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U-boat is the anglicized version of the German word About this sound U-Boot , itself an abbreviation of Unterseeboot (undersea boat), and refers to military submarines operated by Germany, particularly in World War I and World War II. Although in theory, U-boats could have been useful fleet weapons against enemy naval warships, in practice they were most effectively used in an economic-warfare role (commerce raiding), enforcing a naval blockade against enemy shipping. The primary targets of the U-boat campaigns in both wars were the merchant convoys bringing supplies from the British Empire and the United States to the islands of Great Britain. Austrian submarines of World War I were also known as U-boats.

The distinction between U-boat and submarine is common in English-language usage (where U-boat refers exclusively to the German vessels of the World Wars) but is unknown in German, in which the term U-Boot refers to any submarine.


The first submarine built in Germany was the Brandtaucher, designed in 1850 by the inventor and engineer Wilhelm Bauer and built by Schweffel & Howaldt in Kiel for the German Navy.

This was followed in 1890 by W1 and W2, built to a Nordenfelt design. In 1904, Krupp's dockyard in Kiel completed a submarine which was sold to Russia. The first works were carried out by the Spanish engineer Raymondo Lorenzo d'Equevilley Montjustin (submarine Narval). The first unit for the German Navy was built in 1905. This was the Karp-class which had a double hull, was powered by a Körting kerosene engine and armed with a single torpedo tube. It was designated U-1, with the 50% larger U-2 design having two tubes. A diesel engine was not installed in a German Navy boat until the U-19-class of 1912–13. At the start of World War I, Germany had 48 submarines of 13 classes in service or under construction.

German submarine U-9 (1910).

At the start of World War I, Germany had twenty-nine U-boats in service; in the first ten weeks, five British cruisers had been lost to them. In September, U-9 sank the obsolete British warships HMS Aboukir, Cressy and Hogue (the "Live Bait Squadron") in a single hour.

For the first few months of the war, U-boat anti-commerce actions observed the "prize rules" of the time which governed the treatment of enemy civilian ships and their occupants. On 20 October 1914, U-17 sank the first merchant ship, the SS Glitra, off Norway.[1] Surface commerce raiders were proving to be ineffective, and on 4 February 1915, the Kaiser assented to the declaration of a war zone in the waters around the British Isles. This was cited as a retaliation for British minefields and shipping blockades. Under the instructions given to U-boat captains, they could sink merchant ships, even potentially neutral ones, without warning. A statement by the U.S. Government, holding Germany "strictly accountable" for any loss of American lives, made no material difference.[citation needed]

On 7 May 1915, U-20 sank the liner RMS Lusitania with a single torpedo hit. The sinking claimed 1,198 lives, 128 of them American civilians, including noted theatrical producer Charles Frohman and Alfred Vanderbilt, a member of the prestigious Vanderbilt family. The sinking deeply shocked the Allies and their sympathizers because an unarmed civilian merchant vessel was attacked. According to the ship's manifest, Lusitania was carrying military cargo.[2] After further investigations, it has been confirmed that the Lusitania was in fact carrying ammunition for the allies to use against the Germans. However, this was not known at the time and the Lusitania was mistaken for a troopship. It was not until the sinking of the ferry Sussex that there was a widespread reaction in the USA.

The initial U.S. response was to threaten to sever diplomatic relations, which persuaded the Germans to re-impose restrictions on U-boat activity. The U.S. reiterated its objections to German submarine warfare whenever U.S. civilians died as a result of German attacks, which prompted the Germans to fully re-apply prize rules. This, however, removed the effectiveness of the U-boat fleet, and the Germans consequently sought a decisive surface action, a strategy which culminated in the Battle of Jutland.

Although the Germans claimed victory at Jutland, the British Grand Fleet remained in control at sea. It was necessary to return to effective anti-commerce warfare by U-boats. Vice-Admiral Reinhard Scheer, Commander in Chief of the High Seas Fleet, pressed for all-out U-boat war, convinced that a high rate of shipping losses would force Britain to seek an early peace before the United States could react effectively.

