Atlantic U-boat Campaign (World War I)
The Atlantic U-boat Campaign of World War I was the naval
Naval warfare
Naval warfare is combat in and on seas, oceans, or any other major bodies of water such as large lakes and wide rivers.-History:Mankind has fought battles on the sea for more than 3,000 years. Land warfare would seem, initially, to be irrelevant and entirely removed from warfare on the open ocean,...

 campaign fought by German U-boat
U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

s in Atlantic waters, that is, the seas around the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...

, the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

, and the coast of France. Initially directed against the British Grand Fleet, later it was extended to include action against the trade routes of the Entente Powers. The campaign was highly destructive, and resulted in the loss of nearly half of Britain's merchant marine fleet during the course of the war.

First patrols

On 6 August 1914, two days after Britain had declared war on Germany, the German U-boats U-5, U-7
SM U-7 (Germany)
SM U-7 was one of the 329 submarines serving in the Imperial German Navy in World War I.U-7 was engaged in the naval warfare and took part in the First Battle of the Atlantic.- Original documents from Room 40 :...

, U-8
SM U-8
SM U-8 was one of the 329 submarines serving in the Imperial German Navy in World War I.U-8 was engaged in the naval warfare and took part in the First Battle of the Atlantic....

, U-9, U-13
SM U-13
SM U-13 was one of the 329 submarines serving in the Imperial German Navy in World War I. U-13 was engaged in the naval warfare and took part in the First Battle of the Atlantic.-External link:*...

, U-14
SM U-14 (Germany)
SM U-14 was one of the 329 submarines serving in the Imperial German Navy in World War I.U-14 was engaged in the naval warfare and took part in the First Battle of the Atlantic....

, U-15, U-16
SM U-16 (Germany)
SM U-16 was one of the 329 submarines serving in the Imperial German Navy in World War I.U-16 was engaged in the naval warfare and took part in the First Battle of the Atlantic....

, U-17, and U-18
SM U-18
SM U-18 was one of 329 submarines serving in the Imperial German Navy in World War I. U-18 engaged in the commerce warfare in the First Battle of the Atlantic.Launched in October 1914, she was commanded by Kaptlt...

 sailed from their base in Heligoland
Heligoland is a small German archipelago in the North Sea.Formerly Danish and British possessions, the islands are located in the Heligoland Bight in the south-eastern corner of the North Sea...

 to attack Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 warships in the North Sea in the first submarine war patrols in history.

The U-boats sailed north, hoping to encounter Royal Navy squadrons between Shetland and Bergen
Bergen is the second largest city in Norway with a population of as of , . Bergen is the administrative centre of Hordaland county. Greater Bergen or Bergen Metropolitan Area as defined by Statistics Norway, has a population of as of , ....

. On 8 August, one of U-9's engines broke down and she was forced to return to base. On the same day, off Fair Isle
Fair Isle
Fair Isle is an island in northern Scotland, lying around halfway between mainland Shetland and the Orkney islands. It is famous for its bird observatory and a traditional style of knitting.-Geography:...

, U-15 sighted the British battleships HMS Ajax
HMS Ajax (1912)
HMS Ajax was a King George V-class battleship , built at Scotts' shipyard at Greenock on the River Clyde...

, Monarch
HMS Monarch (1911)
HMS Monarch was an Orion-class battleship of the Royal Navy. She served in the 2nd Battle Squadron of the Grand Fleet in World War I, and fought at the Battle of Jutland, 31 May 1916, suffering no damage....

, and Orion
HMS Orion (1910)
HMS Orion was a dreadnought battleship of the Royal Navy. Launched in 1910, she was the lead ship of her class; she was the first so-called "super-dreadnought", being the first British dreadnought to mount guns of calibre greater than twelve inches, and the first British dreadnought to have...

 on manoeuvres and fired a torpedo at Monarch. This failed to hit, and succeeded only in putting the battleships on their guard. At dawn the next morning, the 1st Light Cruiser Squadron, which was screening the battleships, came into contact with the U-boats, HMS Birmingham
HMS Birmingham (1913)
HMS Birmingham was lead ship of the Birmingham group of three ships of the "Town" class of light cruisers built by the Royal Navy. Her sister ships were and...

 sighting U-15, which was lying on the surface. There was no sign of any lookouts on the U-boat and sounds of hammering could be heard, as though her crew were performing repairs. Birmingham immediately altered course and rammed U-15 just behind her conning tower. The submarine was cut in two and sank with all hands.

