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Tank



A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility and tactical offensive and defensive capabilities. Firepower is normally provided by a large-calibre main gun in a rotating turret and secondary machine guns, while heavy armour and all-terrain mobility provide protection for the tank and its crew, allowing it to perform all primary tasks of the armoured troops on the battlefield.

Tanks were developed and first used in combat by the British during World War I as a means to break the deadlock of trench warfare. They were first deployed at the Battle of Somme in limited numbers. During construction, to conceal their true identity as weapons, they were designated as water carriers for the Mesopotamian campaign and referred to as "tanks" (as in "water tank").

Interwar developments in both design and tactics evolved during World War II, producing important concepts of armoured warfare which persist to this day and were prominently displayed during World War II. The Soviet Union introduced the T-34, one of the best tanks in service throughout the war and one of the forerunners to the main battle tank. Germany introduced blitzkrieg, a strategy which makes use of massed concentrations of tanks supported by artillery and air power to break through the enemy front and cause a complete collapse in enemy resistance.

Today, tanks seldom operate alone, as they are organized into armoured units which involve the support of infantry, who may accompany the tanks in armoured personnel carriers or infantry fighting vehicles. They are also usually accompanied by reconnaissance or ground-attack aircraft.

Due to its formidable capabilities and versatility the battle tank is generally considered a key component of modern armies. However, the prevalence of unconventional and asymmetric warfare have put into question the utility of the armoured force. Ongoing research and development attempts to equip the tank to meet the challenges of the 21st century.



History





Conception



Apart from Leonardo da Vinci's drawing of a round, tank-like armoured wagon, the first description of a tank-like vehicle and its usefulness in trench warfare is found in an H.G. Wells short story, "The Land Ironclads", in the ''Strand Magazine'', December 1903. The concept of the tank is implicit, however, in two letters published in 1833 in ''The London United Service Magazine''. In the first (January 1833) “A Constant Reader” wrote from Bombay to propose the creation of “Steam Chariots of War”: “The great forte of steam is its passiveness. Secure the boiler and the machinery from the stroke of a cannon-ball, and you might drive a steam-chariot triumphantly through a regiment. Imagine three or four of these machines driven at a galloping speed through a square of infantry; the director might be seated in perfect safety in the rear of the engine, and a body of cavalry, about fifty yards in rear, would enter the furrows ploughed by these formidable chariots, and give the coup-de-grace to the unfortunate infantry. The chariots might be armed with scythes, both in front and flank; and, if the first shock were avoided by the men opening their ranks, they might easily be made sufficiently manageable to wheel round and return on any part of the square which stood firm” (118). In the second letter (May 1833), a correspondent identified only as “C.” discussed the “Application of Steam to Engines of War,” advocating the construction of “Chariots of Iron”—“locomotive engines” covered in “proof iron plate” and capable of running “upon ordinary roads”—for use in battle (118).

Joseph Hawker is attributed as being the father of the modern tank when in 1872, Hawker took out a patent for: 'propelling a road locomotive employing endless flat linked pitch or other chains passing round the rims of the main moving wheels.' The details of his patent reveal clearly the influence his idea had on the whole concept of crawler tractors and tanks employing drive and clutch steering. In 1903, the Levavasseur project describes a caterpillar-based armoured vehicle, and some eight years later, in 1911, two practical tank designs were developed independently by Austrian engineering officer Günther Burstyn and Australian civil engineer Lancelot de Mole, but all were rejected by governmental administrations.

Burstyn designed his tank with a sprung suspension and armed with a single gun located in a revolving turret—a design quite similar to modern tanks—but he was unable to design a track that could carry the weight of the vehicle and propel it at reasonable speed. He submitted his idea of a "land torpedo boat" to the Military Technical Committee in Vienna but the idea was rejected as lacking sufficient merit; he did, however manage to patent his invention (Zl. 252 815 DRP).

