Dalībnieks:Kode/Todo/Tanks en

Soldiers from U.S. 3d Armored Cavalry Regiment provide overwatch for troops from their M1 Abrams tank in Biaj, Iraq.

A tank is a tracked armoured combat vehicle designed for front-line action, combining strong offensive and defensive capabilities. For offense the tank carries a large calibre gun and machine guns while heavy armour and good all-terrain mobility provide protection for the tank and its crew.

Tanks were first manufactured during World War I in an effort to break the deadlock of trench warfare. The British Army realised that they required a vehicle that had the mobility to reach the enemy trenches over barbed wire and rough terrain, the armour to withstand small arms fire and shrapnel from artillery and the weaponry to suppress or destroy enemy infantry, machine gun nests and pillboxes.

Today, tanks are among the most formidable and versatile weapons on the battlefield. They are valued for their ability to engage a wide range of ground targets, including enemy tanks and fortifications, as well as their shock value against infantry. In the ongoing race for battlefield supremacy, tanks and armoured tactics have undergone continuous evolution for nearly a century. Although the main battle tank is generally considered a key component of modern armies, recent thinking has challenged the need for such powerful and expensive weaponry in a period characterised by unconventional and assymetric warfare.

Tanks seldom operate alone, being organised into armoured units. Despite their apparent invulnerability, without combined arms support tanks are vulnerable to specialised anti-tank artillery and aircraft, enemy tanks, anti-tank mines, and (at short ranges) infantry. Perhaps the greatest tribute to the impact of the tank on modern warfare is the variety of methods that have been developed to destroy or neutralise them.

History

World War I: The tank is born

Video clip of World War I tanks helping the Allies with an advance in Langres, France (1918).

British World War I Mark IV tank with experimental "Tadpole Tail"

The first proposal for a tank was by the Austrian Oberleutenant Günther Burstyn who, in 1911, proposed a design for "motor artillery" (Motorengeschütz) with a turret, but his design never progressed beyond a German patent in 1912^{[nepieciešama atsauce]}.

Tank or "landship" development, originally conducted by the British 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 culminating in the Mark I tank prototype 'Mother'. The first tank to engage in battle was named "D1", a British Mark I, during the Battle of Flers-Courcellette on 15 September 1916. For further information on British World War I tank actions, see Tanks in World War I.

In contrast to World War II, Germany fielded very few tanks during WWI, 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.

Mechanical problems, poor mobility and piecemeal tactical deployment limited the military significance of the tank in World War I and the tank did not fulfill its promise of rendering trench warfare obsolete. None the less, it was clear to military thinkers on both sides that tanks would play a significant role in future conflicts.

In the inter-war period tanks underwent further mechanical development and, 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 put the theory into practice on a large scale, and it was their superior tactics, not superior weapons, that made blitzkrieg so formidable^{[nepieciešama atsauce]}. For information regarding tank development in this period, see tank development between the wars.

World War II: Blitzkrieg and combined arms

German Tiger I heavy tank of WWII captured in Tunis, 1943.

British Matilda II infantry tank advancing through Egypt as part of Operation Compass, 1941.

World War II was the first conflict where armored vehicles were critical to success on the battlefield. During the German Invasion of Poland (1939) the Germans used a combination of Panzer I (a training tank), Panzer II light tanks, and captured Czechoslovakian tanks (Panzer 35(t) and Panzer 38(t)). Early war German tanks sacrificed firepower and protection for mobility and reliability. In contrast, the French employed a defensive doctrine and sacrificed mobility for firepower and protection but had poor tank command and control systems. French tanks of WWII include the Somua S35 and Char B1. The French and British used a range of tank designs with different roles (see British tank classification). One of the more successfull British tanks of the war was the Matilda tank.

The German doctrine of blitzkrieg or "Lightning War" made use of radios in all of the tanks to provide command and control, which made them more effective tank for tank than their Allied opponents in the Battle of France, despite the Allied machines being more than a match for the panzers one-on-one. German tanks bypassed enemy strong-points and could radio for close air support to destroy them, or leave them to the infantry on foot. A related development, mechanized infantry, allowed some of the troops to keep up with the tanks and create (for the period) highly mobile combined arms forces.

By 1941, the Germans had the newer Panzer III and Panzer IV tanks with which to invade the Soviet Union in Operation Barbarossa. In an echo of the Battle of France the Soviets had several good tanks and one superb tank design, the T-34. German crews were initially shocked by the excellent all-round performance of the T-34 and the protection and firepower of the KV-1. As before, the rigid Soviet command structure and poor leadership allowed their machines to be surrounded, cut off and destroyed in detail through superior German tactics. Despite early successes, the Germans began up-gunning their Panzer IVs, and eventually built larger Panther and Tiger tanks to deal with the Soviet tank threat.