U-boat sinking a troop transport ship, painting by Willy Stöwer

The renewed German campaign was effective, sinking 1.4 million tons of shipping between October 1916 and January 1917. Despite this, the political situation demanded even greater pressure, and on 31 January 1917, Germany announced that its U-boats would engage in unrestricted submarine warfare beginning 1 February. On 17 March, German submarines sank three American merchant vessels, and the U.S. declared war on Germany in April 1917.

In the end, the German strategy failed to destroy sufficient Allied shipping, largely due to the introduction of escorted convoys, before U.S. manpower and materiel could be brought to bear in France. However, the main reason for the ending of the war was the effectiveness of the British blockade of Germany which brought about an economic collapse. An armistice became effective on 11 November 1918 and all surviving German submarines were surrendered. Of the 360 submarines that had been built, 178 were lost but more than 11 million tons of shipping had been sunk.


Surrender of the Fleet

Under the terms of the Armistice, all U-boats were to immediately surrender. Those in home waters sailed to the British submarine base at Harwich. The entire process was done quickly and in the main without difficulty, after which the vessels were studied, scrapped, or given to Allied navies. Stephen King-Hall wrote a detailed eyewitness account of the surrender.[3]


At the end of World War I, as part of the Paris Peace Conference, 1919, the Treaty of Versailles restricted the total tonnage of the German surface fleet. The treaty also restricted the independent tonnage of ships and forbade the construction of submarines. However, a submarine design office was set up in Holland and a torpedo research programme was started in Sweden. Before the start of World War II, Germany started building U-boats and training crews, labeling these activities as "research" or concealing them using other covers. When this became known, the Anglo-German Naval Agreement limited Germany to parity with Britain in submarines.[4] When World War II started, Germany already had 65 U-boats, with 21 of those at sea ready for war.

World War II

During World War II, U-boat warfare was the major component of the Battle of the Atlantic, which lasted the duration of the war. Germany had the largest submarine fleet in World War II, since the Treaty of Versailles had limited the surface navy of Germany to six battleships (of less than 10,000 tons each), six cruisers and 12 destroyers.[5] Prime Minister Winston Churchill wrote "The only thing that really frightened me during the war was the U-Boat peril".

U-boat Pens in Saint-Nazaire, France

In the early stages of the war, the U-boats were extremely effective in destroying Allied shipping, initially in the mid-Atlantic, where neither Canadian nor British based escorts provided cover. There was an extensive trade in war supplies and food across the Atlantic, which was critical for Britain's survival. This continuous action became known as the Battle of the Atlantic, as the British developed technical defences such as ASDIC and RADAR, and the German U-Boats responded by hunting in what were called "wolf packs" where multiple submarines would stay close together making it easier for them to sink a specific target. Later, when the USA entered the war, the U-boats ranged from the Atlantic coast of the United States and Canada to the Gulf of Mexico, and from the Arctic to the west and southern African coasts and even as far east as Penang. The U.S. military engaged in various tactics against German incursions in the Americas, these included military surveillance of foreign nations in Latin America, particularly in the Caribbean, in order to deter any local governments from supplying German U-boats.

Because speed and range were severely limited underwater while running on battery power, U-boats were required to spend most of their time surfaced running on diesel engines, diving only when attacked or for rare daytime torpedo strikes. The most common U-boat attack during the early years of the war was conducted on the surface and at night, see submarine warfare. This period, before the Allied forces developed truly effective antisubmarine warfare (ASW) tactics, was referred to by German submariners as "die glückliche Zeit" or "the happy time."[6]