Around the same time, de Mole designed "a tracked armoured vehicle" and sent his sketches to the British War Office. His idea was rejected, but after the Great War the Royal Commission awarded de Mole £965 for expenses, and in 1920 he was appointed C.B.E.Guy Hartcup, ''The War of Invention: Scientific Developments, 1914-18'', ISBN 0080335918

World War I




Landship development, originally conducted by the Royal Navy under the auspices of the Landships Committee, was sponsored by the First Lord of the Admiralty, Winston Churchill, and proceeded through a number of prototypes, importantly among them the Little Willie, designed by William Ashbee Tritton and Walter Gordon Wilson, as the first-ever completed tracked tank prototype vehicle, culminating in the Mark I tank prototype, named ''Mother''.

The descriptor "tank" is reputed to have evolved from the construction of the early batches by North British Locomotive Company in Glasgow. The order was coded as "special tanks", and ironically much of the work was undertaken in the NBLC Tank shops and the name stuck.

The first tank to engage in battle was designated ''D1'', a British Mark I, during the Battle of Flers-Courcellette on 15 September 1916.

In contrast to World War II, Germany fielded very few tanks during World War I, with only 15 of the A7V type being produced in Germany during the war. The first tank ''versus'' tank action took place on 24 April 1918 at Villers-Bretonneux, France, when three British Mark IVs met three German A7Vs. Though both sides revealed serious flaws, the British prevailed.

The French pioneered the use of a full 360º rotation turret in a tank for the first time in 1917, with the creation and deployment of the Renault FT-17 light tank, with the turret containing the tank's main armament.

Mechanical problems, poor mobility and piecemeal tactical deployment limited the military significance of the tank in World War I, and the tank did not fulfil its promise of rendering trench warfare obsolete. Nonetheless, it was clear to military thinkers on both sides that tanks would play a significant role in future conflicts.Willmott (2003), ''First World War''

Interwar period




In the interwar period tanks underwent further mechanical development. In terms of tactics, J.F.C. Fuller's doctrine of spearhead attacks with massed tank formations was the basis for work by Heinz Guderian in Germany, Percy Hobart in Britain, Adna R. Chaffee, Jr., in the U.S., Charles de Gaulle in France, and Mikhail Tukhachevsky in the USSR. All came to similar conclusions, but in the Second World War only Germany would initially put the theory into practice on a large scale, and it was their superior tactics and French blunders, not superior weapons, that made blitzkrieg so successful in May 1940. For information regarding tank development in this period, see tank development between the wars.

Germany, Italy and the Soviet Union all experimented heavily with tank warfare during their clandestine and “volunteer” involvement in the Spanish Civil War, which saw some of the earliest examples of successful mechanised combined arms—such as when Republican troops, equipped with Soviet-supplied medium tanks and supported by aircraft, eventually routed Italian troops fighting for the Nationalists in the seven-day Battle of Guadalajara in 1937.

World War II






World War II was the first conflict where armoured vehicles were critical to success on the battlefield and in this period the tank developed rapidly as a weapon system. It showed how an armoured force was capable of achieving victory in an unprecedentedly short amount of time. At the same time however, the development of effective anti-tank weaponry demonstrated that the tank was not invulnerable.

Prior to World War II the tactics and strategy of deploying tank forces underwent a revolution. Heinz Guderian, a tactical theoretician who was heavily involved in the formation of the first independent German tank force, said "Where tanks are, the front is", and this concept became a reality in World War II. Following the Invasion of Poland where tanks performed in a more traditional role in close cooperation with infantry units, in the Battle of France deep independent armoured strategic penetrations were executed by the Germans, a tactic later called blitzkrieg or 'lightning war'. Blitzkrieg made use of innovative combined arms tactics and radios in all of the tanks to provide a level of tactical flexibility and power that surpassed that of the Allied armour. The French Army, with tanks equal or superior to the German tanks in both quality and quantity, employed a linear defensive strategy in which the armoured cavalry units were made subservient to infantry as "support weapons".Deighton (1979), ''Blitzkrieg, From the rise of Hitler to the fall of Dunkirk''. In addition, they lacked radios in many of their tanks and headquarters, which limited their ability to respond to German attacks.