When entering WWII American mass production capacity enabled her to rapidly construct thousands of relatively cheap Sherman tanks. A compromise all round, the Sherman was reliable and formed a large part of the Anglo-American combined arms forces, but they were easily destroyed by the superior German Panther and Tiger tanks. In terms of tank warfare, large numbers allowed the Americans to overrun the German forces during the Battle of Normandy. The Sherman Firefly was introduced to improve the Sherman's firepower, but concerns about protection remained.

Tank chassis were adapted to a wide range of military jobs, including mine-clearing and combat engineering tasks. Specialised self-propelled guns were also developed: artillery, tank destroyers, and assault guns were essentially cheap, stripped down tanks carrying large calibre guns, often in a fixed hull mounting. German and Soviet assault guns, like the SU-122 had the heaviest guns mounted in vehicles, but by the end of the war a gun turret was recognised as the most effective mounting for the main gun to allow movement in a different direction from firing. Improved suspension systems were developed that allowed better cross-country performance and firing while moving. 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.

By the end of the war all forces had dramatically increased their tanks' firepower and armor; for instance, the ten ton Panzer I had only two machine guns; at war's end, the standard German medium tank, the Panzer V or Panther tank mounted a powerful, high-velocity 75 mm gun and weighed forty-five tonnes but had mobility comparable to the Panzer I.

The Cold War: Tanks in the arms race

British Centurion in service from 1946 onwards.

Polish T-55A in service from 1947 onwards.

American M48 Patton in service from 1952 onwards.

During the Cold War, the two opposing forces in Europe were the Warsaw Pact countries on the one side, and the NATO countries on the other side. The Warsaw Pact was seen by the West as having an aggressive force outnumbering the NATO forces and tank development proceeded largely as it had during WWII to maintain the balance of power. The essence of tank designs during the Cold War had been hammered out in the closing months of World War II. Large turrets, capable suspension systems, greatly improved engines, sloped armor and large caliber (100mm+) guns were all introduced to tanks during WWII. Tank design during the Cold War built on this foundation and included improvements to fire control, gun stabilisation, communications and crew comfort. Armor technology progessed in an ongoing race against improvements in anti-tank weapons, especially antitank guided missiles like the TOW.

Medium tanks of WWII gradually evolved into the Main Battle Tank of the Cold War and took over all tank roles on the battlefield. This transition happened gradually in the 1950s, as it was realized that medium tanks could carry guns (such as the US 90 mm, Soviet 100 mm, and the excellent British L7 105 mm) that could penetrate any practical thickness of armor plate at long range. The WWII concept of heavy tanks, armed with the most powerful guns and heaviest armor became obsolete, since they were just as vulnerable as other vehicles to the new medium tank guns. Likewise, WWII had shown that lightly-armed, lightly-armored tanks were of little value in most roles; speed was not a substitute for armor and firepower.

The main battle tank (MBT) thus took on the role the British had once called the 'Universal tank', filling all battlefield tank roles. Among the classic tanks of the 1950s were the British Centurion, the Soviet T-55 series, and the US M48 series. These three basic vehicles were upgraded significantly over time and formed the bulk of the armored forces of NATO and the Warsaw Pact throughout the Cold War. Some of them remain in use in the 21st century.

Although the basic roles and traits of tanks were almost all developed by the end of WWI, the performance, firepower and protection of twenty-first century tanks has increased by an order of magnitude over the early prototypes. Tanks have evolved dramatically in response to continually changing threats and requirements and especially in response to the threat of other tanks.

The 21st century: American Operations in Iraq from 2003 onward

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 armored 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 (a role that tactics otherwise proscribe), 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.

Design

A Russian T-90, in service with India.

The three traditional factors determining a tank's effectiveness are its firepower, protection, and mobility. Also significant is shock action, the psychological effect of a tank's imposing battlefield presence on enemy soldiers.

Firepower is the ability of a tank to identify, engage, and destroy a target. Protection is the tank's ability to resist being detected, engaged, and disabled or destroyed by enemy fire. Mobility includes tactical mobility over diverse terrain on the battlefield, as well as strategic mobility, the ability of the tank to be transported by road, rail, sea, and perhaps by air, to the battlefield.