On 12 August, seven U-boats returned to Heligoland; U-13 was also missing, and it was thought she had been mined
Naval mine
A naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...

. While the operation was a failure, it caused the Royal Navy some uneasiness, disproving earlier estimates as to U-boats' radius of action and leaving the security of the Grand Fleet's unprotected anchorage at Scapa Flow
Scapa Flow
right|thumb|Scapa Flow viewed from its eastern endScapa Flow is a body of water in the Orkney Islands, Scotland, United Kingdom, sheltered by the islands of Mainland, Graemsay, Burray, South Ronaldsay and Hoy. It is about...

 open to question. On the other hand, the ease with which U-15 had been destroyed by Birmingham encouraged the false belief submarines were no great danger to surface warships.

First successes

On 5 September 1914, U-21
SM U-21 (Germany)
SM U-21 was one of the most famous U-boats to serve in the Imperial German Navy in World War I. She was the first submarine to sink a ship with a self-propelled torpedo. She also sank the British battleships HMS Triumph and HMS Majestic...

 commanded by Lieutenant Otto Hersing made history when he torpedoed the Royal Navy light cruiser HMS Pathfinder
HMS Pathfinder (1904)
HMS Pathfinder was the lead ship of the Pathfinder class scout cruisers, and was the first ship ever to be sunk by a torpedo fired by submarine . She was built by Cammell Laird, Birkenhead, launched on 16 July 1904, and commissioned on 18 July 1905...

. The cruiser's magazine
Magazine (artillery)
Magazine is the name for an item or place within which ammunition is stored. It is taken from the Arabic word "makahazin" meaning "warehouse".-Ammunition storage areas:...

 exploded, and the ship sank in four minutes, taking 259 of her crew with her. It was the first combat victory of the modern submarine.

The German U-boats were to get even luckier on 22 September. Early in the morning of that day, a lookout on the bridge of U-9, commanded by Lieutenant Otto Weddigen
Otto Weddigen
Otto Eduard Weddigen was a German U-boat commander during World War I.-Biography and career:He was born in Herford and started his military career in the Kaiserliche Marine in 1901...

, spotted a vessel on the horizon. Weddigen ordered the U-boat to submerge immediately, and the submarine went forward to investigate.

At closer range, Weddigen discovered three old Royal Navy armoured cruisers, Aboukir
HMS Aboukir (1900)
HMS Aboukir was a Cressy-class armoured cruiser. She was built by Fairfield Shipbuilding & Engineering Co Ltd, Govan, Scotland in 1902.-First World War:...

, Cressy
HMS Cressy (1899)
HMS Cressy was a Cressy-class armoured cruiser in the Royal Navy. Cressy was sunk by the German U-boat U-9 in September 1914.-Service history:...

, and Hogue
HMS Hogue (1900)
HMS Hogue was a Cressy-class armoured cruiser in the Royal Navy. Hogue was sunk by the German U-boat U-9 on 22 September 1914.-Service history:...

. These three vessels were not merely antiquated, but were staffed mostly by reservists, and were so clearly vulnerable that a decision to withdraw them was already filtering up through the bureaucracy of the Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...

. The order did not come soon enough for the ships. Weddigen sent one torpedo into Aboukir. The captains of Hogue and Cressy assumed Aboukir had struck a mine and came up to assist. U 9 put two torpedoes into Hogue, and then hit Cressy with two more torpedoes as the cruiser tried to flee. The three cruisers sank in less than an hour, killing 1,460 British sailors.

Three weeks later, on 15 October, Weddigen also sank the old cruiser Hawke
HMS Hawke (1891)
HMS Hawke, launched in 1891, was the sixth British warship to be named Hawke. She was an Edgar-class protected cruiser.-Service:...

