submarines. (See also anti-submarine weapons, midget submarines, sea power, and torpedoes.)

1. Design and development

Submarines during the Second World War only dived when necessary: most were designed primarily for good surface speed and endurance on diesels (see Table 1 for principal types). Submerged, typical storage batteries (recharged by diesels), powered electric motors for one hour at 8–9 knots or four days at 2 knots; but air became foul after about a day despite oxygen supplies and carbon dioxide absorption methods (French and German equipment was the best, followed by American, and later, British, equipment).

Submarines, Table 1: Some principal types

2. Warfare

Submarine strategy and tactics differed among the underwater belligerents; and objectives sometimes changed. The Samurai spirit of the Japanese demanded that their submarine arm operate against their opponents' warships; the clear aim of the Germans, on the other hand, was to destroy Allied merchant shipping, particularly those convoys around which the battle of the Atlantic raged; but submarines were also used, by both sides, as blockade runners and for delivering agents on to the opposing side's shores (see spies).

Just as in the First World War, U-boats nearly brought the UK to its knees. In 68 months about 2,000 Allied merchant ships, amounting to some 14.5 million tons, were sent to the bottom (see also UK, 9). Against that, 781 U-boats were lost—66% of the 1,170 commissioned, nearly 80% of the (approximate) 1,000 that actually operated. (Figures in this entry do not take account of midget submarines.)

At the outset, Hitler insisted on prize regulations being observed, though this did not prevent the sinking of the Athenia. Ordinary merchantmen were to be stopped and searched before being sunk; and the safety of crews had to be ensured. But the danger to U-boats from merchant ships which were armed, which attempted to ram, or which reported their position by radio, to say nothing of naval escorts, was plain, and the restrictions were lifted step by step. By August 1940 virtually no holds were barred. Then, after the Laconia affair in 1942, Dönitz directed that all efforts to rescue survivors were to cease: ‘Be severe.’

During their heyday (from 1940 to the end of 1942) U-boats were directed from shore HQ, in surface Wolfpacks, against convoys whenever possible. The exchange rate of ships destroyed to U-boats lost was then profitable at 14:1; but, when Allied anti-submarine measures began to take full effect, and when it became difficult for submarines to surface, it became unacceptably low—about 2:1 for the full year of 1943. Thereafter, U-boats continued to achieve isolated sinkings in all theatres but there was no longer any hope, despite new devices like the Schnorchel, of breaking the supply chain from the USA.

In 1939 British submarines had Axis warships, including U-boats, as priority targets. They were generally disposed along lines of individual patrol areas where, instead of chasing their prey, they waited, submerged, for it to come within range. However later, in the Aegean, the eastern part of the Mediterranean, and in South-East Asia, they were often given roaming commissions, to attack anything found, together with covert tasks such as landing agents. The ‘U’-class 10th Flotilla, operating under extreme difficulty from Malta during the siege of the island, demonstrated the effect of submarine warfare on a land battle. The havoc wreaked on Afrika Korps supply lines during the Western Desert campaigns caused Lt-General Fritz Bayerlein, Rommel's chief of staff, to admit: ‘We should have taken Alexandria and reached the Suez canal if it had not been for the work of your submarines.’

In all theatres, British submarines sank 169 warships (35 U-boats among them) and 493 merchant vessels, but 74 were themselves sunk—33% of those available.

The US Navy's submarine force in the Pacific war was hampered until mid-1943 by defective torpedoes; but subsequently its performance was magnificent. Like the UK, Japan was dependent on its merchant fleet as imports were essential, both for the economy and the war industry, while a very substantial outward flow of troops, arms, ammunition, aircraft, and food was needed to capture and hold Pacific island territories. Thus, in December 1941, the USA resolved, despite earlier protestations, on unrestricted submarine warfare against Japan's merchant marine. This strategy demanded different tactics; and peacetime caution was abandoned by fresh, spirited commanding officers who discounted the dangers of attacking on the surface or at periscope depth. Radar and sophisticated fire-control methods came to be employed with great success while ULTRA intelligence enabled USN submarines, using their high surface speed, to intercept their targets. Submarine warfare, amounting from mid-1944 to blockade, arguably spelled the end of Japan's fighting ability. Nearly 1,300 Japanese merchant ships, as well as one battleship, eight aircraft carriers, and eleven cruisers were sunk for the loss of 52 US submarines—18% of 288 in the force.