In accordance with blitzkrieg tactics, German tanks bypassed enemy strongpoints and could radio for close air support to destroy them, or leave them to the infantry. A related development, motorized infantry, allowed some of the troops to keep up with the tanks and create highly mobile combined arms forces. The defeat of a major military power within weeks shocked the rest of the world, resulting in an increased focus on tank and anti-tank weapon development.

The North African Campaign also provided an important battleground for tanks, as the flat, desolate terrain with relatively few obstacles or urban environments was ideal for conducting mobile armoured warfare. However, this battlefield also showed the importance of logistics, especially in an armoured force, as the principal warring armies, the German Afrika Korps and the British Eighth Army, often outpaced their supply trains in repeated attacks and counter-attacks on each other, resulting in complete stalemate. This situation would not be resolved until 1942, when during the Second Battle of El Alamein, the Afrika Korps, crippled by disruptions in their supply lines, was forced to retreat by a massively-reinforced Eighth Army, the first in a series of defeats that would eventually lead to the surrender of the remaining Axis forces in Tunisia.



The German invasion of the Soviet Union, Operation Barbarossa, started with the Soviets having a superior tank design, the T-34. A lack of preparations for the Axis surprise attack, mechanical problems, poor training of the crews and incompetent leadership caused the Soviet machines to be surrounded and destroyed in large numbers. However, interference from Adolf Hitler, the geographic scale of the conflict, the dogged resistance of the Soviet combat troops, Soviet manpower and production capability prevented a repeat of the blitzkrieg of 1940. Despite early successes against the Soviets, the Germans were forced to up-gun their Panzer IVs, and design and build larger and more expensive Panther and Tiger tanks. In doing so, the ''Wehrmacht'' denied the infantry and other support arms the production priorities that they needed to remain equal partners with the increasingly sophisticated tanks, in turn violating the principle of combined arms they had pioneered.House (1984), ''Toward Combined Arms Warfare:A Survey of 20th-Century Tactics, Doctrine, and Organization'' Soviet developments following the invasion included upgunning the T-34, development of self-propelled anti-tank guns such as the SU-152 and deployment of the IS-2 in the closing stages of the war.



When entering World War II, America's mass production capacity enabled her to rapidly construct thousands of relatively cheap M4 Medium tanks. A compromise all round, the Sherman was reliable and formed a large part of the Anglo-American ground forces, but in a tank-versus-tank battle was no match for the Panther or Tiger. Numerical and logistical superiority and the successful use of combined arms allowed the Allies to overrun the German forces during the Battle of Normandy. Upgunned versions with the 76 mm gun M1 and the 17 pounder were introduced to improve the M4's firepower, but concerns about protection remained.

Tank chassis were modified to produce flame tanks, mobile rocket artillery, and combat engineering vehicles for tasks including mine-clearing and bridging. Specialised self-propelled guns were also developed: tank destroyers and assault guns were cheap, stripped down tanks carrying heavy guns, often in a fixed hull mounting. The firepower and low cost of these vehicles made them attractive but as manufacturing techniques improved and larger turret rings made larger tank guns feasible, the gun turret was recognised as the most effective mounting for the main gun to allow movement in a different direction from firing, enhancing tactical flexibility.

The Cold War arms race



At one time, the Soviet T-72 was the most widely deployed main battle tank across the world and remains in service with the armies of several other countries.
During the Cold War, tension between the Warsaw Pact countries and North Atlantic Treaty Organisation (NATO) countries created an arms race that ensured that tank development proceeded largely as it had during World War II. The essence of tank designs during the Cold War had been hammered out in the closing stages of World War II. Large turrets, capable suspension systems, greatly improved engines, sloped armour and large-calibre (90mm and larger) guns were standard. Tank design during the Cold War built on this foundation and included improvements to fire control, gyroscopic gun stabilisation, communications (primarily radio) and crew comfort and saw the introduction of laser rangefinders and infrared night vision equipment. Armour technology progressed in an ongoing race against improvements in anti-tank weapons, especially antitank guided missiles like the TOW.

