U-Boot or Unterseeboot (militarily also Uboot; English: under-sea-boat; anglicised: U-boat) is the German term for submarine. They were used by the Kaiserliche Marine, the Austro-Hungarian Navy of the Dual Monarchy as well as the Kriegsmarine and are still used by the German Navy of the Bundeswehr (branch of arms: U-Boot-Waffe or U-boat weapon) as an important feature of sea or naval power (Seemacht).
The first submarine built in Germany, the three-man "Brandtaucher" (Incendiary or Fire Diver), sank to the bottom of Kiel harbor on 1 February 1851 during a test dive. The inventor and engineer Wilhelm Bauer (1822–1875) had designed this vessel in 1850, and Schweffel & Howaldt constructed it in Kiel and was let to water for the first time on 18 December 1850. Bauer had taken part in the Schleswig-Holstein War in 1849 as a soldier in the Bavarian auxiliary corps. There he had the idea for a weapon that could operate under the sea surface, in this case under the Alssund. Because his plans did not arouse any interest in Bavaria, he returned to Schleswig-Holstein and was able to deal with the project there as a non-commissioned officer in the Schleswig-Holstein army. Dredging operations in 1887 rediscovered Brandtaucher; it was later raised and put on historical display in Imperial Germany.
Since World War I, nautical technology has evolved at a rapid rate, but in 1914 U-boats were considered quite advanced. These vessels could reach maximum depths of 50 meters or 165 feet, achieve speeds of 16 knots at the surface and eight knots underwater, and had a range of up to 25,000 miles. They were armed with deck-mounted guns and up to 16 self-propelled torpedoes. Since torpedoes of this period could be unreliable, surface attacks were quite common; this tactic also allowed U-boat crews to seize supplies and valuables from merchant ships before they sunk. Furthermore, some U-boats were equipped to transport and deploy naval mines.
At the outbreak of the war, Germany had only twenty submarines immediately available for combat, although these included vessels of the diesel-engined U-19 class, which had a sufficient range of 5,000 miles (8,000 km) and speed of 8 knots (15 km/h) to allow them to operate effectively around the entire British coast. By contrast, the Royal Navy had a total of 74 submarines, though of mixed effectiveness. In August 1914, a flotilla of ten German U-boats sailed from their base in Heligoland to attack Royal Navy warships in the North Sea in the first submarine war patrol (Feindfahrt) in history.
Submarine warfare played an integral role in the mounting international pressures of World War I. After the war broke out in 1914, Great Britain used its powerful navy to blockade German ports to limit food, supplies, and war materials from reaching the German military and people. Great Britain declared German waters a war zone and seized cargoes bound for the Central Powers (Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria).
- In the opening days of WW1, Unterseeboots, better known simply as U-boats, proved to be a potent and constant threat to Allied ships, with one U-boat identified as SM U-9 infamously killing nearly 1,500 British sailors in less than an hour by sinking three armoured British cruisers on September 22, 1914. That same U-boat would go on to sink over a dozen British ships during its naval career, with targets ranging from small fishing boats caught in open water to the Edgar-class protected cruiser, HMS Hawke. The reason for the U-boat success in the early going of the war was, in part, due to the fact that when they were submerged they were undetectable by technology of the day. Another factor that played into German hands is that the Allies, especially the British, consistently downplayed the danger posed by submarines and their value in combat. In fact, at first British Naval brass simply refused to acknowledge that U-boats were sinking ships. For example, the aforementioned actions of U-boat SM U-9 were initially attributed to mines. In short, British Naval officers had little faith in the potential of submarines and wrote them off as a mere fascination that had no real potential in combat beyond novelty. Thus, they did little at first to try to come up with viable ways to combat them. Things got real, however, when U-boats like SM U-9 began targeting British supply ships, almost bringing the country to its knees when it found itself unable to secure even basic provisions for its citizens and factories.