The Japanese Navy started the war with 60 submarines and continually added widely assorted types including boats which carried aircraft. Despite superb oxygen-fuelled torpedoes their score was relatively small because the attack boats were frequently sent, as part of the battle fleet, against heavily defended naval units instead of the more vulnerable American lines of communication. However, although fewer than a score of US naval warships were sunk by Japanese submarines, more than 170 merchant ‘supply’ and transport ships were lost to them. Japanese submarine losses amounted to 128 or 64% of the 200 available, but many of these were not engaged in combat operations.

When Italy entered the war in June 1940 it had 113 submarines which, after the USSR, was the world's largest submarine fleet. At the time its submarine equipment was thought to be modern and only 32 boats had been built before 1932. They were Mussolini's great pride, but the clarity of the waters they operated in—an aircraft could spot a submarine down to a depth of 40 m. (110 ft.)—the efficiency of British anti-submarine defences, and the immediate grip the Royal Navy imposed led, despite much activity, to poor results at the start of the battle for the Mediterranean (see Table 2). Total sinkings by Italian submarines during the war amounted to six warships and half a million tons of merchant shipping for the loss of 86 of their number, or 57% of the 150 which became operational.

Submarines Table 2: Italian submarine activity, June-October 1940

Richard Compton-Hall

Bibliography

Alden, J. , The Fleet Submarine in the US Navy (Annapolis, Md., 1979).
Blair, C. , Silent Victory—The US Submarine War against Japan (New York, 1975).
Compton-Hall, R. , The Underwater War 1939–1945 (Poole, Dorset, 1982).
Friedman, N. , Submarine Design and Development (London, 1984), chs. 1–4.
Polmar, N., and and Carpenter, D. , Submarines of the Imperial Japanese Navy 1904–1945 (London, 1986).
Terraine, J. , Business in Great Waters—The U-Boat Wars 1916–1945, Part III (London, 1989).

submarine, a vessel designed to operate below the surface of the sea. Its hull must be circular in transverse section to withstand the pressure of water to which it is subject when submerged. It must be fitted with ballast tanks to which water can be admitted to destroy its positive buoyancy when it wants to dive and from which the water can be expelled by compressed air when it wants to surface. To control the depth when the submarine is under way submerged, it needs horizontal rudders, and when dived it must have a propulsion system capable of operating without a supply of air. Until the advent of nuclear power, this could only be provided by electric motors powered by batteries. The endurance of the batteries was comparatively limited. To recharge them submarine had to use its diesel engines—on steam propulsion in the case of the K-class—which meant coming to the surface or employing its schnorkel.

Lengthways, the hull of the earlier submarines was cigar shaped, but it has now been found that optimum results are attained with a teardrop design of hull. Until the advent of nuclear-powered submarines, all others were really submersibles, that is they could not remain underwater permanently, but see also underwater vehicles.

Early Submarines.

Between 1578 and 1763 some seventeen designs of submarines have been recorded, and among the early pioneers of submarine design were the Americans David Bushnell and Robert Fulton. Further impetus was given to the design of submarines by the introduction of metal to shipbuilding, and in the latter half of the 19th century American and French engineers produced a number of models. During the American Civil War (1861–5) the ‘David’ submersibles were not a success, but the H. L. Hunley of the Confederate States Navy was the first submarine ever to sink a ship when she sank the USS Housatonic with a spar torpedo, though all her crew were killed in doing so.