Tank design is traditionally held to be a compromise between these three factors--it is not considered possible to maximize all three. For example, increasing protection by adding armour will result in an increase in weight and therefore decrease mobility; increasing firepower by using a larger gun will decrease both mobility and protection (due to decreased armour at the front of the turret).

Tālāka informācija: Tank classification

Firepower

A US Medium Tank M4A3E8 tank fires from a prepared position during the Korean War.

A tank crew must be able to quickly identify, engage, and destroy many types of targets on the battlefield, while maintaining high mobility. To this end, they are equipped with sophisticated detection and fire-control equipment, a large gun capable of firing armour-piercing and high-explosive ammunition, and machine guns for defence against infantry, light vehicles, and aircraft.

The main weapon of any modern tank is a single large gun. Tank guns are among the largest-calibre weapons in use on land, with only a few artillery pieces being larger. Although the calibre has not changed substantially since the end of the Second World War, modern guns are technologically superior. The current common sizes are 120 mm for Western tanks and 125 mm for Eastern (Soviet and Chinese legacy) tanks. Tank guns have been able to fire many types of rounds, but their current use is commonly limited to kinetic energy (KE) penetrators and high explosive (HE) rounds. Recent Russian and Chinese designed tanks can fire missiles, as well. Smoothbore (rather than rifled) guns are the dominant type today. The British and Indian Armys are now the only ones to field main battle tanks carrying rifled guns. Bore evacuators (fume extractors) have become a common feature.

Modern tank guns are generally fitted with thermal jackets which reduce the effect of uneven temperature. For instance, if it were to rain on a tank barrel, the top would cool faster than the bottom, or a breeze on the left might cause the left side to cool faster than the right. This uneven cooling will cause the barrel to bend slightly and will affect long range accuracy.

Close-up of a hull-mounted machinegun.

Usually, tanks carry other armament for short range defence against infantry or targets where the use of the main weapon would be ineffective or wasteful. Typically, this is a 7.62 mm to 12.7 mm machine gun, mounted coaxially with the main gun. However, a couple of French tanks (such as the AMX-30 and AMX-40) carry a coaxial 20 mm with a high rate of fire, able to destroy lightly armoured vehicles. Additionally, many tanks carry a roof-mounted or commander's cupola machine gun for close-in ground or limited air defence. The .50in (12.7 mm) and 14.5 mm (.57in) machine guns commonly carried on U.S. and Russian tanks and the French Leclerc are also capable of destroying lightly-armoured vehicles at close range.

Some tanks have been adapted to specialised roles and have had unusual main armament such as flame-throwers. These specialised weapons are now usually mounted on the chassis of an armoured personnel carrier.

Fire control

Historically, the tank's main gun is generally fired by 'direct fire', in which its weapons were aimed through simple optical sights and laid onto target by hand, with windage estimated or assisted with a reticle (markings in the gun sight which are aligned to frame an object of known size, in this case a tank) to estimate the range to the target. Consequently, accuracy was limited at long range and concurrent movement and accurate shooting were largely impossible. Over time these sights were replaced with stereoscopic rangefinders, and later by laser range-finders.

Leopard 2 of the German Army.

Most modern main battle tanks in the armies of industrialised countries still utilize "direct fire", but deploy laser range-finders. However, some optical and reticle range-finders are still in use in older and less sophisticated vehicles. Modern tanks have a variety of sophisticated systems to make them more accurate. Gyroscopes are used to stabilise the main weapon; computers calculate the appropriate elevation and aim-point, taking input from sensors for wind speed, air temperature, humidity, the gun-barrel temperature, warping and wear, the speed of the target (calculated by taking at least two sightings of the target with the range-finder), and the movement of the tank. Infrared or light-amplification night vision equipment is also commonly incorporated. Laser target designators may also be used to illuminate targets for guided munitions. As a result, modern tanks can fire with reasonable accuracy while on the move.

Ammunition

Tanks traditionally fire fixed ammunition, contrasting with artillery's three piece ammunition (separate projectile, powder charge, and primer). Whereas artillery fires general service ammunition such as high explosive for general support, tanks, although capable of firing the same type of ammunition, generally fire armor-defeating projectiles such as high explosive squash head (HESH, also called high explosive plastic, or HEP), high explosive anti-tank (HEAT), and kinetic energy penetrators (KEP, or armour-piercing discarding sabot, APDS). For accuracy, projectiles are spun by gun-barrel rifling, or fin-stabilised (APFSDS, HEAT-FS, etc.).

