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For the sandwich, see Submarine sandwich for the patent type see Submarine patent

A submarine is a specialized watercraft that can operate underwater. Most major navies use submarines. Submarines are also used for marine and freshwater science and for work at depths too great for human divers.

Nuclear powered submarines and other large submarines are classed as ships, but are customarily referred to by their crews as "boats". The term U-Boat is sometimes used in English, this comes from the German word for submarine, 'U-Boot', itself an abbreviation for Unterseeboot. Modern attack submarines are known as fast attack subs and generally operate in the hunter-killer role. Large subs carrying strategic nuclear missiles are known as "boomers" in the United States Navy, and "bombers" in the Royal Navy.

Submarines encompass one of the largest ranges in capabilities of any vessel. They range from a small two-man vessel that can examine the sea floor for few hours; to underground subsea-level houses built in the 1950s as part of a "Sharing the Ocean" fund; to the Typhoon class, which can remain submerged for months and carry enough nuclear missiles to destroy hundreds of cities. There are a wide variety of specialized submarines: rescue submarines like the DSRV or recently rescued AS-28, or tiny one-person human powered subs intended for competitions between universities.

The word submarine was originally an adjective meaning "under the sea". That is why some firms who make diving gear but not parts for submarines, called their work "submarine engineering". "Submarine" as a noun meaning a submersible craft originated as short for "submarine boat"; older books (for example Twenty Thousand Leagues Under the Sea) always call it a "submarine boat".

Another underwater device for use in underwater exploration, salvage, and rescue is the diving bell.

Non-military submarines and submersibles

Non-military submarines are usually much smaller than military submarines. Tourist submarines work mainly in tropical resort areas or other areas with clear water and good visibility. In 1996, there were over fifty private submarines operating around the world, serving approximately two million passengers that year. Most of these submarines carried between twenty-five and fifty passengers at a time and sometimes made ten or more dives per day. In design, these submarines borrow mainly from research subs, having large portholes for passengers' viewing and often placing significant mechanical systems outside the hull to conserve interior space. Nonetheless, even aboard tourist submarines the seating can be rather cramped. They are mainly battery-powered and very slow.

As of January, 2005, the largest tourist submarine in use was the Atlantis XIV based out of Waikiki beach. The largest Atlantis-class submarine of its fleet, launched in 1994, can carry 64 passengers and 3 crew (two guides and a pilot) to depths of 150 feet (this depth set by the state) to the sea floor off the shores of the island of O'ahu in Hawai'i. There, tourists can view a great number of ocean specimens living around artificial reefs built by the Hawaiian university out of old ships, constructions of metal flotsam, and even a sunken plane, all designed to replace the reefs damaged or destroyed by human habitation of the island.


In common usage, "submarine" means a ship which operates above and below the surface, untethered. Underwater vessels with limited mobility, intended to remain in one place during most of their use, such as those used for rescue, research or salvage purposes are usually called "submersibles". Submersibles are typically transported to their area of operation by surface ships or large submarines.

In general, submersibles differ from submarines in that submersibles typically have shorter range, and operate underwater almost exclusively, having little function at the surface. Many submersibles operate on a "tether" or "umbilical", remaining connected to a tender (a submarine, surface vessel or platform).

A bathysphere or bathyscaphe is a type of submersible which lacks any self-propulsion. A predecessor of the bathysphere, the diving bell, consisted of a chamber, with an open bottom, lowered into the water

A fairly recent development, very small unmanned submersibles called "marine remotely operated vehicles" or MROVs are widely used today to work in water too deep or too dangerous for divers. For example, remotely operated vehicles (ROVs) repair offshore petroleum platforms and attach cables to sunken ships to hoist them. Such remotely operated vehicles are attached by a tether (a thick cable providing power and communications) to control center on a ship. Operators on the ship see video images sent back from the robot and may control its propellers and manipulator arm. The wreck of the Titanic was explored by such a vehicle, as well as by a manned vessel.

Military submarines

File:Los Angeles class sub.jpg
A Los Angeles class nuclear powered military submarine of the U.S. Navy

There are probably more military submarines in operation than any other type of submarine, though it is difficult to obtain exact figures because navies are secretive about their submarine fleets.

Submarines are useful to a military because they are difficult to locate and, especially when deep below the surface, also difficult to destroy. A great deal of attention in the design of a submarine is devoted to making its travel through the water as silent as possible in order to prevent its detection (sound travels underwater much more easily than does light, meaning that a submarine's sound is the distinctive feature most likely to allow its detection). If a submarine remains undetected, it is able to strike at close range.

File:USS Chicago (SSN 721) at periscope depth off Malaysia.jpg
USS Chicago at periscope depth off the coast of Malaysia. Submarines at periscope depth in clear water during the daytime are more easily detectable by aircraft that are directly overhead.