Britain's blockade across the North Sea and the English Channel cut the flow of war supplies, food, and fuel to Germany during World War I. Germany retaliated by creating its own blockade around the British Isles and English Channel and by using its submarines to destroy all ships that were supplying the Allies. The formidable U-boats of the Kaiserliche Marine prowled the Atlantic armed with torpedoes. They were Germany’s only weapon of advantage as the Royal Navy effectively blocked German ports to supplies. Germany built new and larger U-boats to punch holes in the British blockade, which was threatening to starve Germany out of the war. In 1914, Germany had just 20 U-boats. By 1917, it had 140 and the U-boats had destroyed about 30 percent of the world's merchant ships.
- Germany was the first country to employ submarines in war as substitutes for surface commerce raiders. At the outset of World War I, German U-boats, though numbering only 38, achieved notable successes against British warships; but because of the reactions of neutral powers (especially the United States) Germany hesitated before adopting unrestricted U-boat warfare against merchant ships. The decision to do so in February 1917 was largely responsible for the entry of the United States into the war. The U-boat campaign then became a race between German sinkings of merchant ships and the building of ships, mainly in the United States, to replace them. In April 1917, 430 Allied and neutral ships totaling 852,000 tons were sunk, and it seemed likely that the German gamble would succeed. However, the introduction of convoys, the arrival of numerous U.S. destroyers, and the vast output of American shipyards turned the tables. By the end of the war Germany had built 334 U-boats and had 226 under construction. The peak U-boat strength of 140 was reached in October 1917, but there were never more than about 60 at sea at one time. In 1914–18 the destruction—more than 10,000,000 tons—caused by the U-boats was especially remarkable in view of the small size (less than l,000 tons), frailty, and vulnerability of the craft.
On 5 December 1916, David Lloyd George became Prime Minister of Great Britain. On 12 December 1916, the German Government submitted a peace proposal addressed to the still neutral USA, and the Pope, requesting their arbitration for peace. On 18 December 1916, Woodrow Wilson submitted his peace note to the belligerents. On the penultimate day of December 1916, the Allies refused the German peace offer, and the German high command under Alfred von Tirpitz was forced to return to the policy of unrestricted submarine warfare (uneingeschränkter U-Boot-Krieg), engineering the dismissal of opponents of the policy that aimed to sink more than 600,000 tons of shipping a month. Germany was already experiencing food shortages and had imposed unpopular compulsory service either in armed forces or war industries. Although President Wilson formally broke diplomatic relations in February 1917, he was still unsure how far public support had moved. He declined to ask Congress for a declaration of war at that time, arguing that Germany had still not committed any “actual overt acts” warranting a military response, but on 6 April 1917 the USA declared war on Germany.
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. The use of Q-ships contributed to the abandonment of cruiser rules restricting attacks on unarmed merchant ships and to the shift to unrestricted submarine warfare in the 20th century. Their codename referred to the vessels' home port, Queenstown, in Ireland. These became known by the Germans as a U-Boot-Falle ("U-boat trap"). A Q-ship would appear to be an easy target, but in fact carried hidden armaments. A typical Q-ship might resemble a tramp steamer sailing alone in an area where a U-boat was reported to be operating. German U-boats, which were tasked with sparing civilians and only confiscating merchant ships, appeared to search the ship, were then shot at and the crews brutally massacred. For example, SM U 27 and SM U 41 were sunk by the English submarine trap HMS "Baralong", which had disguised itself with a false flag as a US-American and therefore neutral ship, which was therefore not allowed to be attacked by German U-boats.