, and the crew of U 9 became national heroes. Each was awarded the Iron Cross
Iron Cross
The Iron Cross is a cross symbol typically in black with a white or silver outline that originated after 1219 when the Kingdom of Jerusalem granted the Teutonic Order the right to combine the Teutonic Black Cross placed above a silver Cross of Jerusalem....

 Second Class, except for Weddigen, who received the Iron Cross First Class. The sinkings caused alarm within the British Admiralty, which was increasingly nervous about the security of the Scapa Flow anchorage, and the fleet was sent to ports in Ireland and the west coast of Scotland until adequate defenses were installed at Scapa Flow. This, in a sense, was a more significant victory than sinking a few old cruisers; the world's most powerful fleet had been forced to abandon its home base.

End of the first campaign

These concerns were well-founded. On 23 November U-18
SM U-18
SM U-18 was one of 329 submarines serving in the Imperial German Navy in World War I. U-18 engaged in the commerce warfare in the First Battle of the Atlantic.Launched in October 1914, she was commanded by Kaptlt...

 penetrated Scapa Flow via Hoxa Sound, following a steamer through the boom and entering the anchorage with little difficulty. However, the fleet was absent, being dispersed in achorages on the west coast of Scotland and Ireland. As U-18 was making her way back out to the open sea, her periscope was spotted by a guard boat. The trawler Dorothy Gray altered course and rammed the periscope, rendering it unserviceable. U-18 then suffered a failure of her diving plane motor and the boat became unable to maintain her depth, at one point even impacting the seabed. Eventually, her captain was forced to surface and scuttle his command, and all but one crewmember were picked up by British boats.

The last success of the year came on 31 December. U-24
SM U-24
SM U-24 was one of 329 submarines serving in the Imperial German Navy in World War I. She was engaged in commerce warfare during the First Battle of the Atlantic....

 sighted the British battle ship Formidable
HMS Formidable (1898)
HMS Formidable —the third of four ships of that name to serve in the Royal Navy—was the lead ship of her class of pre-dreadnought battleships. She was the second British battleship to be sunk by enemy action during the First World War...

 on manoeuvres in the Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...

 and torpedoed her. Formidable sank with the loss of 547 of her crew. The C-in-C Channel Fleet, Adm. Sir Lewis Bayly
Lewis Bayly (Royal Navy officer)
Sir Lewis Bayly , KCB, KCMG, CVO, was a British admiral during the First World War.-Early life:Bayly was born at Woolwich on 28 September 1857. He was a greatgreatnephew of Admiral Keats. Bayly joined the Royal Navy in 1870. He served in the Third Anglo-Ashanti War and against pirates in the Congo...

, was criticized for not taking proper precautions during the exercises, but was cleared of the charge of negligence. Bayly later served with distinction as commander of the anti-submarine warfare forces at Queenstown.

First attacks on merchant ships

The first attacks on merchant ships had started in October 1914. On 20 October SS Glitra
SS Glitra
SS Glitra was a steam ship that was the first British merchant vessel to be sunk by a German submarine in the First World War.-History:...

 became the first British merchant vessel to be sunk by a German submarine in World War I. Glitra, bound from Grangemouth
Grangemouth is a town and former burgh in the council area of Falkirk, Scotland. The town lies in the Forth Valley, on the banks of the Firth of Forth, east of Falkirk, west of Bo'ness and south-east of Stirling. Grangemouth had a resident population of 17,906 according to the 2001...

 to Stavanger
Stavanger is a city and municipality in the county of Rogaland, Norway.Stavanger municipality has a population of 126,469. There are 197,852 people living in the Stavanger conurbation, making Stavanger the fourth largest city, but the third largest urban area, in Norway...

, Norway, was stopped and searched by U-17, under the command of Kapitänleutnant Johannes Feldkirchener. The operation was performed broadly in accordance with the "cruiser rules", the crew being ordered into the lifeboats before Glitra was sunk by having her seacock
A seacock is a valve on the hull of a boat, permitting water to flow into the boat, such as for cooling an engine or for a salt water faucet; or out of the boat, such as for a sink drain or a toilet....

s opened. It was the first time in history a submarine sank a merchant ship.