Some tanks, including the M551 Sheridan, T-72, T-64, T-80, T-84, T-90, T-96, and PT-91, can fire ATGMs (anti-tank guided missile) through their gun barrel or from externally mounted launchers. This functionality can extend the effective combat range of the tank beyond the range afforded by conventional shells, depending on the capabilities of the ATGM system. It also provides the tank with a useful weapon against slow, low-flying airborne targets like helicopters. The United States has abandoned this concept, phasing out the M551 and M60A2, but CIS countries continue to employ gun-missile systems in their main battle tanks.

Protection

Sections of the side-skirt are swung aside on this M1 Abrams to expose the track so that a road wheel can be replaced.

Attēls:Cjtf7 m1abrams.jpg

An M1 Abrams tank on lookout. Heat haze from the turbine engine can be seen to the rear.

A tank's protection is the combination of its ability to avoid detection, to avoid being hit by enemy fire, its armour to resist the effects of enemy fire, and to sustain damage and complete its mission, or at least protect its crew.

Avoiding detection

Stationary tanks can be well-camouflaged in woodland and forested areas where there is natural cover, making detection and attack from the air more difficult. By contrast, in the open it is very hard to conceal a tank. In both cases, once a tank starts its engine or begins to move it can be detected much more easily due to the thermal signature and noise generated by its engine. The tank tracks across lands can be spotted from the air, and in the desert movement can stir up dust clouds several times the size of the tanks.

A recently-stopped stationary tank has a considerable heat signature. Indeed even if the tank itself is hidden, for example behind a hill, it is still possible for a skilled operator to detect the tank from the column of warmer air above the tank. This risk can be reduced somewhat by the use of thermal blankets which reduce the radiation of heat while the engine and tracks cool. Some camouflage nets are manufactured from unevenly distributed mix of materials with differing thermal properties, which are designed to "randomise" or at least reduce the regularity of the thermal signature of a tank.

Tanks are powered by a diesel or turbine engine of a power comparable to a diesel locomotive. From the outside a diesel powered tank smells, sounds, and feels quite like a diesel locomotive. The deep rumble of even a single tank can be heard a great distance on a quiet day, and the sharp diesel smell can be carried far downwind. When a tank stands still with engine running the land trembles around it. When moving, the vibrations are greater. The acoustic and seismic signatures of multi-fuel engines are comparable. The acoustic signature of a turbine engine is much greater: its high-pitched whine can be much more easily distinguished from other sounds, near or far.

The very large power output of modern tank engines (typically in excess of 750 kW or 1,000 hp) causes a distinct thermal signature. The unusually compact mass of metal of the tank hull dissipates heat in a fashion which marks it off sharply from other objects in the countryside. A moving tank is thus relatively easy to spot by good land-based or aerial thermal infrared scanners. One reason for the one-sided fighting during Operation Desert Storm was that tanks like the US M1 Abrams and the British Challenger had almost four times the night-time infrared scanning range of the older T-72s used by the Iraqi army. Another factor in Desert Storm was that, even when camouflaged and not moving, Iraqi tanks at night would cool at a different rate from their surroundings, making thermal detection easier.

Getting a tank to move proved to be important in the Kosovo conflict in 1999. During the initial few weeks of the conflict NATO air sorties were rather ineffective in destroying Serbian tanks. This changed in the final week of the conflict, when the Kosovo Liberation Army began to engage tanks. Although the KLA had little chance of destroying the tanks, their purpose was to get the tanks to move whereupon they could be more easily identified and destroyed by NATO air power. But even this proved ineffective, as the Serbian army had few tank losses on its side, while the KLA suffered heavy infantry losses.

Armour

Abandoning a disabled M-3 tank in training.

The main battle tank is the most heavily armoured vehicle in modern land armed corps. Its armour is designed to protect the vehicle and crew against a wide variety of threats. Commonly, protection against kinetic energy penetrators fired by other tanks is considered the most important. Tanks are also vulnerable to anti-tank missiles; anti-tank mines, larger bombs, direct artillery hits, and NBC (nuclear, bacteriological, chemical) threats, which can disable or destroy them. Tanks are especially vulnerable to overhead attack. Most modern MBTs do offer near complete protection from artillery fragmentation and lighter anti-tank weapons such as rocket propelled grenades (RPGs). The amount of armour needed to protect against all conceivable threats from all angles would be far too heavy to be practical, so when designing an MBT much effort goes into finding the right balance between protection and weight.

