princip assassinated Archduke Franz Ferdinand , heir to the Austro-Hungarian throne. Austria-Hungary held Serbia responsible, and declared war on 28 July. After Russia mobilised in Serbia's defence, Germany declared war on Russia and France , who had an alliance . The United Kingdom entered after Germany invaded Belgium , whose neutrality it guaranteed, and

6380-545: The Ottomans joined the Central Powers in November. Germany's strategy in 1914 was to quickly defeat France, then to transfer its forces to the east, but its advance was halted in September , and by the end of the year the Western Front consisted of a continuous line of trenches stretching from the English Channel to Switzerland. The Eastern Front was more dynamic, but neither side gained a decisive advantage, despite costly offensives. Italy , Bulgaria , Romania , Greece and others joined in from 1915 onward. In April 1917,

6496-449: The Ottomans' territory in the Balkans during the 1912–1913 First Balkan War , much to the surprise of outside observers. The Serbian capture of ports on the Adriatic resulted in partial Austrian mobilisation, starting on 21 November 1912, including units along the Russian border in Galicia . The Russian government decided not to mobilise in response, unprepared to precipitate a war. The Great Powers sought to re-assert control through

6612-438: 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

6728-549: The Russian Stavka agreed with the French to attack Germany within fifteen days of mobilisation, ten days before the Germans had anticipated, although it meant the two Russian armies that entered East Prussia on 17 August did so without many of their support elements. By the end of 1914, German troops held strong defensive positions inside France, controlled the bulk of France's domestic coalfields, and inflicted 230,000 more casualties than it lost itself. However, communications problems and questionable command decisions cost Germany

6844-429: The Serbian retreat toward the Adriatic coast in the Battle of Mojkovac on 6–7 January 1916, but ultimately the Austrians also conquered Montenegro. The surviving Serbian soldiers were evacuated to Greece. After the conquest, Serbia was divided between Austro-Hungary and Bulgaria. In late 1915, a Franco-British force landed at Salonica in Greece to offer assistance and to pressure its government to declare war against

6960-442: 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

7076-429: 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 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

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7192-455: The West was very successful. By the end of August, the Allied left, which included the British Expeditionary Force (BEF), was in full retreat , and the French offensive in Alsace-Lorraine was a disastrous failure, with casualties exceeding 260,000. German planning provided broad strategic instructions while allowing army commanders considerable freedom in carrying them out at the front, but von Kluck used this freedom to disobey orders, opening

7308-414: 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 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

7424-430: The Younger . Under Schlieffen, 85% of German forces in the west were assigned to the right wing, with the remainder holding along the frontier. By keeping his left-wing deliberately weak, he hoped to lure the French into an offensive into the "lost provinces" of Alsace-Lorraine , which was the strategy envisaged by their Plan XVII . However, Moltke grew concerned that the French might push too hard on his left flank and as

7540-446: The aggressor, German Chancellor Bethmann Hollweg delayed the commencement of war preparations until 31 July. That afternoon, the Russian government were handed a note requiring them to "cease all war measures against Germany and Austria-Hungary" within 12 hours. A further German demand for neutrality was refused by the French who ordered general mobilization but delayed declaring war. The German General Staff had long assumed they faced

7656-399: 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

7772-418: The aluminium component made the explosive pulse last longer, which increased the destructive power. Besides torpedoes, naval mines , and depth charges , Torpex was only used in the Upkeep , Tallboy and Grand Slam bombs as well as the drones employed in Operation Aphrodite . Torpex has long been superseded by H6 and Polymer-bonded explosive (PBX) compositions. It is regarded as obsolete and Torpex

7888-407: The attack by the Austro-Hungarian army under Mackensen's army of 250,000 that was already underway. Serbia was conquered in a little more than a month, as the Central Powers, now including Bulgaria, sent in 600,000 troops in total. The Serbian army, fighting on two fronts and facing certain defeat, retreated into northern Albania . The Serbs suffered defeat in the Battle of Kosovo . Montenegro covered

8004-477: The best way of achieving this. However, the Foreign Ministry had no solid proof of Serbian involvement. On 23   July, Austria delivered an ultimatum to Serbia, listing ten demands made intentionally unacceptable to provide an excuse for starting hostilities. Serbia ordered general mobilization on 25   July, but accepted all the terms, except for those empowering Austrian representatives to suppress "subversive elements" inside Serbia, and take part in