At the turn of the century the invention of the diesel engine, coupled with that of the electric motor and the Whitehead torpedo, enabled real progress to be made with an effective design for a submarine. Credit for the design of the first really workable one belongs to the Irish-born American J. P. Holland (1840–1914), whose designs were accepted by the US Navy. The first five submarines built in Britain were also based on his design. They displaced 105 tons on the surface and had surface and submerged speeds of 8.5 and 7 knots respectively. Their surface endurance was 800 kilometres (500 mls.) at 7 knots using petrol-driven engines. In Germany it was decided to await the perfection of the much safer diesel engine before embarking on the construction of the first of a long line of U-boats (short for Unterseeboot) which were to play such an important part in the First (1914–18) and Second (1939–45) World Wars.

The Submarine in Two World Wars.

In 1914 there were some 400 submarines distributed among sixteen navies, of which Britain and France accounted for about half the total. Britain entered the war with 74 submarines and 31 building, Germany with 33 built and 28 building, but whereas most of the British boats were of a small, coastal type, the majority of those in the German Navy were open-sea types ranging between 550 and 850 tons displacement. During the war both sides built a number of submarines of varying types which included minelayers, a role for which the submarine is specially suitable. German construction was far and away the largest and ranged from the coastal UB types of 125–250 tons to the cruiser types of 1,700–3,200 tons capable of crossing the Atlantic.

Though there was little change in the basic design of submarines between the two world wars, they did play a much larger part in the war than in 1914–18, and the battle of the Atlantic, in which wolfpacks of U-boats attacked Allied convoys to sever the transatlantic supply route, was a crucial one. What were new were the midget-type submarines, developed initially by the Italians, who had pioneered them during the First World War, the Japanese, and later the British and Germans, to attack warships in defended harbours which conventional submarines had little chance of penetrating. Two of the most spectacular operations were the Japanese raid on Sydney Harbour in May 1942, and the crippling of the German battleship Tirpitz in September 1943 in Trondheim, Norway. Another important development in submarine warfare came in 1944 when Germany began to fit its U-boats with schnorkels which gave them a definite advantage, but by then the battle of the Atlantic had been won.

Nuclear-Powered Submarines.

In 1948 the US Atomic Energy Commission awarded a contract to the Westinghouse Electrical Company to develop a nuclear propulsion plant suitable for installation in a submarine, and on 14 June 1952 the keel of the first nuclear-powered submarine, USS Nautilus, was laid. Its completion meant that at long last the true submarine was a reality and in 1960 another nuclear-powered submarine, the USS Triton, made a circumnavigation of just over 40,000 kilometres (30,708 mls.) in 61 days without surfacing. The nuclear reactor fitted in vessels of this type is used to generate steam in much the same way as the ordinary boiler, but with certain modifications to prevent radiation injury to the crew. Since the reactor functions without the use of oxygen, the only factor limiting the time the submarine can remain submerged is the revitalization of the air to enable the crew to breathe. This is overcome by air-purifying machinery which enables the vessel to remain submerged almost indefinitely, and the modern nuclear-powered submarine, which is armed with nuclear warheads which can be fired from below the surface, can operate submerged at or near its maximum speed of about 30 knots for as long as is operationally necessary.

With the end of the Cold War the US Navy's force of nuclear-powered submarines is having to face change to meet the requirements of the navy's future strategy which was made public in 2002. For a start, four ‘Ohio’-class submarines have been armed with cruise missiles for attacking land targets and for handling Special Forces.

The problem of the only instance of a nuclear-powered submarine firing in anger was when HMS Conqueror torpedoed the Argentine cruiser General Belgrano during the Falklands conflict in 1982. She tracked her for two days before attacking, which would have been beyond the capability of any conventional submarine.

The problem of the disposal of Britain's redundant nuclear-powered submarines has yet to be solved. Currently (2004) there are eleven tied up in two British naval dockyards. The oldest, the Dreadnought, first brought into service in 1960, has been tied up since 1983.

See also warfare at sea.