U-534, Birkenhead Docks, Merseyside, England


The U-boat was essentially a launch platform for its main weapon, the torpedo, though mines were also used. By the end of the war, almost 3,000 Allied ships (175 warships; 2,825 merchant ships) were sunk by U-boat torpedoes.[7] Early German World War II torpedoes were straight runners, unlike the homers and pattern-runners of later in the war. They were fitted with one of two types of pistol trigger: impact, which detonated the warhead upon contact with a solid object, and magnetic, which detonated upon sensing a change in the magnetic field within a few meters. One of the most effective uses of magnetic pistols would be to set the torpedo's depth to just beneath the keel of the target. The explosion under the target's keel would create a shock wave, and the ship could break in two. In this way, even large or heavily-armored ships could be sunk or disabled with a single well-placed hit. In practice, however, the depth-keeping equipment and magnetic and contact exploders were notoriously unreliable in the first eight months of the war. Torpedoes would often run at an improper depth, detonate prematurely, or simply fail to explode. This was most evident in Operation Weserübung, the invasion of Norway, where various skilled U-Boat commanders failed to inflict damage on British transports and warships because of faulty torpedoes. The faults were largely due to a lack of testing. The magnetic detonator was sensitive to mechanical oscillations during the torpedo run and was eventually phased out, and the depth-keeping problem was solved by early 1942.[8]

Later in the war, Germany developed an acoustic homing torpedo, the G7es. It was primarily designed to combat convoy escorts. The acoustic torpedo was designed to run straight to an arming distance of 400 meters and then turn toward the loudest noise detected. This sometimes ended up being the U-boat itself; at least two submarines may have been sunk by their own homing torpedoes. (Problems with steering mechanisms on normal torpedoes made them occasionally lethal to the firing boat as well). Additionally, it was found these torpedoes were only effective against ships moving at greater than 15 knots (28 km/h). At any rate, the Allies countered acoustic torpedoes with noisemaker decoys such as Foxer, FXR, CAT and Fanfare.

U-boats also adopted "pattern-running" torpedoes which ran to a preset distance, then traveled in either a circular or ladder-like pattern. When fired at a convoy, this increased the probability of a hit if the weapon missed its primary target.

U-boat developments

During World War II, the Kriegsmarine produced many different types of U-boats as technology evolved. Most notable are Type VII, known as the "workhorse" of the fleet, which was by far the most-produced type; Type IX boats were larger and specifically designed for long-range patrols, some traveling as far as Japan. With the Type XXI "Elektroboot", German designers realized the U-boat depended on submerged ability both for survival and stealth. The Type XXI featured a revolutionary streamlined hull design and propulsion system with a large battery which allowed it to cruise submerged for long periods and reach unprecedented submerged speeds. A larger battery was possible because the space it occupied was originally intended to store hydrogen peroxide for a Walter turbine which was unsuccessful on the Type XVII.

Throughout the war an arms race evolved between the Allies and the Kriegsmarine, especially in detection and counter-detection. Sonar (ASDIC in Britain) allowed allied warships to detect submerged U-boats (and vice versa) beyond visual range but was not effective against a surfaced vessel; thus, early in the war, a U-boat at night or in bad weather was actually safer on the surface. Advancements in radar became particularly deadly for the U-boat crews, especially once aircraft-mounted units were developed. As a countermeasure, U-boats were fitted with radar warning receivers, to give them ample time to dive before the enemy closed in. U-boat radar was also developed, but many captains chose not to utilize it for fear of broadcasting their position to enemy patrols.

The Germans took the idea of the Schnorchel (snorkel) from captured Dutch submarines, though they did not begin to implement it on their own boats until rather late in the war. The Schnorchel was a retractable pipe which supplied air to the diesel engines while submerged at periscope depth, allowing the boats to cruise and recharge their batteries while maintaining a degree of stealth. It was far from a perfect solution, however. There were problems with the device's valve sticking shut or closing as it dunked in rough weather; since the system used the entire pressure hull as a buffer, the diesels would instantaneously suck huge volumes of air from the boat's compartments, and the crew often suffered painful ear injuries. Waste disposal was a problem when the U-boats spent extended periods without surfacing. Speed was limited to 8 knots (15 km/h), lest the device snap from stress. The schnorchel also had the effect of making the boat essentially noisy and deaf in sonar terms. Finally, Allied radar eventually became sufficiently advanced such that the schnorchel head itself could be detected. The U-boats had a radar detector but the Allies changed to centimetric radar which the Germans did not discover.

The later U-boats were covered in a sound-absorbent rubber coating to make them less of an ASDIC target. They also had the facility to release a chemical bubble-making decoy, known as Bold, after the mythical kobold.