Less than a week later, on 26 October, U-24 became the first submarine to attack an unarmed merchant ship without warning, when she torpedoed the steamship Admiral Ganteaume, with 2,500 Belgian refugees aboard. Although the ship did not sink, and was towed into Boulogne, 40 lives were lost, mainly due to panic. The U-boat's commander, Rudolf Schneider, claimed he had mistaken her for a troop transport.

On 30 January 1915, U-20, commanded by Kapitänleutnant Otto Dröscher, torpedoed and sank the steamers Ikaria, Tokomaru, and Oriole without warning, and on 1 February fired a torpedo at, but missed, the hospital ship
Hospital ship
A hospital ship is a ship designated for primary function as a floating medical treatment facility or hospital; most are operated by the military forces of various countries, as they are intended to be used in or near war zones....

 Asturias, despite her being clearly identifiable as a hospital ship by her white paintwork with green bands and red crosses.

Unrestricted submarine warfare

In February 1915 the first unrestricted campaign against Allied trade was started. The U-boat had several deficiencies for a commerce raider; its low speed, even on the surface, made it scarcely faster than many merchant ships, while its light gun armament was inadequate against larger vessels. To use the U-boat's chief weapon, the attack without warning, using torpedoes, meant abandoning the stop-and-search required to avoid harming neutrals.

In the first month 29 ships totalling 89,517 gross register tons (GRT) were sunk, a pace of destruction which was maintained throughout the summer. As the sinkings increased, so too did the number of politically damaging incidents. On 19 February U-8 torpedoed Belridge, a neutral
Neutral country
A neutral power in a particular war is a sovereign state which declares itself to be neutral towards the belligerents. A non-belligerent state does not need to be neutral. The rights and duties of a neutral power are defined in Sections 5 and 13 of the Hague Convention of 1907...

 tanker travelling between two neutral ports; in March U-boats sank Hanna and Medea, a Swedish and a Dutch freighter; in April two Greek vessels.

In March also, Falaba was sunk, with the loss of one American life, and in April Harpalyce, a Belgian Relief
Committee for Relief in Belgium
The Commission for Relief in Belgium or C.R.B. − known also as just Belgian Relief − was an international organization that arranged for the supply of food to German-occupied Belgium and northern France during the First World War.Its leading figure was chairman Herbert Hoover .- Origins :When the...

 ship, was sunk. On 7 May, U-20 sank Lusitania
RMS Lusitania
RMS Lusitania was a British ocean liner designed by Leonard Peskett and built by John Brown and Company of Clydebank, Scotland. The ship entered passenger service with the Cunard Line on 26 August 1907 and continued on the line's heavily-traveled passenger service between Liverpool, England and New...

 with the loss of 1,198 lives, 128 of them American citizens.

British countermeasures were largely ineffective. The most effective defensive measures proved to be advising merchantment to turn towards the U-boat and attempt to ram, forcing it to submerge. Over half of all attacks on merchant ships by U-boats were defeated in this way. This response freed the U-boat to attack without warning, however. In March 1915, this tactic was used by the packet  to escape an attack by U-33
SM U-33
SM U-33 was a German Type U 31 U-boat of the Kaiserliche Marine.-SS Brussels:On 28 March 1916, U-33 ordered the Great Eastern Railway's to stop...

. For this her captain, Charles Fryatt
Charles Fryatt
Charles Algernon Fryatt was a British mariner who attempted to ram a German U-boat in 1915. His ship, the was captured by the Germans in 1916. When it became clear who he was, Fryatt was court-martialled and executed, although he was a civilian. There was international outrage following his...

, was executed after being captured by the Germans in June 1916.

Another option was arming ships for self defence, which, according to the Germans, put them outside the protection of the cruiser rules.

Another option was to arm and man decoy ships with hidden guns, the so-called Q-ship
Q-ships, also known as Q-boats, Decoy Vessels, Special Service Ships, or Mystery Ships, were heavily armed merchant ships with concealed weaponry, designed to lure submarines into making surface attacks. This gave Q-ships the chance to open fire and sink them...