Medium tanks of World War II, evolved into the ''main battle tank'' (MBT) of the Cold War and took over the majority of tank roles on the battlefield. This gradual transition occurred in the 1950s and 1960s due to anti-tank guided missiles, sabot ammunition and high explosive anti-tank warheads. World War II had shown that the speed of a light tank was no substitute for armour and firepower and heavy tanks were as vulnerable as medium tanks to newer weapon technology, rendering them obsolete.

In a trend started in World War II, economies of scale led to serial production of progressively upgraded models of all major tanks during the Cold War. For the same reason many upgraded post-World War II tanks and their derivatives (for example, the T-55 and T-72) remain in active service around the world, and even an obsolete tank may be the most formidable weapon on battlefields in many parts of the world. Among the tanks of the 1950s were the British Centurion and Soviet T-54/55 in service from 1946, and the US M48 from 1951. These three vehicles formed the bulk of the armoured forces of NATO and the Warsaw Pact throughout much of the Cold War. Lessons learned from tanks such as the Leopard 1, M48 Patton series, Chieftain, and T-72 led to the contemporary Leopard 2, M1 Abrams, Challenger 2, C1 Ariete, T-90 and Merkava IV.

Tanks and anti-tank weapons of the Cold War era saw action in a number of proxy wars like the Korean War, Vietnam War, Indo-Pakistani War of 1971, Soviet war in Afghanistan and Arab-Israeli conflicts, culminating with the Yom Kippur War. The T-55, for example, has seen action in no fewer than 32 conflicts. In these wars the USA or NATO countries and the Soviet Union or China consistently backed opposing forces. Proxy wars were studied by Western and Soviet military analysts and provided a grim contribution to the Cold War tank development process.



Present


As of 2005, there were 1,100 M1 Abrams used by the United States Army in the course of the Iraq War, and they have proven to have an unexpectedly high level of vulnerability to roadside bombs. A relatively new type of remotely-detonated mine, the explosively formed penetrator has been used with some success against American armoured vehicles (particularly the Bradley fighting vehicle). However, with upgrades to their armour in the rear, M1s have proven invaluable in fighting insurgents in urban combat, particularly at the Battle of Fallujah, where the Marines brought in two extra brigades. Britain deployed its Challenger 2 tanks to support its operations in southern Iraq.

Research and development



Graphic representation of the cancelled US Army's XM1202 Mounted Combat System

In terms of firepower, the focus of current R&D is on increased detection capability such as thermal imagers, automated fire control systems and increased muzzle energy from the gun to improve range, accuracy and armour penetration. The most mature future gun technology is the electrothermal-chemical gun. The XM291 electrothermal-chemical tank gun has gone through successful multiple firing sequences on a modified M8 Armored Gun System chassis.

To improve tank protection, one field of research involves making the tank invisible to radar by adapting stealth technologies originally designed for aircraft. A variety of camera and display technologies attempt to improve tank camouflage or even render it invisible. Research is also ongoing in electromagnetic armour systems to disperse or deflect incoming shaped charge jets, as well as various forms of active protection systems to prevent incoming projectiles from striking the tank at all.

Mobility may be enhanced in future tanks by the use of diesel-electric or turbine-electric series hybrid drives improving fuel efficiency while reducing the size and weight of the power plant. Furthermore, advances in gas turbine technology, including the use of advanced recuperators, have allowed for reduction in engine volume and mass to less than 1 m3 and 1 metric ton, respectively, while maintaining fuel efficiency similar to that of a diesel engine.