Modern submarines are usually cigar-shaped. This design, already visible on very early submarines (see below) is officially called a "teardrop hull", and was patterned after the bodies of whales. It significantly reduces the hydrodynamic drag on the sub if it's submerged, but decreases the sea-keeping capabilities and increases the drag while surfaced. Since the limitations of the propulsion systems of early military submarines forced them to operate most their time on the surface, their hulls were modeled on those of normal ships. Because of the slow submerged speeds of those subs, usually well below 10 kt, the increased drag for underwater travel was considered acceptable. Only late in World War II, when technology enhancements allowed faster and longer submerged operations and increased surveillance by enemy aircraft forced submarines to stay most of their times below the surface, did hull designs become teardrop shaped again, to reduce drag and noise.

With nuclear power, submarines can remain submerged nearly constantly, remaining underwater for months at a time. Diesel submarines, by contrast, must periodically resurface or snorkel to recharge their batteries. Some modern submarines are able to generate oxygen for their crew by electrolysis of water.

A raised tower on top of a submarine accommodates the length of the periscope and electronics masts, which can include radio, radar, electronic warfare, and other systems. In many obsolete boat-shaped classes of submarines (see history, below), the Control Room, or "Conn", was located inside this tower, which was known as the "conning tower". Since that time, however, the Conn has been located within the hull of the submarine, and the tower is more commonly called the "sail" today. In another interpretation, "conning tower" comes from the English verb "to con", which means "to navigate", indicating the presence of navigational systems in the conning tower. The Conn should not be confused with the "bridge", which is a small, open platform set into the top of the sail used for visual observation while operating on the surface. There may also be an additional closed platform below this with windows and their wipers for running under conditions of bad weather.

File:Kiosk Casabianca.jpg
Sail of the French nuclear submarine Casabianca; note the diving planes, camouflaged masts, periscope, electronic warfare masts, door and windows.
File:USS Los Angeles (SSN 688) sail showing camouflage.jpg
Closeup of USS Los Angeles' conning tower, showing diving planes, camouflaged masts, and periscope.

Modern submarines use an Inertial guidance system for navigation while submerged, but drift error build up over time is unavoidable. To counter this, the global positioning system will be occasionally used to obtain an accurate position. The periscope - a retractable tube with prisms allowing a view to the surface - is only used occasionally in modern submarines, since the range of visibility below the sea is short. The Virginia-class submarines have "photonics masts" rather than hull-penetrating optical tube periscopes. These masts still must be hoisted above the ocean surface, and employ electronic sensors for visible light, infra-red, laser range-finding, and electromagnetic surveillance.

A typical nuclear submarine can have a crew of over one hundred twenty; non-nuclear boats typically have less than half as many. Their job is one of the most difficult assignments in the navy, because they must work in isolation for long periods, without much contact with their families, since submarines normally maintain radio silence to avoid detection. Operating a submarine is dangerous, even in peacetime; many submarines have been lost in accidents (see history, below).

Types of military submarines

Non-strategic military or attack submarines may be divided in two general types: Nuclear (what the U.S. calls a fast-attack submarine; SSN) or diesel-electric (SS). Nuclear powered submarines are faster and larger, and have more firepower, carrying capacity and longer mission endurance than the diesel-electric submarine. Depending on the submarine's overall mission, the diesel-electric submarine are sometimes more suited for shallow water or littoral operations.

Every known strategic, ballistic-missile carrying submarine (SSBN) operated today is nuclear powered. In regard to tactical nuclear weapons, it is widely rumored that Israel tested nuclear-capable cruise missiles from two German-built Dolphin-class diesel submarines in May 2000 which thus may have reached operational capability today.

U.S. SSNs no longer carry nuclear-tipped Tomahawk cruise missiles as a result of nuclear arms control agreements. Some older, Trident class SSBN submarines are however scheduled to be converted to carry multiple conventional-warhead, "guided" Tomahawk missiles and thus become redesignated as an SSGN.

Attack submarines carrying missiles or torpedoes and may be nuclear, diesel-electric or air independent powered. Currently obsolete are the tactics which called for groups of specialized submarines, such as the squadrons which contained each of the Japanese Types A, B, and C, of which the first two carried scout seaplanes, and which the first type commanded; or the US Navy's hunter-killer teams. Other obsolete types include radar-picket submarines, such as USS Triton; specialized mine-layers; and those which carried attack seaplanes, such as the Japanese I-400-class.

Outside these categories may fall the many smaller midget submarines, used for sabotage, espionage and secretive transport. Five of this type were used by Japan in the attack on Pearl Harbor. North Korea's submarine fleet, estimated as the fourth-largest in the world in the 1990s, consists largely of smaller vessels. Also outside these categories fall the World War II German milchkuh submarines: submersible supply vessels.