About a dozen of the U-boat sailors of SM U 27 survived on 19 August 1915 and swam towards the merchant ship "Nicosian". The commanding officer of the HMS "Baralong", Lieutenant-Commander Godfrey Herbert (later known as "Baralong Herbert"), ordered the German survivors to be shot in the water and sent a boarding party to murder all who had made it aboard. The Germans were discovered in the engine room and shot on sight. This war crime with 37 dead became known as the first "Baralong incident". The Admiralty, upon receiving Herbert's report, immediately ordered its suppression, but the strict censorship imposed on the event failed when Americans who had witnessed the incident from Nicosian's lifeboats spoke to newspaper reporters after their return to the United States. The bloody deed of HMS "Baralong" actions caused the Kaiserliche Marine to cease conforming to the Prize Rules and to practise unrestricted submarine warfare. The German Reichskanzler, Theobald von Bethmann Hollweg, condemned the killings. A German medal was issued commemorating the event. In October 1915, "Baralong" was renamed HMS Wyandra to conceal her identity. On 24 September 1915, SM U 41 was sunk by gunfire from Q-Ship "Baralong" in the Western Approaches, 35 German seamen were killed, two luckily survived, one was the First Officer, Oberleutnant zur See Iwan Crompton, who was seriously wounded ("Baralong" had run down the lifeboat he was in; he leapt clear and was soon afterward taken aboard). After stopping 6,651 gross register tons (GRT) merchantman "Urbino", U 41 under Kapitänleutnant Claus Hansen sent a boarding party aboard to inspect the cargo. After finding war material on board, the Germans put the merchant crew off the ship in the lifeboats in order to spare them. U 41 was in the process of sinking "Urbino" with gunfire when HMS "Wyandra" (in the guise of the American-flagged merchantman "Baralong") arrived on the scene, flying an American flag. When U 41 approached, "Wyandra", fired on and sank the U-boat without striking the American flag. This was a violation of the rules of war; while the use of a False Flag was allowed, it was required that a belligerent identify itself before initiating hostilities.
Knights of the deep (Ritter der Tiefe)
In terms of tonnage, Lieutenant-Captain Lothar von Arnauld de la Perière comes first with over 400,000 tons, followed by Lieutenant-Captain Walter Forstmann with 380,000 tons and Lieutenant-Captain Max Valentiner with 300,000 tons. All three have achieved most of their successes in the Mediterranean. In terms of the number of ships sunk, Commander Lieutenant Otto Steinbrinck is the leader with 216 ships during 24 enemy patrols (Feindfahrten). Over or nearly 100,000 tons were achieved by another 43 commanders. In addition to the Commander-in-Chief of the U-boats and the Commander-in-Chief of the U-boats in Flanders, 29 commanders received the highest medal of war "Pour le Mérite" for their and their crews' outstanding service. The successes achieved are particularly great when one considers the relatively small number of submarines Germany usually had. The maximum number of submarines available at one time was 140. Of these, about a third were available on the enemy at any one time. In total, Germany had 343 U-boats during the war, 199 of which sank in front of the enemy. More than half of the fighting U-boat crews died heroic deaths: 5,132 men. Other U-boat aces were
- Hans Rose,
- Walther Schwieger,
- Reinhold Saltzwedel
- Johannes Lohs,
- Waldemar Kophamel and
- Otto Schultze, but also
- Otto Eduard Weddigen,
- Hermann von Fischel,
- Helmut Patzig,
- Hans Nieland or
- Kurt Albrecht.
The Armistice dictations of 1918 forced Germany to surrender all its U-boats, and the Treaty of Versailles forbade it to possess them in the future. In 1935, however, the German government negotiated the right to build U-boats. German U-Boot "U-1", the first for the Kriegsmarine, was laid down on 11 February 1935, launched on 15 June 1935, commissioned on 29 June 1935 and sunk on 6 April 1940 north of Terschelling by a British mine in World War II. During World War II, U-boat warfare was the major component of the Battle of the Atlantic, which began in 1939 and ended with Germany's surrender in 1945. The Armistice of 11 November 1918 ending World War I had scuttled most of the old Imperial German Navy and the subsequent Treaty of Versailles of 1919 limited the surface navy of Germany's new Weimar Republic to only six battleships (of less than 10,000 tons each), six cruisers, and 12 destroyers. At the early stages of the war, the German Navy was only equipped with 57 750-ton Type VII U-boat, which was insuffient for Atlantic crossings and operations. To compensate, Germany's new navy, the Kriegsmarine, developed the largest submarine fleet going into World War II. British Prime Minister Winston Churchill later wrote
- "... the only thing that ever really frightened me during the war was the U-boat peril".