In line with the new doctrine of Network-centric warfare, the modern battle tank shows increasing sophistication in its electronics and communication systems.

Tank design





The three traditional factors determining a tank's effectiveness in battle are its ''firepower'', ''protection'', and ''mobility''. Since the Second World War, the economics of tank production governed by the ease of manufacture and cost, and the impact of a given tank design on logistics and field maintenance capabilities, have also been accepted as important in determining how many tanks a nation can afford to field in its force structure.

No tank design has ever been fielded in significant numbers that proved to be too complex or expensive to manufacture, and made unsustainable demands on the logistics services support of the armed forces. The ''affordability of the design'' therefore takes precedence over the field performance characteristics. Nowhere was this principle illustrated better than during the Second World War when two Allied designs, the T-34 and the M4 Sherman, although both simple designs which accepted engineering compromises, were used successfully against more sophisticated designs by Germany which were harder to produce, were more expensive and demanding on overstretched logistics of the Wehrmacht. Given that a tank crew will spend most of its time occupied with maintenance of the vehicle, engineering simplicity has become the primary constraint on tank design since the Second World War despite advances in mechanical, electrical and electronics technologies.

Firepower is the ability of a tank to identify, engage, and destroy. Protection is the tank's ability to resist being detected, engaged, and disabled or destroyed. Mobility includes tactical (short range) movement over the battlefield including over rough terrain and obstacles, as well as strategic (long range) mobility, the ability of the tank to be transported by road, rail, sea, or air to the battlefield.

Tank design is a compromise; it is not possible to maximise firepower, protection and mobility simultaneously. For example, increasing protection by adding armour will result in an increase in weight and therefore decrease mobility; increasing firepower by installing a larger gun will force the designer to sacrifice speed or armour to compensate for the added weight and cost. Even in the case of the Abrams MBT which has good firepower, speed and armour, these advantages are counterbalanced by its notably thirsty engine, which ultimately reduces its range and in a larger sense its mobility.

Since World War II tank development has shifted focus from experimenting with large scale mechanical changes to the tank design to focusing on technological advances in the tank's subsystems to improve its performance. However, a number of novel designs have appeared throughout this period with mixed success, including the Soviet IT-1, the Swedish S-tank, the Israeli Merkava, and the incorporation of autoloaders to reduce the crew complement in a number of tanks.



Firepower




Rifling of a 105 mm Royal Ordnance L7 tank gun.
An M1 Abrams firing.

The main weapon of all modern tanks is a single, large-calibre gun mounted in a fully traversing turret. The typical tank gun is a smoothbore weapon capable of firing armour-piercing kinetic energy penetrators (KEP), also known as armour-piercing discarding sabot (APDS), and/or armour piercing fin stabilised discarding sabot (APFSDS) and high explosive anti-tank (HEAT) shells, and/or high explosive squash head (HESH) and/or anti-tank guided missiles (ATGM) to destroy armoured targets, as well as high explosive (HE) shells for engaging soft targets or fortifications. Canister shot may be used in close or urban combat situations where the risk of hitting friendly forces with shrapnel from HE rounds is unacceptably high.USA Today (2005), ''Tanks adapted for urban fights they once avoided''

A gyroscope is used to stabilise the main gun, allowing it to be effectively aimed and fired at the "short halt" or on the move. Modern tank guns are also commonly fitted with insulating thermal jackets to reduce gun-barrel warping caused by uneven thermal expansion, bore evacuators to minimise fumes entering the crew compartment and sometimes muzzle brakes to minimise the effect of recoil on accuracy and rate of fire.

Traditionally, target detection relied on visual identification. This was accomplished from within the tank through telescopic periscopes; occasionally however, tank commanders would open up the hatch to view the outside surroundings, which improved situational awareness but incurred the penalty of vulnerability to sniper fire, especially in jungle and urban conditions. Though several developments in target detection have taken place especially recently, these methods are still common practice.