Ballistic Missile Submarines

Comparison of different nuclear systems: left, the SNLE (Redoutable type) with the M4 missile; right, the SNLE-NG (Triomphant type) with the present M45 missile and the future M51 missile.

Ballistic missile submarines (boomers or SSBN in American slang) carry submarine-launched ballistic missiles with nuclear warheads, for attacking strategic targets such as cities or missile silos anywhere in the world. They are currently universally nuclear-powered, to provide the greatest stealth and endurance. (The first Soviet ballistic missile submarines were diesel-powered.) They played an important part in Cold War mutual deterrence, as both the United States and the Soviet Union had (or could contend to possess) the ability to conduct a retaliatory strike against the other nation in the event of a first strike. This comprised the strategy of Mutual Assured Destruction.

The U.S. has 18 Ohio-class submarines, of which 14 are Trident II SSBNs, each carrying 24 SLBMs. The American George Washington-class "boomers" were named for "famous Americans", and together with the Ethan Allen, Lafayette, James Madison, and Benjamin Franklin classes, these SSBN's comprised the "41 for Freedom." Later Ohio class submarines were named for states (recognizing the increase in striking power and importance, equivalent to battleships), with the exceptions that some of the "famous Americans" were foreigners and SSBN-730 gained the name of a Senator. The first four Ohio class vessels were equipped with Trident I, and are being converted to carry Tomahawk guided missiles instead.

For Russia, see List of NATO reporting names for ballistic missile submarines.

The British Royal Navy possess a single class of four ballistic missile submarines (what RN call "bombers", for their function), the Vanguard class. The Royal Navy's previous ballistic missile submarine class was the Resolution class which also consisted of four boats. The Resolutions, named after battleships to convey the fact they were the new capital ships, were decommissioned upon Vanguard's entering service in the 1990s.

France operates a force de frappe including a nuclear ballistic submarine fleet made up of one SSBN Redoutable class and three SSBNs of the Triomphant class. One additional SSBN of the Triomphant class is under construction.

The People's Republic of China's People's Liberation Army Navy's SLBM inventory is relatively new. China launched its first nuclear armed submarine in April 1981. The PLAN currently has 5 Hans at 5,000 tons displacement and 1 Xia at roughly 8,000 tons displacement. Both are based on Soviet designs. The Type 91 is outfitted with 6 SLBM launching tubes and the Type 92 is equipped with 12. China's SLBM program is built around its JL-1 inventory. The Chinese Navy is estimated to have 24 JL-1s. The JL-1 is basically a modified DF-21.

The PLAN plans to replace its JL-1 with an unspecified number of the longer ranged, more modern JL-2s. Deployment on the JL-2 reportedly began in late 2003.

Attack boats

File:USS Greeneville (SSN 772) in Dry Dock.jpg
The Los Angeles class attack submarine USS Greeneville in dry dock, showing typical cigar-shaped hull.

Submarines designed for the purpose of attacking merchant ships or other warships are known as "fast attacks", "hunter-killers", "fast boats", or "fleet submarines". They typically carry torpedoes for attacking naval vessels, and today carry cruise missiles for attacking either land-based targets or shipping. On American submarines, cruise missiles can be fired horizontally through a submarine's torpedo tubes, or, on newer vessels, via specially designed vertical launch tubes. The former has an effect of reducing the available torpedoes a submarine can carry, while the latter requires it to be reloaded by a submarine tender or by returning to port. The Soviet Navy also developed several types of missile attack submarines (SSGNs), which carried a heavy load of anti-surface missiles, as their primary targets were the U.S.'s primary force-projection vessel, nuclear-powered and conventional aircraft carriers.

Attack submarines can use a wide variety of propulsion systems. The majority of non-nuclear submarines use the same diesel-electric combination developed early in the 20th century, many use nuclear power, and a small but growing number use some other form of air-independent propulsion such as fuel cells or Stirling engines. All of the attack submarines of the United States use nuclear power.

All American attack submarines (that had actual names rather than just alphanumeric designators) were named for various ocean fish until the Los Angeles class, which are named for cities—with the exceptions of a few named for politicians, the Seawolf class, which received the traditional name for the first, a state name for the second and a Presidential name for the third (and last), and now the Virginia class, where the first six are named after states.

Until the 1980s, Russian attack submarines were designed around the concept of Anti-Surface Warfare so they tended to be fast and noisy. Due primarily to a U.S. sailor and communications technician that betrayed his country, John Anthony Walker, Russia learned NATO naval forces could track them quite easily and over time redesigned their submarines to operate much more quietly. The Victor III was the first class of Russian submarine to be built with this new mentality, armed with torpedoes, SUBROCs, and cruise missiles, they posed a more significant threat to NATO sea power. Today Russian Akula (Shark), Sierra, and Graney class submarines continue in design innovation and are respected as some of the finest submarines in the world.