SUBMARINES

SUBMARINES. The first operating submarine was tested by the Dutch inventor Cornelis Drebbel from 1620 to 1624, but a submarine was not used in combat until 1776, when David Bushnell's one-man wooden craft, the Turtle, failed in its submerged attack on the British ship Eagle in New York harbor. Later, Robert Fulton, a famous American artist and inventor, built the Nautilus (1801) out of wood covered by iron plates. Although successful in submerged tests against wooden ships, the Nautilus failed to interest the government of France, England, or the United States. Bushnell produced another submarine for the War of 1812 against England, but his craft was unsuccessful.

During the Civil War the Confederacy undertook the construction of various submarines. Horace L. Hunley financed the building of the Pioneer (1862) by James McClintock and Baxter Watson, but it never entered combat. A second vessel was lost en route to the fighting. The first submarine to sink a ship was the hand-powered Hunley. This cigar-shaped boat was made of boiler plate and manned by a crew of nine. It took the lives of thirty-five volunteers in five trial runs and became known as the Peripatetic Coffin. On the night of 17 February 1864, it drove its spar torpedo into the Union Housatonic anchored at the entrance to Charleston harbor, South Carolina, and both vessels sank. The Union's one attempt to construct a submarine proved abortive; the main effort went into semisubmersibles and monitors.

England, France, Sweden, Russia, and Spain pursued submarine development in the ninettenth century. Modern undersea craft in America evolved from the pioneering work of John P. Holland, an Irish immigrant, and Simon Lake. Holland built six submarines (1875–1897), one of which, the Plunger, won the U.S. government's competition for a practical submarine design in 1893. It was never completed. His most famous craft, the fifty-three-foot Holland, was built at his own expense and became the U.S. Navy's first submarine in 1900. Lake, Holland's chief competitor, envisioned submarines mainly as salvage and exploration vehicles. Lake's company built seven submarines for Russia (1901–1906) and twenty-seven for the United States, with the first completed in 1911.

England and Germany had a delayed interest in submarines. England's first order came in 1901; the first German vessel, the 139-foot U-1, was not completed until 1905. At the outset of World War I, there were submarines

in the fleets of all the major navies. The standard submarine was about two hundred feet long and displaced several hundred tons. German U-boats sank more than five thousand merchant and fishing ships during the conflict. After the war, the U.S. Navy built a series of classes leading to the successful Gato and Balao classes of sub-marine of World War II.

Germany again used submarines to good advantage during World War II, although its attacks failed in the end because of a devastating Allied antisubmarine campaign. In the Pacific, U.S. submarines sank 1,314 naval and merchant ships (1941–1945). Two wartime developments—radar and the snorkel (breathing tubes to draw in air from just under the surface)—made a major impact on submarine combat.

After World War II, the United States was quick to adapt advanced German submarine technology. War-built submarines were converted to the improved GUPPY-configuration (1946–1962), and the world's first nuclear-powered submarine, the U.S.S. Nautilus, was launched in 1954. With a three-thousand-ton displacement and 320 feet long, the Nautilus traversed the Arctic Ocean under the ice cap, crossing the North Pole on 3 August 1958. The U.S. Navy married the advanced Albacore "tear drop" hull with a nuclear propulsion plant to produce the Skipjack (1956–1957), and later the Thresher, Sturgeon, and Los Angeles, classes of very fast submarines, capable of underwater speeds exceeding thirty knots.

The majority of U.S. nuclear submarines are primarily intended to destroy enemy submarines; the remainder are the fleet ballistic-missile submarines armed with strategic Polaris, Poseidon, or Trident missiles for use against land targets. The Navy commissioned forty-one Polaris-Poseidon submarines between 1959 and 1967. Displacing between 5,900 and 7,320 tons each, these vessels were a vital part of the U.S. nuclear deterrent force.

