U-boat codenamned Undersea Boat is the anglicized version of the German word U-Boot [ˈuːboːt] ( listen), a shortening of Unterseeboot, which means "undersea boat". While the German term refers to any submarine, the English one (in common with several other languages) refers specifically to military submarines operated by Germany, particularly in World War I and World War II. Although at times they were efficient fleet weapons against enemy naval warships, 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 Canada, the British Empire and the United States to the islands of Great Britain and (during World War II) to the Soviet Union and the Allied Countries in the Mediterranean. Austro-Hungarian submarines of World War I (and before) were also known as U-boats.
World War IIEdit
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. Prime Minister Winston Churchill wrote "The only thing that really frightened me during the war was the U-boat peril."
In the early stages of the war, the U-boats were extremely effective in destroying Allied shipping, initially in the mid-Atlantic, where there was a large gap in air 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 "wolfpacks" 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 more ship-like hull design reflects the fact that these were, in fact, primarily surface vessels which had the ability to submerge when necessary. This contrasts with the cylindrical profile of modern nuclear submarines, which are more hydrodynamic underwater (where they spend the majority of their time) but less stable on the surface. Indeed, while U-boats were faster on the surface than submerged, the opposite is generally true of modern subs. 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."
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 and the east coast of the United States. With the Type XXI "Elektroboot", German designers realized the U-boat depended on submerged ability both for combat effectiveness and survival; this was the first submarine whose design favored submerged performance. The Type XXI featured a revolutionary streamlined hull design, which was the basis for the later USS Nautilus nuclear submarine. Its propulsion system featured a large battery capacity, 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. However, at some point the Allies switched to centimetric radar (unbeknownst to Germany) which rendered the radar detectors ineffective. U-boat radar systems were also developed, but many captains chose not to utilize them 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 that the schnorchel mast itself could be detected beyond visual range. 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), the use of mystery ships, 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, the highest of all German forces during the war).
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 German submarine U-110, a Type IXB, was captured in 1941 by the Royal Navy, and its Enigma machine and documents were removed. U-559 was also captured by the British in October 1942, three sailors boarded her as she was sinking, and desperately threw all the code books out of the submarine. Two of them, Able Seaman Colin Grazier and Lieutenant Francis Anthony Blair Fasson continued to throw code books out of the ship as it went under water, and went down with it. Further code books were captured by raids on weather ships. U-744 was boarded by crew from the Canadian ship HMCS Chilliwack on March 6, 1944, and codes were taken from her, but by this time in the war most of the information was known. The U-505, a Type IXC, was captured by the United States Navy in June 1944. It is presently a museum ship in Chicago at the Museum of Science and Industry.
Battle of Bell IslandEdit
Two events in the battle 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 & End of WWIIEdit
Main article: 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.
United Nazi WarEdit
The New England EvacuationEdit
- Main article: The New England Evacuation
Ports in New EnglandEdit
Invasion of Lake OntarioEdit
- Main article: Battle of Lake Ontario
Battle of the English ChannelEdit
- Main article: Battle of the English Channel
Battle of The AtlanticEdit
- Main article: Battle of the Atlanitc (United Nazi War)
The U-boats' main weapon was the torpedo, though mines and deck guns (while surfaced) 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. Early German World War II torpedoes were straight runners, as opposed to the homing and pattern-running torpedoes which were fielded 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 fail to explode altogether—sometimes bouncing harmlessly off the hull of the target ship. 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 at high latitudes fluctuations in the Earth's magnetic field. These were eventually phased out, and the depth-keeping problem was solved by early 1942.
Later in the war, Germany developed an acoustic homing torpedo, the G7/T5. 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. 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. The Germans, in-turn, countered this by introducing newer and upgraded versions of the acoustic torpedoes, like the late war G7es. However, the G7es torpedoes did not see active service.
U-boats also adopted several types of "pattern-running" torpedoes which ran straight out 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.
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