File:Trafalgar class submarine.JPG
A Trafalgar-class submarine

Just before the 1990s, the Royal Navy consisted of diesel and nuclear powered submarines but, due to the end of the Cold War, defense cuts saw the RN submarine fleet became all-nuclear, presently consisting of the Swiftsure and Trafalgar class submarines, the latter named after the Battle of Trafalgar. The boats are armed with torpedoes, Harpoon anti-ship missiles and many are now armed with the Tomahawk cruise missile, which is fired from their torpedo tubes. The RN intends to have all of its attack submarines armed with the Tomahawk by 2008. During the Kosovo War, HMS Splendid became the first RN submarine to fire a Tomahawk in anger. The expected replacement of those classes is the Astute-class submarine, but delays have seen the expected launch of the first A class, HMS Astute, moved to 2009. Royal Navy submarines classes, including ballistic missile submarines, are letter-based; thus, all boats of the Swiftsure class begin with the letter S and the Trafalgars, the letter T. Though this has been the way with all Royal Navy submarines, they were originally designated alphanumerically, such as HMS A1 of the A-class of 1903 (built by the pioneer designer, American John P. Holland).

Today the role of all these attack boats has changed considerably since the end of the Cold War. U.S. fast boats no longer prowl the deep oceans in the hunt for the elusive Soviet, instead their job today is that of providing cruise missile support, early warning and intelligence gathering, harbor mine clearing, Special Operation Warfare team delivery, and others. The Virginia class was specifically designed for this multiple-mission capability in mind.

History of submarines

Early history of submarines and the first submersibles

A far ancestor for a submarine is probably a 17th century Ukrainian Cossack riverboat called chaika (gull) that was used underwater for reconnaissance and infiltration missions. Chaika could be easily capsized and submerged so that the crew was able to breathe underneath (like in modern diving bell) and propel the vessel by walking on the bottom of river. Special plummets (for submerging) and pipes for additional breathing have been used.

The first submersible for which there is reliable information that it was really built, is the one constructed in 1620 by Cornelius Jacobszoon Drebbel, a Dutchman in the service of James I. It was propelled by means of oars. The precise nature of the type is a matter of some controversy, some claiming it was merely a bell towed by a boat. There were two improved types, tested below the surface of the Thames between 1620 and 1624.

Though the first submersible vehicles were tools for exploring under water, it did not take long for inventors to recognize their military potential. The strategic advantages of submarines were set out by Bishop John Wilkins of Chester in Mathematicall Magick in 1648.

  1. Tis private: a man may thus go to any coast in the world invisibly, without discovery or prevented in his journey.
  2. Tis safe, from the uncertainty of Tides, and the violence of Tempests, which do never move the sea above five or six paces deep. From Pirates and Robbers which do so infest other voyages; from ice and great frost, which do so much endanger the passages towards the Poles.
  3. It may be of great advantages against a Navy of enemies, who by this may be undermined in the water and blown up.
  4. It may be of special use for the relief of any place besieged by water, to convey unto them invisible supplies; and so likewise for the surprisal of any place that is accessible by water.
  5. It may be of unspeakable benefit for submarine experiments.

The first military submarines

A cross-section sketch of Bushnell's Turtle.

The first military submarine was Turtle, a hand-powered egg-shaped device designed by the American David Bushnell, to accommodate a single man. It was the first verified submarine, capable of independent underwater operation and movement, and the first to use screws for propulsion. During the American Revolutionary War, Turtle (operated by Sgt. Ezra Lee, Continental Army) tried and failed to sink a British warship, HMS Eagle (flagship of the blockaders) in New York harbor on September 7, 1776.

In 1800, France built a Robert Fulton-designed human-powered submarine, the Nautilus, which was used in demonstrations to destroy ships with a mine. The French eventually gave up with the experiment in 1804, as did the British when they later tried the submarine. The Nautilus succeeded in sinking two warships in these demonstrations.

During the War of 1812, in 1814 Silas Halsey lost his life while using a submarine in unsuccessful attack on a British warship stationed in New London harbor.

In 1851, a Bavarian artillery corporal, Wilhelm Bauer, took a submarine called the Brandtaucher (fire-diver) to sea in Kiel Harbour. This submarine was powered by a treadwheel. It sank and the crew of 3 managed to escape with their lives. The submarine was raised in 1887 and is on display in a museum in Dresden.

Submarines in the American Civil War

File:USS Alligator 0844401.jpg
The French-designed 1862 Alligator, first submarine of the US Navy.