8120-483: The border and pre-empt such a move. To avoid violating Belgian neutrality, he was told any advance could come only after a German invasion. Instead, the French cabinet ordered its Army to withdraw 10 km behind the German frontier, to avoid provoking war. On 2 August, Germany occupied Luxembourg and exchanged fire with French units when German patrols entered French territory; on 3   August, they declared war on France and demanded free passage across Belgium, which

8236-427: The campaign saw the first use of anti-aircraft warfare after an Austrian plane was shot down with ground-to-air fire, as well as the first medical evacuation by the Serbian army. Upon mobilisation, in accordance with the Schlieffen Plan , 80% of the German Army was located on the Western Front, with the remainder acting as a screening force in the East. Rather than a direct attack across their shared frontier,

8352-649: The capital of the recently annexed Bosnia and Herzegovina . Cvjetko Popović , Gavrilo Princip , Nedeljko Čabrinović , Trifko Grabež , Vaso Čubrilović ( Bosnian Serbs ) and Muhamed Mehmedbašić (from the Bosniaks community), from the movement known as Young Bosnia , took up positions along the Archduke's motorcade route, to assassinate him. Supplied with arms by extremists within the Serbian Black Hand intelligence organisation, they hoped his death would free Bosnia from Austrian rule. Čabrinović threw

8468-466: The chance of a decisive outcome, while it had failed to achieve the primary objective of avoiding a long, two-front war. As was apparent to several German leaders, this amounted to a strategic defeat; shortly after the First Battle of the Marne , Crown Prince Wilhelm told an American reporter "We have lost the war. It will go on for a long time but lost it is already." On 30 August 1914, New Zealand occupied German Samoa (now Samoa ). On 11 September,

8584-424: 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 the submarine if detonated close enough. The secondary shock wave is a result of the cyclical expansion and contraction of

8700-520: The cost of 199 submarines. World War I also saw the first use of aircraft carriers in combat, with HMS  Furious launching Sopwith Camels in a successful raid against the Zeppelin hangars at Tondern in July 1918, as well as blimps for antisubmarine patrol. Faced with Russia in the east, Austria-Hungary could spare only one-third of its army to attack Serbia. After suffering heavy losses,

8816-522: The creation of new independent states, including Poland , Finland , the Baltic states , Czechoslovakia , and Yugoslavia . The League of Nations was established to maintain world peace, but its failure to manage instability during the interwar period contributed to the outbreak of World War II in 1939. Before World War II , the events of 1914–1918 were generally known as the Great War or simply

8932-449: The creation of strong defensive systems largely impervious to massed infantry advances, such as barbed wire , machine guns and above all far more powerful artillery , which dominated the battlefield and made crossing open ground extremely difficult. Both sides struggled to develop tactics for breaching entrenched positions without heavy casualties. In time, technology enabled the production of new offensive weapons, such as gas warfare and

9048-965: The crowds listened to music and drank wine, as if nothing had happened." Nevertheless, the impact of the murder of the heir to the throne was significant, and has been described by historian Christopher Clark as a "9/11 effect, a terrorist event charged with historic meaning, transforming the political chemistry in Vienna". Austro-Hungarian authorities encouraged subsequent anti-Serb riots in Sarajevo . Violent actions against ethnic Serbs were also organised outside Sarajevo, in other cities in Austro-Hungarian-controlled Bosnia and Herzegovina, Croatia and Slovenia. Austro-Hungarian authorities in Bosnia and Herzegovina imprisoned approximately 5,500 prominent Serbs, 700 to 2,200 of whom died in prison. A further 460 Serbs were sentenced to death. A predominantly Bosniak special militia known as

9164-561: 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 a wider dispersal pattern when used in conjunction with rack-deployed charges. The first of these

9280-695: The expansion of the French colonial empire . In 1873, Bismarck negotiated the League of the Three Emperors , which included Austria-Hungary , Russia and Germany. After the 1877–1878 Russo-Turkish War , the League was dissolved due to Austrian concerns over the expansion of Russian influence in the Balkans , an area they considered to be of vital strategic interest. Germany and Austria-Hungary then formed