In some cases spotting rifles were used confirm proper trajectory and range to a target. These spotting rifles were mounted co-axially to the main gun, and fired tracer ammunition ballistically matched to the gun itself. The gunner would track the movement of the tracer round in flight, and upon impact with a hard surface, it would give off a flash and a puff of smoke, after which the main gun was immediately fired. However these have been mostly superseded by laser rangefinding equipment.

Modern tanks also use sophisticated light intensification and thermal imaging equipment to improve fighting capability at night, in poor weather and in smoke. The accuracy of modern tank guns is pushed to the mechanical limit by computerised fire-control systems. A fire-control system uses a laser rangefinder to determine the range to the target, a thermocouple, anemometer and wind vane to correct for weather effects and a muzzle referencing system to correct for gun-barrel temperature, warping and wear. Two sightings of a target with the range-finder enable calculation of the target movement vector. This information is combined with the known movement of the tank and the principles of ballistics to calculate the elevation and aim point that maximises the probability of hitting the target.

Usually, tanks carry smaller calibre armament for short-range defence where fire from the main weapon would be ineffective, for example when engaging infantry, light vehicles or aircraft. A typical complement of secondary weapons is a general-purpose machine gun mounted coaxially with the main gun, and a heavier antiaircraft machine gun on the turret roof. These weapons are often modified variants of those used by infantry, and so utilise the same kinds of ammunition.

Protection





The measure of a tank's protection is the combination of its ability to avoid detection, to avoid being hit by enemy fire, its resistance to the effects of enemy fire, and its capacity to sustain damage whilst still completing its objective, or at least protecting its crew. In common with most unit types, tanks are subject to additional hazards in wooded and urban combat environments which largely negate the advantages of the tank's long-range firepower and mobility, limit the crew's detection capabilities and can restrict turret traverse. Despite these disadvantages, tanks retain high survivability against previous-generation Rocket-Propelled Grenades in all combat environments by virtue of their armour.

Almost every advanced Main Battle Tank is fitted with the British 'Chobham Armour' design; with two examples being the American 'M1 Abrams' and the German 'Leopard II'. This is the most advanced armour plating available for any tank (with the exception of the British 'Challenger II') and has been proven against a wide array of Rocket Propelled Weaponry and Explosives.

However, as effective and advanced as armour plating has become, tank survivability against newer-generation tandem-warhead anti-tank missiles is a concern for military planners.

Avoiding detection



A tank avoids detection using the doctrine of CCD: camouflage (looks the same as the surroundings), concealment (cannot be seen) and deception (looks like something else).

Working against efforts to avoid detection is the fact that a tank is a large metallic object with a distinctive, angular silhouette that emits copious heat and noise. Consequently, it is difficult to effectively camouflage a hull-up tank in the absence of some form of cover or concealment (e.g., woods). The tank becomes easier to detect when moving (typically, whenever it is in use) due to the large, distinctive auditory, vibration and thermal signature of its power plant. Tank tracks and dust clouds also betray past or present tank movement. Switched-off tanks are vulnerable to infra-red detection due to differences between the thermal conductivity and therefore heat dissipation of the metallic tank and its surroundings. At close range the tank can be detected even when powered down and fully concealed due to the column of warmer air above the tank and the smell of diesel.

Thermal blankets slow the rate of heat emission and camouflage nets use a mix of materials with differing thermal properties to operate in the infra-red as well as the visible spectrum. Camouflage attempts to break up the distinctive appearance and silhouette of a tank. Adopting a turret-down or hull-down position reduces the visible silhouette of a tank as well as providing the added protection of a position in defilade.

Armour


The ''TUSK'' for the M1 Abrams is intended to improve survivability in urban environments


To effectively protect the tank and its crew, tank armour must counter a wide variety of antitank threats. Protection against kinetic energy penetrators and high explosive anti-tank (HEAT) shells fired by other tanks is of primary importance, but tank armour also aims to protect against infantry antitank missiles, antitank mines, bombs, direct artillery hits, and (less often) nuclear, biological and chemical threats, any of which could disable or destroy a tank or its crew.