During the American Civil War, the Union was the first to field a submarine. The French-designed Alligator was the first U.S. Navy sub and the first to feature compressed air and an air filtration system. She was the first submarine to carry a diver lock which allowed a diver to exit to plant electrically-detonated mines on enemy ships. Initially powered by oars, she was later converted to a screw propeller. With a crew of 20, she was larger than Confederate submarines. Alligator was 47 feet (14.3 meters) long and about 4 feet (1.2 meters) in diameter. She was lost in a storm off Cape Hatteras on April 1, 1863 while uncrewed and under tow to her first combat deployment at Charleston.

The Confederate States of America fielded several human-powered submarines including CSS H. L. Hunley (named for her designer, Horace Hunley) . The first Confederate submarine was the 30-foot long Pioneer which sank a target schooner using a towed mine during tests on Lake Pontchartrain but she was not used in combat. She was scuttled after New Orleans was captured and in 1868 was sold for scrap.

CSS Hunley was used for attacking the North's ships, which were blockading the South's seaports. The submarine had a long pole in the bow, upon which was attached an explosive charge, called a spar torpedo. The sub was to sneak up to an enemy vessel, attach the explosive, move away, and then detonate. It was extremely hazardous to operate, and had no air supply other than what was contained inside the main compartment. On two occasions, the sub sank; on the first occasion half the crew died and on the second, the entire eight-man crew (including Hunley himself) drowned. On February 18, 1864 Hunley sank USS Housatonic in the Charleston Harbor, the first time a submarine successfully sank another ship, though she sank in the same engagement shortly after signaling her success. Another Confederate submarine was lost on her maiden voyage in Lake Pontchartrain; she was found washed ashore in the 1870s and is now on display at the Louisiana State Museum. Submarines did not have a major impact on the outcome of the war, but did portend their coming importance to naval warfare and increased interest in their use in naval warfare.

Developments in Submarines in the late 1800s

File:Ictineo II.jpg
A replica of Monturiol's wooden Ictineo II stands near Barcelona harbor

The first mechanically powered submarine was the peroxide driven Ictineo II, launched in 1864 by Narcís Monturiol. The 14 meter long craft was designed to carry a crew of two, dive 30 metres (96 feet), and stay underwater for seven and a half hours. When on the surface it ran on a steam engine, but underwater such an engine would quickly consume the submarine's oxygen. So Monturiol turned to chemistry to invent an engine that ran on a reaction of potassium chlorate, zinc and manganese peroxide. The beauty of this method was that the reaction which drove the screw released oxygen, which when treated was used in the hull for the crew and also fed an auxiliary steam engine that helped propel the craft under water. In spite of successful demonstrations in the Port of Barcelona, that made him a Catalan hero, he was unable to interest the hide bound naval officials of Spain, or of any other country.

In 1870, the French writer, Jules Verne, published the science fiction classic 20,000 Leagues under the Sea, which concerns the adventures of a maverick inventor in Nautilus, a submarine more advanced than any that existed at that time. The fictional story inspired inventors to build more advanced submarines.

In 1879, a Manchester curate, the Reverend George Garrett built the steam-powered Resurgam at Birkenhead. Garrett intended to demonstrate the 12m long vehicle to the British Navy at Portsmouth, but had mechanical problems, and while under tow the submarine was swamped and sank off North Wales.

The first submarine built in series, however, was human-powered. It was the submarine of the Polish inventor Stefan Drzewiecki—50 units were built in 1881 for Russian government. In 1884 the same inventor built an electric-powered submarine.

The Peral submarine in 1888

The first modern Military Submarine was built in Spain by Issac Peral (Spanish Engineer and Sailor), for the Spanish Navy. It was launched in September 8th, 1888. This is the first fully capable Submarine warship with electrical propulsion, torpedoes, and other news system. In Cadiz Bay,(Spain) June 1890 the Peral's Submarine launch the first torpedo under sea. This submarine displays the lines of an Albacore hull and a small conning tower, along with a cruciform tail similar to most current submarines. Despite the success of the trials, which included the first firing of a torpedo by a submarine, the Spanish Navy scrapped the project.

[Today this submarine is showed in Cartagena (Spain)]

Many more submarines were built subsequently by various inventors, but they were not to become effective weapons until the 20th century.

Late 1800s to World War I

File:USS Plunger (SS-2).jpg
USS Plunger, launched in 1902

The turn of century era marked a pivotal time in the development of submarines, with a number of important technologies making their debut, as well as the widespread adoption and fielding of submarines by a number of nations. Diesel electric propulsion would become the dominant power system and things such as the periscope would become standardized. Large numbers of experiments were done by countries on effective tactics and weapons for submarines, all of which would culminate in them making a large impact on coming World War I.