Advances in convoy tactics, high frequency direction finding (referred to as "Huff-Duff"), radar, active sonar (called ASDIC in Britain), depth charges, ASW spigot mortars (also known as "hedgehog"), the intermittent cracking of the German Naval Enigma code, the introduction of the Leigh Light, the range of escort aircraft (especially with the use of escort carriers), and the full entry of the U.S. into the war with its enormous shipbuilding capacity, all turned the tide against the U-boats. In the end, the U-boat fleet suffered extremely heavy casualties, losing 793 U-boats and about 28,000 submariners (a 75% casualty rate).

Survivors from U-175 after being sunk by USS Spencer, April 17, 1943

At the same time, the Allies targeted the U-boat shipyards and their bases with strategic bombing.

Enigma machine

The British had a major advantage in their ability to read some German naval Enigma codes. An understanding of the German coding methods had been brought to Britain via France from Polish code-breakers. Thereafter, code-books and equipment were captured by raids on German weather ships and from captured U-boats. A team including Alan Turing used special purpose "Bombes" and early computers to break new German codes as they were introduced. The speedy decoding of messages was vital in directing convoys away from wolf-packs and allowing interception and destruction of U-boats. This was demonstrated when the Naval Enigma machines were altered in February 1942 and wolf-pack effectiveness greatly increased until the new code was broken.

The U-110, a Type IXB, was captured in 1941 by the Royal Navy, and its Enigma machine and documents were removed. Further code books were captured by raids on weather ships. The U-505, a Type IXC, was captured by the United States Navy in 1944. It is presently a museum ship in Chicago at the Museum of Science and Industry. The U-505 was captured along with the current codebooks, but there were fears that a security breach would alert the Germans to the capture of their codes.

Battle of the St. Lawrence

Two events in the St Lawrence took place in 1942 when German U-boats attacked four allied ore carriers at Bell Island, Newfoundland. The carriers SS Saganaga and the SS Lord Strathcona were sunk by U-513 on September 5, 1942, while the SS Rosecastle and PLM 27 were sunk by U-518 on November 2 with the loss of 69 lives. When the submarine launched a torpedo at the loading pier, Bell Island became the only location in North America to be subject to direct attack by German forces in World War II.

Operation Deadlight

Operation Deadlight was the code name for the scuttling of U-boats surrendered to the Allies after the defeat of Germany near the end of the war. Of the 154 U-boats surrendered, 121 were scuttled in deep water off Lisahally, Northern Ireland or Loch Ryan, Scotland in late 1945 and early 1946.

Post World War II

U-15, a Type 206 submarine, of the German Navy at the Kiel Week 2007

From 1955, the West German Bundesmarine was allowed to have a small navy. Initially two sunken Type XXIIIs and a Type XXI were raised and repaired. In the 1960s, West Germany re-entered the submarine business. Because Germany was initially restricted to a 450 tonne displacement limit, the Bundesmarine focused on small coastal submarines to protect against the Soviet threat in the Baltic Sea. The Germans sought to use advanced technologies to offset the small displacement, such as amagnetic steel to protect against naval mines and magnetic anomaly detectors.

The initial Type 201 was a failure because of hull cracking; the subsequent Type 205, first commissioned in 1967, was a success, and 12 were built for the German navy. To continue the U-Boat tradition, the new boats received the classic U designation starting with the U-1.

With the Danish government's purchase of two Type 205 boats, the German government realized the potential for the submarine as an export. Three of the improved Type 206 boats were sold to the Israeli Navy becoming the Gal-class. The German Type 209 diesel-electric submarine was the most popular export-sales submarine in the world from the late 1960s into the first years of the 21st century. With a larger 1,000-1,500 tonne displacement, the class was very customizable and has seen service with 14 navies with 51 examples being built as of 2006.

Germany has brought the U-Boat name into the 21st century with the new Type 212. The 212 features an air-independent propulsion system using hydrogen fuel cells. This system is safer than previous closed-cycle diesel engines and steam turbines, cheaper than a nuclear reactor and quieter than both. While the Type 212 is also being purchased by Italy, the Type 214 has been designed as the follow-on export model and has been sold to Greece, South Korea and Turkey.