The submarine played a vital role in America's Cold War military strategy. Beginning with the Poseidon missile (1970), all U.S. submarines carried submarine launched ballistic missiles (SLBMs), all of which carried multiple warheads, dubbed multiple independently targeted reentry vehicles (MIRVs). The Trident carries twenty-four Trident C-4 or D-5 missiles, each loaded with eight warheads. In 1988, the United States had sixty-six hundred warheads on thirty-two submarines and the Soviet Union thirty-four hundred warheads on sixty-three submarines. Both forces were reduced under the terms of the first Strategic Arms Reduction Talks Treaty (START I). The START II agreement in 1993 downgraded the U.S. force to about seventeen hundred warheads on eighteen submarines. The accuracy of SLBMs was greatly improved with the introduction of the global positioning system (GPS). Signals emitted from satellites in orbit enable the missile's computers to calculate its position with very high precision.

BIBLIOGRAPHY

Alden, John D. The Fleet Submarine in the U.S. Navy: A Design and Construction History. Annapolis, Md.: Naval Institute Press, 1979.

Burgess, Robert F. Ships Beneath the Sea: A History of Subs and Submersibles. New York: McGraw-Hill, 1975.

Cochran, Thomas B., William M. Arkin, and Milton M. Hoenig. Nuclear Weapons Databook. Vol. 1. Cambridge, Mass.: Ballinger, 1984.

———, et al. Nuclear Weapons Databook. Vol. 4. New York: Harper and Row, Ballinger Division, 1989.

Hoyt, Edwin P. From the Turtle to the Nautilus: The Story of Submarines. Boston: Little, Brown, 1963.

Polmar, Norman. The American Submarine. Annapolis, Md.: Nautical and Aviation Publishing Company of America, 1981

———, and Jurrien Noot. Submarines of the Russian and Soviet Navies, 1718–1990. Annapolis, Md.: Naval Institute Press, 1991.

Roscoe, Theodore. United States Submarine Operations in World War II. Annapolis, Md.: United States Naval Institute, 1949.

LeoSartori

Ken W.Sayers/a. r.

See alsoAtlantic, Battle of the ; Lusitania, Sinking of the ; Merchantmen, Armed ; Missiles, Military ; "Nautilus" ; Navy, Confederate ; North Sea Mine Barrage ; Philippine Sea, Battle of the ; World War II, Navy in .

submarine naval craft capable of operating for an extended period of time underwater. Submarines are almost always warships, although a few are used for scientific, business, or other purposes (see also submersible ).

Development of the Modern Submarine

The first submarine used in combat (1776) was invented in 1773 by David Bushnell, an American. This vessel was a small, egg-shaped craft constructed of wood and operated by one man who turned a propeller. The vessel was submerged by admitting water, and it was surfaced by forcing out the water with a hand pump. Many of Bushnell's principles were later used by Robert Fulton for the construction of his Nautilus, a submarine successfully operated (1800–1801) on the Seine River and at Le Havre. On one occasion the inventor remained submerged for 6 hr, receiving air through a tube that extended to the surface. Later Fulton devised and used a spherical tank of compressed air to replenish the air in the submarine. This device, horizontal rudders, the screw to keep water out during submerged operation, and other features of Fulton's submersible vessel made it a forerunner of the modern submarine. In the U.S. Civil War the Confederates used several submersible craft, all named David, fitted with a mine at the end of a spar that protruded from the bow. In 1864 one of these craft destroyed a Union vessel in Charleston harbor but was itself lost with its crew.

The development of the modern submarine in the United States was advanced considerably by the work of John Holland and Simon Lake. One of Holland's submarines was propelled on the surface by a gasoline engine and by electric motors powered by storage batteries when submerged. The craft was 54 ft (16 m) long and had a top speed of 6 knots and a crew of six. In 1900 it became the U.S. Navy's first submarine. Holland's efforts were especially important in the development of submergence by water ballast and of horizontal rudders for diving. Lake's Argonaut, built in 1897, became the first submarine to navigate extensively in the open sea when it made (1898) a trip through heavy storms from Norfolk, Va., to New York City. However, the Argonaut was not accepted by the U.S. Navy, and it was not until several European governments had made use of Lake's talents that the U.S. government employed him.