In 1895, the Irish inventor John Philip Holland designed submarines that, for the first time, made use of internal combustion engine power on the surface and electric battery power for submerged operations. In 1902, Holland received Template:US patent. Some of his vessels were purchased by the United States, the United Kingdom, the Imperial Russian Navy, and Japan, and commissioned into their navies around 1900. The US Navy commissioned its first submarine, the USS Holland in 1900, and the Imperial Japanese Navy purchased five similar designs in 1904.

The 1900 French submarine Narval

Commissionned in June 1900, the French steam and electric submarine Narval introduced the classic twin-hull design, with an inner hull inside an outer hull. France was "undoubtedly the first navy to have an effective submarine force" (Conway Marine "Steam, Steel and Shellfire"). These 200 tons ships had a radius of over 100 miles on the surface, and over 10 miles underwater. The French submarine Aigette in 1904 further improved the concept by using a diesel rather than a gasoline engine for surface power.Large quantities of these submarines were built, so that seventy-six were completed before 1914.

Submarines during World War I

German submarine U9 (1910). She sank three English cruisers in a few minutes in September 1914.

The first time military submarines had significant impact on a war was in World War I. Forces such as the U-boats of Germany saw action in the First Battle of the Atlantic. The U-boats' ability to function as practical war machines relied on new tactics, their numbers, and submarine technologies such as combination diesel/electric power system that had been developed in the preceding years. More like submersible ships than the submarines of today, U-boats operated primarily on the surface using regular engines, submerging occasionally to attack under battery power. They were roughly triangular in cross-section, with a distinct keel, to control rolling while surfaced, and a distinct bow.

Interwar developments

Various new submarine designs were developed during the interwar years. Among the most notorious ones were Submarine aircraft carriers, equiped with waterproof hangar and steam catapult and which could launch and recover one or more small seaplanes. The submarine and her plane could then act as a reconnaisance unit ahead of the fleet, an essential role at a time when radar still did not exist. The first example was the British HMS M2, followed by the French Surcouf, and numerous aircraft-carrying submarines in the Imperial Japanese Navy. The 1929 Surcouf was also designed as an "underwater cruiser," intended to seek and engage in surface combat.

Submarines during World War II


Germany had the largest submarine fleet during World War II, due to the Treaty of Versailles which limited the surface navy of Germany to six battleships (of less than 10,000 tons), six cruisers and twelve destroyers. Though the Treaty was no longer in effect in the late thirties, the rebuilding of the German surface forces had only begun in earnest a year before the outbreak of World War II. Having no hope of defeating the vastly superior Royal Navy decisively in a surface battle, the German High Command immediately stopped all construction on capital surface ships save the nearly completed Bismarck class battleships and two cruisers and switched the resources to submarines, that could be built within weeks. Though it took most of 1940 to expand the production facilities and get the mass production started, more than a thousand submarines were built until the end of the war.

U-47 returns to port after sinking HMS Royal Oak in October 1939. The battlecruiser Scharnhorst is seen in the background.

Germany put submarines to devastating effect in the Second Battle of the Atlantic in World War II, such as attempting but ultimately failing to cut off Britain's supply routes by sinking more ships than Britain could replace over a prolonged period of time (Germany targeted the supply lines because Britain is a nation reliant on imports for food and industry). Although the U-boats had been updated in the intervening years, the major innovation was improved communications, facilitated with the famous Enigma cypher machine. This allowed for mass-attack tactics in what popularly became known as a "wolf pack", although the German term, Rudel (meaning pack), did not specify wolves.

After putting to sea, the U-boats operated mostly on their own trying to find convoys in areas assigned to them by the High Command. If a convoy was found, the submarine did not attack immediately, but shadowed the convoy to allow other submarines in the area to find the convoy. These were then amassed into a formidable striking force and attacked the convoy simultaneously, preferably at night while being surfaced. The convoys escorts, often not more than three to five vessels early in the war and looking for submerged submarines, were often helpless.

In the first half of the War the submarines scored spectacular successes with these tactics, but were too few to have any decisive success. In the second half Germany had enough submarines, but this was more than nullified by equally increased numbers of convoy escorts, airplanes and technical advances like radar and Huff-Duff on the allied side.

Winston Churchill wrote that the U-boat threat was the only thing that ever gave him cause to doubt the Allies' eventual victory.


Main article: Imperial Japanese Navy submarines

The Imperial Japanese Navy's I-400, the largest submarine of WWII.

Japan had by far the most varied fleet of submarines of World War II, including manned torpedoes (Kaiten), midget submarines (Ko-hyoteki, Kairyu), medium-range submarines, purpose-built supply submarines (many for use by the Army), long-range fleet submarines (many of which carried an aircraft), submarines with the highest submerged speeds of the conflict (Sentaka I-200), and submarines that could carry multiple bombers (WWII's largest submarine, the Sentoku I-400). These submarines were also equipped with the most advanced torpedo of the conflict, the oxygen-propelled Type 95 (what U.S. historian Samuel E. Morison postwar called "Long Lance").