In July 2006, Germany commissioned its newest U-boat, the U-34, a Type 212.


  • Das Boot (1981) is a critically acclaimed German movie and television mini-series about life aboard a U-Boat. It was adapted from a novel of the same name by war correspondent Lothar-Günther Buchheim.
  • The Enemy Below and the more recent U-571 are movies revolving around World War II submarine warfare.
  • The book Shadow Divers by Robert Kurson tells the story of the discovery and identification of the wreck of U-869 by divers off the coast of New Jersey.
  • In Hugo Pratt's A Ballad of the Salt Sea, the first comic novel featuring the character Corto Maltese, one of the main characters is Christian Slutter, a lieutenant in the Imperial German Navy, who is in command of a U-boat. The submarine itself plays quite an important role in the story.
  • Silent Hunter 3 is a simulation game where the player takes control of a german U-Boot during WWII

See also

Type 212 submarine with air-independent propulsion of the German Navy in dock at HDW/Kiel



  1. ^ "WWI U-Boats U-17". Retrieved 2008-03-24. 
  2. ^
  3. ^ A North Sea diary, 1914-1918, Chapter XIX
  4. ^ For other warships, Germany was permitted lesser amounts compared to the UK
  5. ^ Hakim, Joy (1995). A History of Us: War, Peace and all that Jazz. New York: Oxford University Press. pp. 100–104. ISBN 0-19-509514-6. 
  6. ^ Military History Online
  7. ^ Crocker III, H. W. (2006). Don't Tread on Me. New York: Crown Forum. pp. 310. ISBN 9781400053636. 
  8. ^ Karl Dönitz. Memoirs: Ten Years and Twenty Days. Naval Institute Press. p. 482. ISBN 0-87021-780-1. 


  • John Abbatiello. Anti-Submarine Warfare in World War I: British Naval Aviation and the Defeat of the U-Boats (2005)
  • Buchheim, Lothar-Günther, Das Boot (Original German edition 1973, eventually translated into English and many other Western languages). Movie adaptation in 1981, directed by Wolfgang Petersen
  • Gannon, Michael (1998) Black May. Dell Publishing. ISBN 0-440-23564-2
  • Gannon, Michael (1990) Operation Drumbeat. Naval Institute Press. ISBN 978-1-59114-302-4
  • Gray, Edwyn A. The U-Boat War, 1914-1918 (1994)
  • Kurson, Robert (2004). Shadow Divers: The True Adventure of Two Americans Who Risked Everything to Solve One of the Last Mysteries of World War II. Random House Publishing. ISBN 0-375-50858-9
  • Preston, Anthony (2005). The World's Greatest Submarines.
  • Stern, Robert C. (1999). Battle Beneath the Waves: U-boats at war. Arms and Armor/Sterling Publishing. ISBN 1-85409-200-6.
  • van der Vat, Dan. The Atlantic Campaign Harper & Row, 1988. Connects submarine and antisubmarine operations between World War I and World War II, and suggests a continuous war.

Further reading

  • Möller, Eberhard and Werner Brack. The Encyclopedia of U-Boats: From 1904 to the Present (2006) ISBN 1-85367-623-3
  • Showell, Jak Mallmann. The U-boat Century: German Submarine Warfare, 1906-2006 (2006) ISBN 1-59114-892-8
  • Georg von Trapp and Elizabeth M. Campbell. To the Last Salute: Memories of an Austrian U-Boat Commander (2007)
  • Westwood, David. U-Boat War: Doenitz and the evolution of the German Submarine Service 1935 - 1945 (2005) ISBN 1-932033-43-2
  • Werner, Herbert. Iron Coffins: A Personal Account of the German U-Boat Battles of World War II ISBN 978-0304353309
  • Von Scheck, Karl. U122: The Diary of a U-boat Commander Diggory Press ISBN 978-1846850493

External links


Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary




A calque of German U-Boot.


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U-boat (plural U-boats)

  1. Any German submarine of the First or Second World War, or any Austro-Hungarian submarine of the First World War.


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