The typical (also cheapest) means of protection is hardened steel plate, or in some cases aluminium. The relative effectiveness of armour is expressed by comparison to rolled homogeneous armour. Since the 1970s, advanced tank designs have been protected by more complex composite armour, a sandwich of various alloys and ceramics. One of the best types of passive armour is the British-developed Chobham armour, which consists of spaced ceramic blocks contained by a resin-fabric matrix between layers of conventional armour. Prior to World War 2, the relative cheapness of riveted steel armor made this a popular construction technique. However, hits on riveted vehicles could cause the rivet to be forced loose and ricochet within the vehicle, producing casualties in the crew. Later designs used either cast-steel or welded armor as a result

Before the Second World War, several tank designers tried sloped armour on new tank designs. The most famous and successful example of this approach at the time was the T-34. Angling armour greatly increases its effectiveness against projectiles, by increasing its effective perpendicular thickness, and by increasing the chance of deflection. German tank crews were said to be horrified to find shots fired at T-34s would sometimes simply ricochet. The Germans themselves took full advantage of this concept in their Panzer V (Panther) design, although modern tanks tend now to present flat surfaces as this is necessary for modern armour designs to work (modern armour attempts to disrupt the incoming projectile, for example by shearing it into two, which works best when the incoming projectile is at a right angle to the armoured surface).

Most armoured vehicles are best-protected at the front. The thickest and best-sloped armour is on the glacis plate and the turret front. The sides have less armour, while the rear, belly and roof are least protected. Since sloping of armor reduces the interior volume of the vehicle, the front armor has a steeper slope than the sides. The rear is generally not sloped at all.

Tanks are vulnerable to specialised top-attack missile weapons and air attack, as well as specialised mines. Even light infantry anti-tank weapons can immobilise a tank by damaging its suspension or track. Many tracked military vehicles have side skirts to protect the suspension. In an emergency situation, the "Molotov cocktail" can be used to attack a tank, though this is more of an insurgent/guerrilla tactic. Because of the general vulnerability of these vehicles in close-quarters fighting (urban zones, wooded areas) it is common to accompany tanks with supporting infantry.

High explosive anti-tank (HEAT) warheads, such as those of the bazooka or Panzerfaust, were a new threat in the Second World War. These used a shaped charge, which focuses the force of an explosion into a narrow penetrating stream. Thin plates of spaced armour, steel mesh "RPG screens", or rubber skirts, caused HEAT rounds to detonate further from the main armour, greatly reducing their penetrating power (technically, it increased the "standoff distance"). There were also magnetic HEAT anti-tank mines intended to be placed manually on a vulnerable side or rear area of a tank. Mid-1940s photos of German panzers covered in anti-magnetic-mine paste and with mesh coverings over their tracks as counter-measures are common.

Some anti-tank ammunition (HESH or HEP) uses flexible explosive material which squashes against a vehicle's armour and causes dangerous spalling of material inside the tank when the charge explodes. This may kill the crew without penetrating the armour, still neutralising the tank. A layer of anti-spall material on the inside of a vehicle counters this weapon.

The Israeli Merkava takes tank design for crew protection to an extreme, using the engine and fuel tanks as secondary protection.

When the armour is defeated, the ability of the surviving crew to escape becomes an issue. The provision of escape hatches in, for instance, the bottom of the hull, as in the T-34, or the side, as in the Churchill, are necessary potential weaknesses in the armour.

Passive defenses

Most armoured vehicles carry smoke grenade launchers which can rapidly deploy a smoke screen to visually shield a withdrawal from an enemy ambush or attack. This is very rarely used offensively, since attacking through it blocks the attacker's vision and gives the enemy an early indication of impending attack. Modern smoke grenades work in the infrared as well as visible spectrum.

Some smoke grenades are designed to make a very dense cloud capable of interfering with enemy laser target designators or rangefinders as well as obscuring vision, reducing probability of a hit from visually-aimed weapons, especially low velocity weapons, such as anti-tank missiles which require the operator to keep the tank in sight for a relatively long period of time. In many MBTs, such as the French Leclerc, smoke grenade launchers are also meant to launch tear gas grenades and anti-personnel fragmentation grenades. Many Israeli tanks contain small vertical mortar tubes which can be operated from within the tank, enhancing the anti-personnel capabilities and allowing it to engage targets which are behind obstacles. This idea first appeared in German tanks during WWII and there have been proposals to equip other tanks with dual-purpose smoke/fragmentation grenade launchers that can be reloaded from the interior.