Overall, despite their technical prowesses, Japanese submarines were relatively unsuccessful. They were often used in offensive roles against warships (per the doctrine of Alfred T. Mahan, to which all major navies adhered), which were fast, maneuverable and well-defended compared to merchant ships. In 1942, Japanese submarines managed to sink two fleet aircraft carriers, one cruiser, and a few destroyers and other warships, and damage several others, including two battleships. They were not able to sustain these results afterwards, as Allied fleets were reinforced and became better organized. By the end of the war, submarines were instead often used to transport supplies to island garrisons. During the war, Japan managed to sink about 1 million tons of merchant shipping (184 ships), compared to 1.5 million tons for Great Britain (493 ships), 4.65 million tons for the US (1,079 ships) and 14.3 million tons for Germany (2,840 ships).

Early models were not very maneuverable under water, could not dive very deep, and lacked radar. (Later in the war units that were fitted with radar were in some instances sunk due to the ability of US radar sets to detect their emissions. For example, Batfish (SS-310) sunk three such equipped submarines in the span of four days). After the end of the conflict, several of Japan's most original submarines were sent to Hawaii for inspection in "Operation Road's End" (I-400, I-401, I-201 and I-203) before being scuttled by the U.S. Navy in 1946, when the Soviets demanded access to the submarines as well.

United States

Meanwhile, the US used her submarines to attack merchant shipping (commerce raiding or guerre de course), her submarines destroying more Japanese shipping than all other weapons combined. Where Japan had the finest submarine torpedoes, the USN had perhaps the worst, the Mark XIV, with a Mark VI magnetic influence exploder and Mark V contact exploder, neither of which worked correctly for the first twenty months of the war. Senior Submarine Force commanders (including one member of the Mark XIV's design team) ignored crew complaints.

While the British and Japanese also fielded attack submarines, they were used in fleet actions where they were somewhat ineffective due to their low speeds.

The schnorchel

Diesel submarines needed air to run their engines, thus they carried very large batteries for submerged travel. These limited the speed and range of the submarines while submerged. The schnorchel (a prewar Dutch invention) was used to allow German submarines to run just under the surface, attempting to avoid detection visually and by radar. The German navy experimented with engines that would carry hydrogen peroxide to allow diesel fuel to be used while submerged, but technical difficulties made this infeasible. On the other side, the Allies experimented with a variety of detection systems, including chemical sensors to "smell" the exhaust of submarines.

Modern submarines

In the 1950s, nuclear power partially replaced diesel-electric propulsion in those nations with access to nuclear technology. Equipment was also developed to extract oxygen from sea water. These two innovations gave submarines so equipped the ability to remain submerged for weeks or months, and enabled previously impossible voyages such as USS Nautilus's crossing of the North pole beneath the Arctic ice cap in 1958. Most of the naval submarines built since that time in the United States and the Soviet Union/Russia have been powered by nuclear fission reactors. Use of nuclear power instead of fossil fuel enables submarines to travel around the world submerged and essentially hidden for months at a time. The most limiting factors in the length of time staying submerged now are food supply and willingness of the crew to remain in the space-limited submarine.

While the greater endurance and performance from nuclear reactors mean that nuclear submarines are the norm, conventional diesel-electric submarines have continued to be produced by both nuclear and non-nuclear powers. Though far less capable in overall warfighting ability, conventional submarines are cheaper to build. Historically, when running on batteries they were often quieter than nuclear submarines, though technological advances in sound dampening, isolation and cancellation have substantially eroded this former strength.

During the Cold War, the United States of America and the Soviet Union maintained large submarine fleets that engaged in cat-and-mouse games; Russia continues this tradition today. The Soviet Union suffered the loss of at least four submarines during this period: K-129 was lost in 1968 (which CIA attempted to retrieve from the ocean floor with the Howard Hughes-designed ship later named Glomar Challenger), K 8 in 1970, K -219 in 1986 (subject of the film "Hostile Waters"), and Komsomolets (the only Mike class submarine) in 1989 (which held a depth record among the military submarines—1000 m). Many other Soviet subs, such as K-19 (first Soviet nuclear submarine, and first Soviet sub at North Pole) were badly damaged by fire or radiation leaks. The United States lost two nuclear submarines during this time: USS Thresher and Scorpion, both to equipment casualties.

The United Kingdom employed nuclear-powered submarines against Argentina in 1982 during the two nations' dispute over the Falkland Islands. The sinking of the antiquated cruiser ARA General Belgrano by HMS Conqueror was the first sinking by a nuclear-powered submarine in wartime.