Steel armour plate was the earliest type of armour. The Germans pioneered the use of face hardened steel during World War II and the Soviets also achieved improved protection with sloped armour technology. World War II developments also spelled the eventual doom of homogeneous steel armour with the development of shaped-charge warheads, exemplified by the Panzerfaust and bazooka infantry weapons which were lethally effective, despite some early success with spaced armour. Magnetic mines led to the development of anti-magnetic paste and paint.

British tank researchers took the next step with the development of Chobham armour, or more generally composite armour, incorporating ceramics and plastics in a resin matrix between steel plates, which provided good protection against HEAT weapons. Squash head warheads led to anti-spall armour linings, and KEPs led to the inclusion of exotic materials like a matrix of depleted uranium into a composite armour configuration. Reactive armour consists of small explosive-filled metal boxes that detonate when hit by the metallic jet projected by an exploding HEAT warhead, causing their metal plates to disrupt it. Tandem warheads defeat reactive armour by causing the armour to detonate prematurely. Grenade launchers which can rapidly deploy a smoke screen and the modern Shtora soft-kill countermeasure system provide additional protection by interfering with enemy targeting and fire-control systems.

The latest generation of protective measures for tanks are active protection systems, particularly hard-kill countermeasures. The Israeli TROPHY and Iron Fist, the American Quick Kill, the Soviet Drozd, and Russian Arena systems show the potential to dramatically improve protection for tanks against missiles, RPGs and potentially KEP attacks, but concerns regarding a danger zone for nearby dismounted troops remain.

Mobility


The mobility of a tank is described by its battlefield or tactical mobility, its operational mobility, and its strategic mobility. Tactical mobility can be broken down firstly into agility, describing the tank's acceleration, braking, speed and rate of turn on various terrain, and secondly obstacle clearance: the tank's ability to travel over vertical obstacles like low walls or trenches or through water. Operational mobility is a function of manoeuvre range; but also of size and weight, and the resulting limitations on options for manoeuvre. For example, in a given sector of front, a T-80 equipped tank formation might have many more potential axes for rapid advance than a heavier M-1 Abrams equipped formation, because of the capacity limits of roads and bridges. Strategic mobility is the relative ease with which a military asset can be transported between theatres of operation and falls within the scope of military logistics. For example, a smaller tank, able to travel through rail tunnels on flatbed rolling stock, might have greater strategic mobility than a larger one.

Tank agility is a function of the weight of the tank due to its inertia while manoeuvring and its ground pressure, the power output of the installed power plant and the tank transmission and track design. In addition, rough terrain effectively limits the tank's speed through the stress it puts on the suspension and the crew. A breakthrough in this area was achieved during World War II when improved suspension systems were developed that allowed better cross-country performance and limited firing on the move. Systems like the earlier Christie or later torsion-bar suspension developed by Ferdinand Porsche dramatically improved the tank's cross-country performance and overall mobility.

A main battle tank is highly mobile and able to travel over most types of terrain due to its continuous tracks and advanced suspension. The tracks disperse the significant weight of the vehicle over a large area, resulting in a ground pressure comparable to that of a walking man. A tank can travel at approximately across flat terrain and up to on roads, but due to the mechanical strain this places on the vehicle and the logistical strain on fuel delivery and tank maintenance, these must be considered "burst" speeds that invite mechanical failure of engine and transmission systems. Consequently, wheeled tank transporters and rail infrastructure is used wherever possible for long-distance tank transport. The limitations of long-range tank mobility can be viewed in sharp contrast to that of wheeled armoured fighting vehicles. The majority of blitzkrieg operations were conducted at the pedestrian pace of , that only was achieved on the roads of France.