The Submarine in the World Wars

In 1912, E-boats, the first U.S. diesel-engine submarines, were launched. They were 135 ft (41 m) long, had a crew of 23, and were the first to cross the Atlantic. Development continued, and in World War I submarines were for the first time used extensively by both sides. The Germans used 200-ton submarines (U-boats), and later they employed 2,100-ton craft armed with as many as 19 torpedoes. To halt the heavy destruction of shipping by these U-boats the Allied powers resorted to depth charges, Q-ships (armed vessels disguised as merchantmen), and escorted convoys. With the crucial additions of sonar (which uses high-frequency sound waves to find submarines through echo tracking) and radar -equipped air escorts (often carried on small aircraft carriers ) these defenses were also used in World War II.

A typical U.S. Navy submarine in World War II was a 300-ft (91-m) craft of 1,450 tons displacement and had a crew of 55. It ran on diesel engines (while surfaced) at a speed of up to 17 knots and on electric motors (while submerged) at a speed of up to 8 knots. The ship was armed with one 3-in. (7.6-cm) dual-purpose gun, several light automatic weapons, and 10 21-in. (53-cm) torpedo tubes. A periscope is an integral part of every submarine. It extends up through the water and by a mirror arrangement provides the observer below with a view of the surface of the sea. Similar in appearance but totally different in purpose is the snorkel apparatus first employed by the Germans and now in general use. It admits air but not water and, by supplying a flow of fresh air and an outlet for foul air, makes it possible for a submarine to remain submerged for as much as nine tenths of a voyage.

In World War II the Allies and neutrals lost some 4,770 ships to submarines, mostly German U-boats; Axis submarines were a significant strategic threat until late in the war. U.S. submarines sank over 550 Japanese ships. Submarines were also used to insert commandos in enemy territory and for rescue operations. The Germans and Japanese exchanged military plans, equipment, and precious metals by submarine as well.

Nuclear Submarines and Other Developments

With the advent of atomic power, the submarine underwent major changes in propulsion and striking power. In the nuclear-powered submarine an atomic reactor generates heat that drives a high-speed turbine engine. The first nuclear-powered submarine was the U.S. Nautilus, completed in 1954. Such submarines, with underwater speeds of above 30 knots, can remain submerged for almost unlimited periods of time and have circumnavigated the globe without surfacing. In 1960 the U.S.S. George Washington was the first submarine to fire a missile from a submerged position; the same year the U.S.S. Triton became the first vessel to circumnavigate the world while submerged. The development of nuclear-powered submarines capable of launching missiles without surfacing has greatly expanded the role of the submarine; its mission is no longer restricted to the destruction of ships (including other submarines), but it now also has the role of firing guided missiles (nuclear or conventional) at land targets deep inside an enemy's borders, as U.S. submarines did during the Persian Gulf War . In the 1990s South Anerican drug cartels began using diesel-powered submarinelike vessels to smuggle illegal drugs. Now built largely of fiberglass, these "submarines" travel at the surface, with most of the vessel, except for a conning tower, submerged.

Bibliography

See F. W. Lipscomb, The British Submarine (1954); A. R. Hezlet, The Submarine and Sea Power (1967); E. P. Stafford, The Far and the Deep (1967); A. Roland, Underwater Warfare in the Age of Sail (1978); D. Carpenter, Submarines of the Imperial Japanese Navy (1986); E. P. Hoyt, The Death of the U-Boats (1988).

Submarines are special purpose naval vessels that use their submerged capability for protection. A submarine must possess a hull strong enough to withstand substantial water pressure; tanks for taking on and holding water to adjust buoyancy and facilitate diving below the water's surface; and a means of underwater propulsion. Typically, submarines carry torpedoes as weapons, but some have carried ballistic missiles.