Major submarine incidents since 2000

Main Article: Major submarine incidents since 2000

Since submarines have been actively deployed, there have been several incidents involving submarines which were not part of major combat. Most of these incidents were during the Cold War, but some are more recent. Since the year 2000 there have been 8 major naval incidents involving submarines. There were three Russian submarine incidents, in two of which the submarines in question were lost, along with three United States submarine incidents, one Chinese incident, and one Canadian incident. In August 2005, the Russian PRIZ, an AS-28 rescue submarine was trapped by cables and/or nets off of Petropavlovsk, and saved when a British ROV cut them free in a massive international effort.

Submarine propulsion

Until the advent of nuclear marine propulsion, most 20th century submarines used batteries for running underwater and gasoline (petrol) or diesel engines on the surface and to recharge the batteries. Early boats used gasoline but this quickly gave way to diesel because of the greatly reduced flammability of diesel. The diesel-electric submarine became the standard means of propulsion. Initially the diesel or gasoline engine and the electric motor were on the same shaft which also drove a propeller with clutches between each of them. This allowed the engine to drive the electric motor as a generator to recharge the batteries and also propel the submarine if required. The clutch between the motor and the engine would be disengaged when the boat dived so that the motor could be used to turn the propeller. The motor could have more than one armature on the shaft — these would be electrically coupled in series for slow speed and parallel for high speed (known as "group down" and "group up" respectively).

In the 1930s the principle was modified for some submarines designs, particularly those of the U.S. Navy and the British U-class. The engine was no longer attached to the motor/propeller drive shaft but drove a separate generator which would drive the motors on the surface and/or recharge the batteries. This diesel-electric propulsion allowed much more flexibility, for example the submarine could travel slowly whilst the engines were running at full power to recharge the batteries as quickly as possible, reducing the time a submarine needs to stay on the surface or use its snorkels. Also it was now possible to insulate the noisy diesel engines from the pressure hull making the submarine quieter.

There were other power sources tried—oil-fired steam turbines powered the British "K" class submarines built during the First World War and in following years but these were not very successful. This was selected to give them the necessary surface speed to keep up with the British battle fleet.

Steam power was resurrected in the 1950s with the advent of the nuclear-powered steam turbine driving a generator which is now used in all large submarines. By removing the requirement for atmospheric oxygen these submarines can stay submerged indefinitely so long as food supplies remain (air is recycled and water distilled from the ocean). These vessels nevertheless always have a small battery and diesel engine/generator installation for emergency use should the reactor have to be shut down.

Anaerobic propulsion was employed by the first mechanically driven submarine Ictineo II in 1864. Ictineo's engine used a chemical mix containing a peroxide compound, that generated heat for steam propulsion while at the same time solved the problem of oxygen renovation in an hermetic container for breathing purposes. The system wasn't employed again until 1940 when the German Navy tested a system employing the same principles, the Walter turbine, on the experimental V-80 submarine and later on the naval U-791 submarine. At the end of the Second World War the British and Russians experimented with hydrogen peroxide/kerosene (paraffin) engines which could be used both above and below the surface. The results were not encouraging enough for this technique to be adopted at the time, although the Russians deployed a class of submarines with this engine type code named Quebec by NATO, they were considered a failure. Today several navies, notably Sweden now use air-independent propulsion boats which substitute liquid oxygen for hydrogen peroxide.

Most small modern commercial submarines which are not expected to operate independently just use batteries which can be recharged by a mother-ship following every dive.

Towards the end of the 20th century, some submarines began to be fitted with pump-jet propulsors instead of propellers. Although these are heavier, more expensive, and often less efficient than a propeller, they are significantly quieter, giving submarine commanders an important tactical advantage.

A further possible propulsion system for submarines is the magnetohydrodynamic drive, or "caterpillar drive", which has no moving parts. It was popularized in the movie version of The Hunt for Red October, written by Tom Clancy, which portrayed it as a virtually silent system. (In the book, a form of propulsor was used rather than an MHD.) Although some experimental surface ships have been built with this propulsion system, speeds have not been as high as those hoped. In addition, the great noise created by the formation of bubbles, and the higher power settings a submarine's reactor would need compared to a propulsor, mean that it is unlikely to be considered for any military purpose.

Submarine movies

Main article: Submarine film

A special genre of submarine movies has developed. Submarines are popular subjects for films due to the danger, drama and claustrophobia of being on a submarine, and the suspense of the cat-and-mouse game of submarine or anti-submarine warfare. These movies include The Hunt For Red October (based on a book), Das Boot, and U-571.

See also



Articles on specific vessels

Articles on specific submarine classes



  • "Steam, Steel and Shellfire, The steam warship 1815-1905", Conway's History of the Ship ISBN 0785814132

External links

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