9396-456: The expansion time of the explosive product gases. Beeswax was also added as a phlegmatizing agent, to reduce sensitivity to shock and impact. Later, beeswax was replaced with paraffin wax , and calcium chloride was added as a moisture absorber to reduce the production of hydrogen gas under high humidity. The production of RDX in the USA skyrocketed following the attack on Pearl Harbor by

9512-404: 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 a killing radius (resulting in

9628-463: The first time on the Western Front. Several types of gas soon became widely used by both sides and though it never proved a decisive, battle-winning weapon, it became one of the most feared and best-remembered horrors of the war. In February 1916, the Germans attacked French defensive positions at the Battle of Verdun , lasting until December 1916. Casualties were greater for the French, but

9744-595: The front. Serbian and French troops finally made a breakthrough in September 1918 in the Vardar offensive , after most German and Austro-Hungarian troops had been withdrawn. The Bulgarians were defeated at the Battle of Dobro Pole , and by 25 September British and French troops had crossed the border into Bulgaria proper as the Bulgarian army collapsed. Bulgaria capitulated four days later, on 29 September 1918. The German high command responded by despatching troops to hold

9860-411: 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 the secondary shock wave can be reinforced if another depth charge detonates on the other side of the hull in close time proximity to

9976-508: 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 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

10092-542: The globe, some of which were subsequently used to attack Allied merchant shipping . These were systematically hunted down by the Royal Navy, though not before causing considerable damage. One of the most successful was the SMS ; Emden , part of the German East Asia Squadron stationed at Qingdao , which seized or sank 15 merchantmen, a Russian cruiser and a French destroyer. Most of the squadron

10208-549: The high ground, while their trenches tended to be better built; those constructed by the French and English were initially considered "temporary", only needed until an offensive would destroy the German defences. Both sides tried to break the stalemate using scientific and technological advances. On 22 April 1915, at the Second Battle of Ypres , the Germans (violating the Hague Convention ) used chlorine gas for

10324-435: The introductions of tanks and aircraft . World War I was one of the deadliest conflicts in history , resulting in an estimated 10 million military dead and more than 20 million wounded , plus some 10 million civilian dead from causes including genocide . The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic. The causes of World War I included the rise of Germany and decline of

10440-470: The investigation and trial of Serbians linked to the assassination. Claiming this amounted to rejection, Austria broke off diplomatic relations and ordered partial mobilisation the next day; on 28 July, they declared war on Serbia and began shelling Belgrade . Russia ordered general mobilization in support of Serbia on 30 July. Anxious to ensure backing from the SPD political opposition by presenting Russia as

10556-544: 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

10672-566: The line, but these forces were too weak to re-establish a front. Torpex Torpex ("Torpedo explosive") is a secondary explosive , 50% more powerful than TNT by mass. Torpex comprises 42% RDX , 40% TNT and 18% powdered aluminium . It was used in the Second World War from late 1942, at which time some used the names Torpex and RDX interchangeably, much to the confusion of today's historical researchers. Torpex proved to be particularly useful in underwater munitions because

10788-532: 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

10904-465: The ocean, even to neutral ships. Since there was limited response to this tactic, Germany expected a similar response to its unrestricted submarine warfare. The Battle of Jutland in May/June 1916 was the only full-scale clash of battleships during the war, and one of the largest in history. The clash was indecisive, though the Germans inflicted more damage than they received; thereafter the bulk of

11020-801: The protection of the " cruiser rules ", which demanded warning and movement of crews to "a place of safety" (a standard that lifeboats did not meet). Finally, in early 1917, Germany adopted a policy of unrestricted submarine warfare , realising the Americans would eventually enter the war. Germany sought to strangle Allied sea lanes before the United States could transport a large army overseas, but, after initial successes, eventually failed to do so. The U-boat threat lessened in 1917, when merchant ships began travelling in convoys , escorted by destroyers . This tactic made it difficult for U-boats to find targets, which significantly lessened losses; after

11136-563: 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

11252-528: 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 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

11368-595: 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

11484-413: 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 the surrounding water. Surrounding water pressure then collapses the gas bubble with inward momentum causing excess pressure within