David Bushnell's human‐powered Turtle launched the first (unsuccessful) submarine attack in New York Harbor in September 1776 during the Revolutionary War. In the Civil War, Horace Hunley built the David craft for the Confederate navy, one of which sank the USS Housatonic in July 1864, in Charleston, South Carolina, sinking itself in the process. In the late nineteenth century, John Holland, an Irish immigrant and inventor from Paterson, New Jersey, privately built a series of experimental craft culminating in a gasoline‐powered submersible, Holland VI (1896). Due to its oxygen requirements, the boat's engine could only operate while it cruised on the surface, so the vessel also had an electric battery to provide submerged propulsion. Holland's design became the basis for submarines of the U.S. Navy, and the Royal Navy bought his design as well.

European technical developments paralleled U.S. efforts, especially in Germany and France. French naval theorists of the so‐called young school (jeune école) provided submerged weapons for submarines by first combining them in 1893 with the self‐propelled torpedo. In the view of most naval officers, submarines would be especially useful to defend a coast or for a relatively weak naval power to attack an enemy line of battleships. Due to their low submerged speed, most submarines operated as temporarily submersible torpedo boats, largely sailing and often attacking while surfaced.

During World War I, the submarines, and especially the German Untersee boats (U‐boats), achieved prominence. Submarine crews gained a reputation as élite personnel who endured real hardships; few survived the sinking of a submarine. The submarines of all navies had internal combustion engines (usually diesel), a periscope, and a deck gun for surface combat, as well as torpedoes or mines. Early in the war, a submerged German U‐boat torpedoed and sank three British cruisers in one day; another was responsible for the sinking of Lusitania (1915). Against Allied merchant shipping, the long‐range U‐boat came into its own, evading the larger Royal Navy, and sometimes attacking even while surfaced until deterred by the U.S. convoy system and vigorous U.S. antisubmarine efforts in 1917–18. Allied submarines, including American boats sent to Britain in 1918, focused upon attacking enemy surface ships but faced few targets due to the enemy's caution. Since the force almost succeeded in starving Britain, the Treaty of Versailles forbade German possession of U‐boats.

After World War I, the Washington Naval Arms Limitation Conference (1922) considered a complete ban on submarines. But opposition from the Italian and French governments guaranteed that submarines remained in the inventories of most navies, and they returned in Germany after 1935. Interwar developments included improved construction, more sophisticated torpedoes, better torpedo fire control systems, and even air conditioning in U.S. vessels. Submarine doctrine remained divided between those who desired to use the boats for commerce warfare, the German goal, and those who emphasized fleet reconnaissance and attacks on warships, the policy in the U.S. and Imperial Japanese navies.

World War II saw accelerated building of submarines by both the Axis and the Allied sides, with almost 2,000 vessels serving. Overwhelmingly, submarines attacked enemy merchant shipping, despite prewar doctrines emphasizing fleet operations. Their patrols succeeded in sinking over 20 million tons of shipping, one‐quarter by 300 American boats, which provided an effective naval blockade of Japan. U.S. design innovations included improved torpedoes and the addition of radar for surface operations. Changes from 1943 onward in Germany included series construction, the snorkel, an air tube for submerged diesel use, and improvements in submarine battery power and submerged speed. All postwar diesel submarine designs made use of these German innovations.

During the Cold War, submarine design incorporated nuclear weapons and propulsion, as well as improved sonar and reduced noise signatures. Nuclear weapons entered use as torpedoes, cruise missiles, and as the strategic ballistic missiles that the United States, Soviet Union, France, Britain, and the People's Republic of China added to their fleets. Ballistic missile submarines were a prominent nuclear deterrent. Nuclear propulsion, first introduced in the U.S. Navy by Adm. Hyman Rickover, gave submarines virtually unlimited range and radically more underwater capability due to their power plants' independence of air supplies. With improved range and weapons, both diesel and nuclear submarines fully realized their capabilities, emerging as a versatile branch of modern navies.
[See also Mines, Naval; Washington Naval Arms Limitation Treaty.]

Bibliography

John Moore , Jane's Pocket Book of Submarine Development, 1976.
Ulrich Gabler , Submarine Design, 1986.
Gary Weir , Building American Submarines 1914–1940, 1991.
Gary Weir , Forged in War, 1993.
Norman Friedman , U.S. Submarines Since 1945, 1995.
Norman Friedman , U.S. Submarines Through 1945, 1995.