. A variant on the idea was to equip small vessels with a submarine escort. In 1915, three U-boats were sunk by Q-ships, and two more by submarines accompanying trawlers. In June also U-40 was sunk by C-24
HMS C24 was a British C class submarine built by Vickers, Barrow. She was laid down on 12 February 1908 and was commissioned on 5 May 1909.-Service history:...

 while attacking Taranaki, and in July U-23 was sunk by C-27 attacking Princess Louise. Also in July U-36 was sunk by the Q-ship Prince Charles, and in August and September U-27 and U-41 were sunk by Baralong, the former in the notorious Baralong Incident
Baralong Incident
The Baralong Incidents were naval engagements of the First World War in August and September 1915, involving the Royal Navy Q-Ship HMS Baralong, later renamed HMS Wyandra, and two German U-boats....


There were, however, no means to detect submerged U-boats, and attacks on them were limited to efforts to damage their periscopes with hammers dropping 18.5 lb (8.4 kg) hand-thrown guncotton bombs. Use of nets to ensnare U-boats was also examined, as was a destroyer, Starfish
HMS Starfish
Three ships of the Royal Navy have borne the name HMS Starfish, after the Starfish, a marine creature:*HMS Starfish was an A class destroyer of the Sturgeon subgroup. She was launched in 1894 and sold in 1911....

, fitted with a spar torpedo
Spar torpedo
A spar torpedo is a weapon consisting of a bomb placed at the end of a long pole, or spar, and attached to a boat. The weapon is used by running the end of the spar into the enemy ship. Spar torpedoes were often equipped with a barbed spear at the end, so it would stick to wooden hulls...


In all, 16 U-boats were destroyed during this phase of the campaign, while they themselves sank 370 ships totalling 750,000 grt.

1916: in support of the High Seas fleet

In 1916 the German Navy returned to a strategy of using the U-boats to erode the Grand Fleet's numerical superiority by staging a series of operations designed to lure the Grand Fleet into a U-boat trap. Because of the U-boats' poor speed compared to the main battle fleet these operations required U-boat patrol lines to be set up, while the High Seas fleet manoeuvred to draw the Grand Fleet to them.

Several of these operations were staged, in March and April 1916, but with no success. Ironically, the major fleet action which did take place, the Battle of Jutland
Battle of Jutland
The Battle of Jutland was a naval battle between the British Royal Navy's Grand Fleet and the Imperial German Navy's High Seas Fleet during the First World War. The battle was fought on 31 May and 1 June 1916 in the North Sea near Jutland, Denmark. It was the largest naval battle and the only...

, in May 1916, saw no U-boat involvement at all; the fleets met and engaged largely by chance, and there were no U-boat patrols anywhere near the battle area. A further series of operations, in August and October 1916, were similarly unfruitful, and the strategy was abandoned in favour of resuming commerce warfare.

1917: renewed "unrestricted" campaign

In 1917 Germany decided to resume full unrestricted submarine warfare. It was expected to bring America into the war, but the Germans gambled that they could defeat Britain by this means before the US could mobilize. German planners estimated that if the sinked tonnage exceeds 600,000 tons per month, Britain would be forced to sue for peace after 5 to 6 months.

In February 1917 U-boats sank over 414,000 GRT in the war zone around Britain, 80% of the total for the month; in March they sank over 500, 000 (90%), in April over 600,000 of 860,000 GRT, the highest total sinkings of the war. This, however was the high point.

In May, the first convoys were introduced, and were immediately successful. Overall losses started to fall; losses to ships in convoy fell dramatically. In the three months following their introduction, on the Atlantic, North Sea, and Scandinavian routes, of 8,894 ships convoyed just 27 were lost to U-boats. By comparison 356 were lost sailing independently.

As shipping losses fell, U-boat losses rose; during the period May to July 1917, 15 U-boats were destroyed in the waters around Britain, compared to 9 the previous quarter, and 4 for the quarter before the campaign was renewed.