11600-408: 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

11716-469: The term First World War was in September 1914 by German biologist and philosopher Ernst Haeckel who stated, "There is no doubt that the course and character of the feared 'European War' ... will become the first world war in the full sense of the word." For much of the 19th century, the major European powers maintained a tenuous balance of power , known as the Concert of Europe . After 1848, this

11832-691: The threat posed by the closing of this gap was more important than competing with the Royal Navy. After Germany expanded its standing army by 170,000 troops in 1913, France extended compulsory military service from two to three years; similar measures were taken by the Balkan powers and Italy, which led to increased expenditure by the Ottomans and Austria-Hungary. Absolute figures are difficult to calculate due to differences in categorising expenditure since they often omit civilian infrastructure projects like railways which had logistical importance and military use. It

11948-404: 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 the pressure of the surrounding water. This gas expansion propagates a shock wave. The density difference of the expanding gas bubble from

12064-645: The war ended with the Armistice of 11 November 1918 . The Paris Peace Conference of 1919–1920 imposed settlements on the defeated powers, most notably the Treaty of Versailles , by which Germany lost significant territories, was disarmed, and was required to pay large war reparations to the Allies. The dissolution of the Russian, German, Austro-Hungarian, and Ottoman Empires redrew national boundaries and resulted in

12180-601: The war involved British, French, and German colonial forces in Africa. On 6–7 August, French and British troops invaded the German protectorates of Togoland and Kamerun . On 10 August, German forces in South-West Africa attacked South Africa; sporadic and fierce fighting continued for the rest of the war. The German colonial forces in German East Africa , led by Colonel Paul von Lettow-Vorbeck , fought

12296-477: The west , which despite initial successes left the German Army exhausted and demoralised. A successful Allied counter-offensive from August 1918 caused a collapse of the German front line. By early November, Bulgaria, the Ottoman Empire and Austria-Hungary had each signed armistices with the Allies, leaving Germany isolated. Facing a revolution at home , Kaiser Wilhelm   II abdicated on 9 November, and

12412-525: 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

12528-403: Was challenged by Britain's withdrawal into so-called splendid isolation , the decline of the Ottoman Empire , New Imperialism , and the rise of Prussia under Otto von Bismarck . Victory in the 1870–1871 Franco-Prussian War allowed Bismarck to consolidate a German Empire . Post-1871, the primary aim of French policy was to avenge this defeat, but by the early 1890s, this had switched to

12644-510: 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

12760-542: 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 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

12876-471: Was developed in 1899. Though very stable and serving as the reference point by which the sensitivity of other explosives are judged, it was too expensive for most military applications and reserved for use in the most important products, such as torpedoes. Aluminium powder was also added to the mix to further enhance the effect. Although both RDX and TNT have a negative oxygen balance , the superheated aluminium component tends to contribute primarily by extending

12992-423: 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

13108-654: Was refused. Early on the morning of 4   August, the Germans invaded, and Albert I of Belgium called for assistance under the Treaty of London . Britain sent Germany an ultimatum demanding they withdraw from Belgium; when this expired at midnight, without a response, the two empires were at war. Germany promised to support Austria-Hungary's invasion of Serbia, but interpretations of what this meant differed. Previously tested deployment plans had been replaced early in 1914, but those had never been tested in exercises. Austro-Hungarian leaders believed Germany would cover its northern flank against Russia. Beginning on 12 August,

13224-667: Was returning to Germany when it sank two British armoured cruisers at the Battle of Coronel in November 1914, before being virtually destroyed at the Battle of the Falkland Islands in December. The SMS Dresden escaped with a few auxiliaries, but after the Battle of Más a Tierra , these too were either destroyed or interned. Soon after the outbreak of hostilities, Britain began a naval blockade of Germany . This proved effective in cutting off vital supplies, though it violated accepted international law. Britain also mined international waters which closed off entire sections of

13340-781: Was the foundation of German foreign policy but in 1890, he was forced to retire by Wilhelm II . The latter was persuaded not to renew the Reinsurance Treaty by his new Chancellor , Leo von Caprivi . This gave France an opening to agree the Franco-Russian Alliance in 1894, which was then followed by the 1904 Entente Cordiale with Britain. The Triple Entente was completed by the 1907 Anglo-Russian Convention . While not formal alliances, by settling long-standing colonial disputes in Asia and Africa, British support for France or Russia in any future conflict became

13456-472: 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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