Sarandis Papadopoulos

Submarines. Invented by the American David Bushnell in 1773 and later improved by Robert Fulton, submarines were used by the Confederates in several Civil War naval operations. It was around 1900, however, that submarines became feasible for warfare. Electricity propelled a double‐hulled, cigar‐shaped boat; compressed air forced ballast out of tanks between the hulls to permit surfacing; and the torpedo served as the main armament. Navies originally intended to use the submarine to scout and screen for the battle fleet.

Both world wars stimulated changes in mission and extensive improvements. German U‐boats became successful commerce raiders during World War I, but antisubmarine tactics, especially the escort of merchant‐ship convoys, eventually contained them. During World War II Germany deployed U‐boats equipped with snorkels to increase range and endurance. Wolf‐pack tactics were employed against convoys, but sophisticated antisubmarine methods—radar, sonar, and air‐sea‐ground cooperation—again thwarted German commerce raiding. Meanwhile, during the Pacific war, the United States maneuvered large fleet submarines against Japanese shipping. This effort eventually interdicted Japanese maritime communications and made a vital contribution to victory.

During the Cold War, the submarine became the most important naval vessel. The use of nuclear power to propel tear‐shaped submarines capable of launching nuclear‐armed missiles from beneath the surface provided an invulnerable weapon that became the principal instrument of nuclear deterrence in the age of mutual assured destruction. Admiral Hyman Rickover (1900–1986) emerged as a major advocate of nuclear submarines. The USS Nautilus (1954), which possessed great range and endurance, presaged the Polaris submarine‐launched ballistic missiles (SLBM) of the 1960s. The Poseidon missile entered service in 1970, followed by the Trident intercontinental ballistic missile (ICBM), accurate to 4,600 miles. Meanwhile the Soviet Union achieved comparable advances as the nuclear arms competition continued to escalate.

The end of the Cold War and the consequent decline of international tension increased interest in arms control and disarmament, including nuclear submarines. The nuclear‐armed submarine, however, remained a part of the nation's military arsenal. Underwater vessels have also proven useful in scientific research and salvage operations.
See also Federal Government, Executive Branch: Department of Defense; Military, The; Nuclear Strategy; Nuclear Weapons.

Bibliography

Norman Friedman , U.S. Submarines since 1945, 1994.
Norman Friedman , U.S. Submarines through 1945, 1995.

David F. Trask

submarine Seagoing warship capable of travelling both on and under the water. Experimental submarines were used in warfare from the late 18th century. Technical advances in the late 19th century led to the adoption of underwater craft by the world's navies. Early submarines were essentially surface ships with a limited ability to remain submerged. Once underwater, they depended on battery-powered electric motors for propulsion and, with a limited air supply, were soon forced to surface. Submerging is accomplished by letting air out of internal ballast tanks; trimming underwater is done by regulating the amount of water in the ballast tanks with pumps; and surfacing is accomplished by pumping ('blowing') the water out of the tanks. The most modern submarines use nuclear power, which eliminates the need to surface while on operations.

sub·ma·rine / ˌsəbməˈrēn; ˈsəbməˌrēn/ • n. a warship with a streamlined hull designed to operate completely submerged in the sea for long periods, equipped with an internal store of air and a periscope and typically armed with torpedoes and/or missiles. ∎  a submersible craft of any kind. ∎  a submarine sandwich. • adj. existing, occurring, done, or used under the surface of the sea: submarine volcanic activity. DERIVATIVES: sub·ma·rin·er / səbˈmarənər; -məˈrēnər/ n.

submarine n. SS or SSN a warship with a streamlined hull designed to operate completely submerged in the sea for long periods, equipped with an internal store of air and a periscope and typically armed with torpedoes and/or missiles. It carries out missions of locating and destroying both surface and submerged ships, although it can perform other naval missions should the need arise. See also fleet ballistic missile submarine.

submarine adj. XVII. See SUB-, MARINE.

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