In saying this, he correctly identified the importance of the threat posed during World War Two by German U-boats to the Atlantic lifeline. In the early stages of the war, the U-boats were extremely effective in destroying Allied shipping due to the large gap in mid-Atlantic air cover through the Royal Air Force. Cross-Atlantic trade in war supplies and food was extensive and critical for Britain's survival. The continuous action surrounding British shipping 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 "wolfpacks", where multiple submarines would stay close together, making it easier for them to sink a specific target. Britain's vulnerable shipping situation existed until 1942, when the tides changed as the U.S. merchant marine and Navy entered the war, drastically increasing the amount of tonnage of supplies sent across the Atlantic. The combination of increased tonnage and increased naval protection of shipping convoys made it much more difficult for U-boats to make a significant dent in British shipping. Once the United States entered the war, 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, to deter any local governments from supplying German U-boats.
- Britain was ill-prepared in 1939 for a resumption of unrestricted submarine warfare, and during the early months of World War II the U-boats, which at that time numbered only 57, again achieved great successes. The first phase, during which the U-boats generally operated singly, ended in March 1941, by which time many merchant ships were sailing in convoy, trained escort groups were becoming available, and aircraft were proving their effectiveness as anti-U-boat weapons. In the next phase the Germans, having acquired air and U-boat bases in Norway and western France, were able to reach much farther out into the Atlantic, and their U-boats began to operate in groups (called wolf packs by the British). One U-boat would shadow a convoy and summon others by radio, and then the group would attack, generally on the surface at night. These tactics succeeded until radar came to the aid of the escorts and until convoys could be given continuous sea and air escort all the way across the Atlantic in both directions. In March 1943, as in April 1917, the Germans nearly succeeded in cutting Britain’s Atlantic lifeline, but by May escort carriers and very-long-range reconnaissance bombers became available. After the U-boats lost 41 of their number during that month, they withdrew temporarily from the Atlantic. In the next phase, U-boats were sent to remote waters where unescorted targets could still be found. Although at first they achieved considerable successes, especially in the Indian Ocean, the Allied strategy of striking at the U-boats’ supply vessels and putting all possible shipping into convoys again proved successful. In the final phase the U-boats—then fitted with the snorkel (schnorkel) ventilating tube, which permitted extended underwater travel and greatly reduced the effectiveness of radar—returned to the coastal waters around the British Isles, but they sank few ships and themselves suffered heavy losses. In World War II Germany built 1,162 U-boats, of which 785 were destroyed and the remainder surrendered (or were scuttled to avoid surrender) at the capitulation. Of the 632 U-boats sunk at sea, Allied surface ships and shore-based aircraft accounted for the great majority (246 and 245 respectively).
Operation "Paukenschlag" (Unternehmen „Paukenschlag“) was the alias for the surprise German attack on shipping off the East Coast of the United States beginning 11 January 1942, following their declaration of war against Germany on 11 December 1941. In the first wave just off the US coast, the five German U-boats sank 23 ships with over 150,000 GRT by the end of January 1942. Reinhard Hardegen had destroyed almost a third of the tonnage with U 123. For these achievements he received the Knight's Cross of the Iron Cross. Further waves of attacks with other submarines after the great success against the imperialist USA followed in the course of 1942. German U-boats inflicted considerable damage, sometimes within direct sight of New York: a total of 397 ships with over 2 million BRT to be sunk off the coast of North America. German losses in these sea areas over the same period were seven U-boats, with 302 crew lost their lives. In the waves that followed, the most successful submarine captains were often deployed, operating not only off the east coast but also in the Gulf of Mexico and the Caribbean, especially off Panama. Group "Monsun" or Wolfpack group "Monsun" (Wolfsrudelgruppe „Monsun“) was a group of German U-boats of the Kriegsmarine sent to the Indian Ocean and Arabian Sea during World War II to attack Allied ships. They operated from ports in the Dutch East Indies that had been occupied by Japan. Italian submarines were also used for supply purposes. The code name "Monsoon" was based on the plan to have the submarines reach the intended area of operations towards the end of the summer monsoon rains.