Water operations




In the absence of combat engineers, most tanks are limited to fording rivers. The typical fording depth for MBTs is approximately , being limited by the height of the engine air intake and driver's position. Modern Soviet tanks and the German Leopard I and Leopard II tanks can ford to a depth of 3-4 meters when properly prepared and equipped with a snorkel to supply air for the crew and engine. Tank crews usually have a negative reaction towards deep fording but it adds considerable scope for surprise and tactical flexibility in water crossing operations by opening new and unexpected avenues of attack.

Amphibious tanks are specially designed or adapted for water operations, but they are rare in modern armies, being replaced by purpose-built amphibious assault vehicles or armoured personnel carriers in amphibious assaults. Advances such as the EFA mobile bridge and MT-55 scissors bridge have also reduced the impediment to tank advance that rivers posed in World War II.

Power plants


A Leopard 2A4 with its powerplant.
The tank's power plant supplies kinetic energy to move the tank, and electric power via a generator to components such as the turret rotation motors and the tank's electronic systems. The tank power plant has evolved from predominantly petrol and adapted large-displacement aeronautical or automotive engines during World Wars I and II, through diesel engines to advanced multi-fuel diesel engines, and powerful (per unit weight) but fuel-hungry gas turbines in the T-80 and M1 Abrams.

Tank power output in context:


Command, control and communications





Commanding and coordinating tanks in the field has always been subject to particular problems, particularly in the area of communications, but in modern armies these problems have been partially alleviated by networked, integrated systems that enable communications and contribute to enhanced situational awareness.

Early communications


Armoured bulkheads, engine noise, intervening terrain, dust and smoke, and the need to operate "buttoned up" are severe detriments to communication and lead to a sense of isolation for small tank units, individual vehicles, and tank crewmen. In World War I, situation reports were sent back to headquarters by releasing carrier pigeons through vision slits and communications between vehicles was accomplished using hand signals, handheld semaphore flags (which were still in use in the Red Army in World War II) or close range verbal communication.

Modern communications and the networked battlefield


On the modern battlefield an intercom mounted in the crew helmet provides internal communications and a link to the radio network, and on some tanks an external intercom on the rear of the tank provides communication with co-operating infantry. Radio networks employ radio voice procedure to minimise confusion and "chatter".

A recent development in AFV equipment and doctrine is Network-centric warfare (US) or Network Enabled Capability (UK). This consists of the increased integration of information from the fire control system, laser rangefinder, Global Positioning System and terrain information via hardened milspec electronics and a battlefield network to display all known information on enemy targets and friendly units on a monitor in the tank. The sensor data can be sourced from nearby tanks, planes, UAVs or (in the future) infantry. This improves the tank commander's situational awareness and ability to navigate the battlefield and select and engage targets. In addition to easing the reporting burden by automatically logging all orders and actions, orders are sent via the network with text and graphical overlays.



Etymology



The word ''tank'' was first applied to the British "landships" in 1915, before they entered service, to keep their nature secret. There are at least three possible explanations of the precise origin of the term:

# One is it first arose in British factories making the hulls of the first battle tanks: workmen and possible spies were to be given the impression they were constructing mobile water containers or ''tanks'' for the British Army, hence keeping the production of a fighting vehicle secret.
# Another is the term was first used in a secret report on the new motorised weapon presented to Winston Churchill, then First Lord of the Admiralty, by British Army Lt.-Col. Ernest Swinton. From this report, three possible terms emerged: ''cistern, motor-war car,'' and ''tank.'' Apparently ''tank'' was chosen due to its linguistic simplicity.
# Perhaps the most compelling story comes from Churchill's authoritative biography. To disguise the device, drawings were marked "water carriers for Russia." When it was pointed out this might be shortened to "WCs for Russia," the drawings were changed to "water tanks for Russia." Eventually the weapon was just called a tank.

The word "tank" was adopted in most of the languages, including Russian. Some countries, however, use different names. In Germany, tank are usually refered to as "Panzer" (lit. "armour").

tank
Source: Wikipedia