As the campaign became more intense, it also became more brutal. 1917 saw a series of attacks on hospital ship
Hospital ship
A hospital ship is a ship designated for primary function as a floating medical treatment facility or hospital; most are operated by the military forces of various countries, as they are intended to be used in or near war zones....

s, which generally sailed fully lit, to show their non-combatant status. In January, HMHS Rewa
HMHS Rewa was a steamship originally built for the British-India Steam Navigation Company, but requisitioned for use as a British hospital ship during the First World War...

was sunk by U-55; in March, HMHS Gloucester Castle
HMHS Gloucester Castle
HMHS Gloucester Castle was a steam ship originally built for the Union-Castle Line, but requisitioned for use as a British hospital ship during the First World War. On 31 March 1917 she was torpedoed by German U-boat UB-32. She was, however, salvaged, and returned to civilian service after the war...

by U-32; in June, HMHS Llandovery Castle
HMHS Llandovery Castle
The Llandovery Castle, built in 1914 in Glasgow as RMS Llandovery Castle for Union Castle Line, was a Canadian hospital ship torpedoed off southern Ireland on 27 June 1918 with the loss of 234 lives....

by U-86.

As U-boats became more wary, encounters with Q-ship
Q-ships, also known as Q-boats, Decoy Vessels, Special Service Ships, or Mystery Ships, were heavily armed merchant ships with concealed weaponry, designed to lure submarines into making surface attacks. This gave Q-ships the chance to open fire and sink them...

s also became more intense. In February 1917 U-83 was sunk by Farnborough
HMS Farnborough
HMS Farnborough, also known as , was a Q-ship of the British Royal Navy that saw service in the First World War. Farnborough was a heavily armed merchant ship with concealed weaponry that was designed to lure submarines into making surface attacks. Farnborough sank two submarines in her service in...

, but only after Gordon Campbell, Farnborough’s captain, allowed her to be torpedoed in order to get close enough to engage.
In March Privet sank U-85 in a 40-minute gun battle, but herself sank before reaching harbour.

In April Heather was attacked by U-52 and was badly damaged; the U-boat escaped unscathed. And a few days later Tulip was sunk by U-62 whose captain was suspicious of her appearance.

1918: final year

The convoy system was effective in reducing allied shipping losses, while better weapons and tactics made the escorts more successful at intercepting and attacking U-boats. Shipping losses in Atlantic waters were 98 ships (just over 170, 00 GRT) in January; after a rise in February they fell again, and did not rise above that level for the rest of the war.

In January , 6 U-boats were destroyed in the theatre; this also became the average loss for the year.

The Allies continued to try and block access through the Straits of Dover, with the Dover Barrage. Until November 1917 it was ineffective; up to then just 2 U-boats had been destroyed by the Barrage force, and the Barrage itself had been a magnet for surface raids. After major improvement in the winter of 1917 it became more effective; in the four-month period after mid-December seven U-boats were destroyed trying to transit the area, and by February the High Seas Flotilla boats had abandoned the route in favour of sailing north-about round Scotland, with a consequent loss of effectiveness. The Flanders boats still tried to use the route, but continued to suffer losses, and after March switched their operations to Britain’s east coast.

Other measures, particularly against the Flanders flotilla, were the raids on Zeebrugge
Zeebrugge Raid
The Zeebrugge Raid, which took place on 23 April 1918, was an attempt by the British Royal Navy to neutralize the key Belgian port of Bruges-Zeebrugge...

 and Ostend
First Ostend Raid
The First Ostend Raid was the first of two attacks by the Royal Navy on the German-held port of Ostend during the late spring of 1918 during the First World War...

, an attempt to blockade access to the sea. These were largely unsuccessful; the Flanders boats were able to maintain access throughout this period.

May 1918 saw the only attempt by the Germans to muster a group attack, the forerunner of the wolf-pack, to counter the Allied convoys.

In May, 6 U-boats sailed, under the command of K/L Rucker in U-103. On 11 May U-86 sank one of a pair of ships detached from a convoy in the Channel, but the next day an attack on the troopship Olympic
RMS Olympic
RMS Olympic was the lead ship of the Olympic-class ocean liners built for the White Star Line, which also included Titanic and Britannic...

 led to the destruction of U-103, while UB-72 was sunk by British submarine D-4
HMS D4 was a British D class submarine built by Vickers, Barrow. D4 was laid down on 24 February 1910, launched 27 April 1911 and was commissioned on 29 November 1911...