- "In 1943 and 1944 a total of 42 U-boats were deployed into East Asian waters. U 180 even twice. Only 13 boats escaped sinking. Eleven of these 'monsoon boats' called at Jakarta. Of these, five rest on the seabed. On October 5, 1944, U 168 under Lieutenant Pich left Jakarta for Surabaya. On the same day it was torpedoed by the Dutch submarine 'Zwaardfis' and sank to a depth of 45 m. 29 men in the forecastle were lost. Under the guidance of the captain, 11 men in the control center were able to 'climb out' from this dangerous depth. When they surfaced, they also found the 16 comrades who had been on deck alive. Suddenly the Dutch boat appeared and took everyone on board. This must be acknowledged as an outstanding human feat on the part of Captain van Goosen, for his boat was in enemy waters, and according to maritime law a U-boat, because of its own narrowness, need not pick up shipwrecked people. The courageous Dutch commander van Goosen even sent 23 rescued people back to the nearby Javanese coast with coastal sailors. Before they reached their comrades in Surabaya, however, they were first picked up by the Japanese as 'American spies' and severely mistreated. Capt. Pich, three other officers and a wounded man kept on board Captain van Goosen and brought them into Australian captivity. Many years later, the then naval base manager in Singapore, Lieutenant Commander Erhardt and van Goosen, representing their countries, were able to shake hands as friends at a NATO maneuver."
In the U-boat wafare of the Kriegsmarine from 1939 to 1945, a total of 863 of 1162 boats built were used in combat. 784 boats were lost during a patrol. Over 30,000 of the more than 40,000 U-boat crew members had fallen for the Vaterland. Overall, German U-boats sank at least 175 warships and 2,882 merchant ships, especially in the fight against enemy convoys, and hundreds of ships and port facilities were damaged.
- U-2540 was an advanced submarine which entered service on 24th February 1945. Less than 3 months later, on 4th May, she was scuttled by her own crew. In 1957, she was raised and returned to service on 1st September 1960 as the research submarine Wilhelm Bauer. She served in a civilian role under various research projects before decommissioning on 15th March 1982. On 24th April 1984, she was transferred to the Deutsches Schiffahrtsmuseum (German Maritime Museum) as the Technikmuseum Wilhelm Bauer.
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- Kapitän zur See Karl Boy-Ed: Amerika und der U-Boot-Krieg, Berlin 1918
- Korvettenkapitän Friedrich Lützow: Unterseebootskrieg und Hungerblockade, 1921
- Prof. Dr. jur. Heinrich Pohl: Der deutsche Unterseebootkrieg, 1925
- Vizeadmiral a. D. Andreas Michelsen: Der U-Boot-Krieg 1914–1918, Historischer Verlag Melchior, ISBN 978-3-939791-41-6
- Ernst Hashagen: U-Boote Westwärts – Meine Fahrten um England 1914–1918, 1943
- German U-boats of both World Wars, uboat.net
- German U-Boats and Battle of the Atlantic
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- Most successful U-boat Commanders: Commanders with over 100,000 tons sunk
- German U-boats in World War I
- German U-boats in World War II
- Führer der U-Boote (F.d.U.) / Befehlshaber der U-Boote (B.d.U.)
- Forgotten Super-Weapon of WW1: Type UC-1 Uboat
- Constructed in 1850 by Wilhelm Bauer-The Brandtaucher was the very first submarine project in Germany
- Aberdeen Daily Journal, 1 February 1915
- The Ridiculous Way British Sailors Were Ordered to Stop German U-boats During WWI
- U-boat (German submarine), Encyclopædia Britannica
- Werner von Langsdorff: U-Boote am Feind – 45 deutsche U-Boot-Fahrer erzählen, p. 11–12
- New Cutaway of Gernan Type-XXI Submarine
- The cutting edge U-boat was scuttled in 1945 was raised in 1957 & returned to service