- German:
- U-boot
- Abbreviation:
- of Unterseeboot
- Key People:
- Erich Ludendorff
- Paul von Hindenburg
- Karl Dönitz
- Related Topics:
- submarine
U-boat
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What is a U-boat?
A U-boat, from the German Unterseeboot ("undersea boat"), is a German submarine. U-boats gained notoriety for their effectiveness in destroying enemy shipping during both World War I and World War II.
Germany first used submarines in war to replace surface commerce raiders. Though initially only numbering 38, German U-boats had notable successes against British warships during World War I. By World War II, Germany had built 1,162 U-boats.
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Where does the name 'U-boat' come from?
The name "U-boat" comes from the German term Unterseeboot, which literally translates to "undersea boat". Germany was the first country to use submarines in war as substitutes for surface commerce raiders. Germany completed its first submarine, the U-1 (for Unterseeboot 1), in 1905. The destruction of enemy shipping by German U-boats was a feature of World Wars I and II.
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What was the main purpose of U-boats during wartime?
During wartime, German U-boats primarily aimed to disrupt enemy supply lines by attacking merchant ships. In both World War I and World War II, Germany employed U-boats to target Allied and neutral shipping, aiming to cripple their economies.
In World War I, unrestricted U-boat warfare contributed to the United States entering the war. Similarly, in World War II, U-boats initially achieved considerable success, but Allied countermeasures such as convoys, radar, and air support gradually reduced their effectiveness. Despite technological advancements like the snorkel, U-boats ultimately suffered heavy losses.
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How did U-boats affect naval battles in World War I and II?
During World War I and II, German U-boats significantly impacted naval warfare by targeting enemy shipping. In WWI, Germany's initial U-boat successes against British warships led to unrestricted warfare, prompting the U.S. to enter the war. Despite sinking 852,000 tons of Allied and neutral ships in April 1917, the introduction of convoys and U.S. destroyers turned the tide.
In WWII, U-boats initially achieved great success, sinking over 6,266,000 tons of shipping in 1942. Operating in groups called "wolf packs," they attacked convoys at night until radar aided escorts. Although U-boats were equipped with snorkels, which allowed them to operate virtually undetectable to radar, Allied surface and air resources overwhelmed them. By the end of WWII, 785 of 1,162 German U-boats had been destroyed.
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What types of weapons did U-boats use?
During World War I and World War II, U-boats used various weapons to attack enemy ships. The primary weapon was the self-propelled torpedo, launched from tubes. U-boats also carried deck guns, typically three- or four-inch caliber, to attack smaller or unarmed ships without wasting torpedoes. Some U-boats were modified to lay mines outside enemy harbors. During World War II, the Type VIIC U-boat had a 90-millimetre deck gun, antiaircraft guns, and five torpedo tubes. Some later German submarines even carried 150-millimetre guns.
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How did other countries try to defend themselves against U-boats?
During World War I and World War II, several strategies and technologies were employed to defend against German U-boats. These included:
- Convoy Systems Merchant vessels sailed in large, protected groups escorted by warships, which deterred U-boats from attacking and allowed escort ships to defend the merchant vessels.
- Naval and Air Support Warships such as destroyers and corvettes, as well as aircraft, were used to protect convoys. Aircraft were equipped with depth charges to attack submerged submarines.
- Radar Technology The introduction of radar helped escort ships and aircraft detect U-boats, especially when the U-boats operated on the surface at night.
- Sonar The new use of sonar allowed convoys to coordinate more effectively and provided greater protection against German U-boat tactics.
- Attacking Supply Vessels Allied forces targeted U-boats' supply vessels to disrupt their operations.
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U-boat, (âundersea boatâ), a German submarine. The destruction of enemy shipping by German U-boats was a spectacular feature of both World Wars I and II.
World War I
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 1914â18 the destructionâmore than 10,000,000 tonsâcaused by the U-boats was especially remarkable in view of the small size (less than l,000 tons), frailty, and vulnerability of the craft.
World War II
The Armistice terms of 1918 required Germany to surrender all its U-boats, and the Treaty of Versailles forbade it to possess them in the future. In 1935, however, Adolf Hitlerâs Germany repudiated the treaty and forcefully negotiated the right to build 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 Britainâs 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.
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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-boatsâ supply vessels and putting all possible shipping into convoys again proved successful. In the final phase the U-boatsâthen fitted with the snorkel (schnorkel) ventilating tube, which permitted extended underwater travel and greatly reduced the effectiveness of radarâreturned 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).