. Two more ships were sunk in convoys in the next week, and three independents, but over 100 ships had passed through the groups patrol area in safety.

During the summer, the extension of the convoy system and effectiveness of the escorts made the east coast of Britain as dangerous for the U-boats as the Channel had become. In this period, the Flanders flotilla lost a third of its boats, and in the autumn, losses were at 40%. In October, with the German army in full retreat
Hundred Days Offensive
The Hundred Days Offensive was the final period of the First World War, during which the Allies launched a series of offensives against the Central Powers on the Western Front from 8 August to 11 November 1918, beginning with the Battle of Amiens. The offensive forced the German armies to retreat...

, the Flanders flotilla was forced to abandon its base at Bruges
Bruges is the capital and largest city of the province of West Flanders in the Flemish Region of Belgium. It is located in the northwest of the country....

 before it was over-run. A number of boats were scuttled there, while the remainder, just 10 boats, returned to bases in Germany.

In the summer, too, steps were taken to reduce the effectiveness of the High Seas Flotillas. In 1918 the Allies, particularly the Americans, undertook to create a barrage across the Norwegian Sea
Norwegian Sea
The Norwegian Sea is a marginal sea in the North Atlantic Ocean, northwest of Norway. It is located between the North Sea and the Greenland Sea and adjoins the North Atlantic Ocean to the west and the Barents Sea to the northeast. In the southwest, it is separated from the Atlantic Ocean by a...

, to block U-boat access to the Western Approaches by the north-about route. This huge undertaking involved laying and maintaining minefields and patrols in deep waters over a distance of 300 nautical miles (556 kilometers). The North Sea Mine Barrage saw the laying of over 70,000 mines, mostly by the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

, during the summer of 1918. From September to November 1918 6 U-boats were sunk by this measure.

On 11 November 1918, World War I ended. The last task of the U-Boat Arm was in helping to quell the Wilhelmshaven mutiny
Wilhelmshaven mutiny
The Kiel mutiny was a major revolt by sailors of the German High Seas Fleet on 3 November 1918. The revolt triggered the German revolution which was to sweep aside the monarchy within a few days. It ultimately led to the end of the First World War and to the establishment of the Weimar Republic.-...

, which had broken out when the High Seas Fleet
High Seas Fleet
The High Seas Fleet was the battle fleet of the German Empire and saw action during World War I. The formation was created in February 1907, when the Home Fleet was renamed as the High Seas Fleet. Admiral Alfred von Tirpitz was the architect of the fleet; he envisioned a force powerful enough to...

 was ordered to sea for a final, doomed sortie. After the Armistice
Armistice with Germany (Compiègne)
The armistice between the Allies and Germany was an agreement that ended the fighting in the First World War. It was signed in a railway carriage in Compiègne Forest on 11 November 1918 and marked a victory for the Allies and a complete defeat for Germany, although not technically a surrender...

, the remaining U-boats joined the High Seas Fleet in surrender, and were interned at Harwich
Harwich Force
The Harwich Force was a squadron of the Royal Navy, formed during the First World War, that went on to play a significant role in the war.-History:...


Of the 12½ million tons of Allied shipping destroyed in World War I, over 8 million tons, two thirds of the total, had been sunk in the waters of the Atlantic war zone. Of the 178 U-boats destroyed during the war, 153 had been from the Atlantic forces, 77 from the much larger High Seas Flotillas and 76 from the much smaller Flanders force.


Date Ships sunk (HSF) Tonnage Ships sunk (Flanders) Tonnage U-boats destroyed (HSF) U-boats destroyed (Flanders)
1914 3 2,950 N/A N/A 5 N/A
1915 390 700,782 131 90,295 11 2
1916 350 508,745 512 604,151 7 12
1917 not recorded 2,895,983 not
1,607,389 29 31
1918 435 1,044,822 327 558,760 25 31

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.