Prior to the widespread introduction of thermal imaging, the most common smoke grenade in AFV launchers was white phosphorus which created a very rapid smoke screen as well as having a very useful incendiary effect against any infantry in the burst area (e.g., infantry attempting to close with hand-placed charges or mines).

Since the advent of thermal imagers, most tanks carry a smoke grenade that contains a plastic or rubber compound whose tiny burning fragments provide better obscurant qualities against thermal imagers.

Some tanks also have smoke generators which can generate smoke continuously, rather than the instantaneous, but short duration of smoke grenades. Generally smoke generators work by injecting fuel into the exhaust, which partially burns the fuel, but leaves sufficient unburned or partially burned particles to create a dense smoke screen.

Modern tanks are increasingly being fitted with passive defensive systems such as laser warning devices, which activate an alarm if the tank is "painted" by a laser range-finder or designator.

Other passive defences include radio warning devices, which provide warning if the tank is targeted by radar systems that are commonly used to guide antitank weapons such as millimetre and other very short wave radar.

Countermeasures

Passive countermeasures, like the Russian Shtora system, attempt to jam the guidance systems of incoming guided missiles.

Explosive reactive armour, or ERA, is another major type of protection against high explosive antitank weapons, in which sections of armour explode to dissipate the focused explosive force of a shaped charge warhead. Reactive armour is attached to the outside of an MBT in small, replaceable bricks.

Active protection systems go one step further. An APS uses radar or other sensing technology to automatically react to incoming projectiles. When the system detects hostile fire, it calculates a firing solution and directs an explosive-launched counter-projectile to intercept or disrupt the incoming fire a few metres from the target.

Both types of armour are potentially dangerous for friendly infantry operating in close support.

Exposed crew

An Australian Sentinel tank during trials in 1942. Note the commander's lack of protection.

Paradoxically, a tank is usually in its safest state when the commander is in a personally unsafe position, riding in the open, head out of the turret. In this rather high position (often called 'unbuttoned'), with no personal protection save maybe a helmet and a flak jacket, the commander can see around the vehicle with no restrictions, and has the greatest chance of spotting enemy antitank operations or natural and artificial obstacles which might immobilise or slow down the tank. Also, the tank itself is less visible as it can stay lower behind obstacles.

Using periscopes and other viewing devices gives a commander much inferior field of vision and sense of the countryside. Thus, when a tank advances in hostile territory with hatches closed, the commander and the crew might be personally safer, but the tank as a whole is more at risk given the extremely reduced vision. In order to overcome this problem, improvements in onboard optical systems are ongoing.

Due to the limitations of the 'closed hatch', many World War II tank commanders of all sides fought their tanks with open hatches. Sometimes this was even standard operating procedure.

Mobility

Mobility of a tank is categorised as battlefield mobility, tactical mobility, or strategic mobility. The first is a function of its engine performance and capability of its running gear and is determined by aspects such as acceleration, speed, vertical obstacle capability and so on. This is what tankers and tank designers call 'agility'. The second is the ability of the tank to be readily transported within a theatre of operation. It depends from its operational range, what bridges it can cross, and what transport vehicles can move it. The third is its ability to be transported from one theatre of operation to other, dependent on its weight, air portability and so on.

A Leclerc crossing a gap.

T-72 Ajeya of the Indian Army fitted with reactive armour during an exercise.

A main battle tank is designed to be highly mobile and able to tackle most types of terrain. Its tracks disperse the heavy weight of the vehicle over a large area, resulting in a specific ground pressure that might be lower than a man's foot. ^{[nepieciešama atsauce]} The types of terrain that do pose a problem are usually extremely soft ground such as swamps, or rocky terrain scattered with large boulders. In "normal" terrain, a tank can be expected to travel at about 20 to 30 mph (30 to 50 km/h). The road speed may be up to 43mph (70 km/h).

The logistics of getting from point A to point B are not as simple as they appear. On paper, or during any test drive of a few hours, a single tank offers better off-road performance than any wheeled fighting vehicle. On the road the fastest tank design is not much slower than the average wheeled fighting vehicle design. In practice, the huge weight of the tank combined with the relative weakness of the track assembly makes the maximum road speed of a tank really a burst speed, which can be kept up for only a short time before there is a mechanical breakdown. Although the maximum off-road speed is lower, it cannot be kept up continuously all day long, given the variety and unpredictability of off-road terrain (with the possible exception of plains and sandy deserts).

Since tank tracks have a limited life, every opportunity is used to move tanks on wheeled tank transporters and by railway instead of under their own power. Tanks invariably end up on railcars in any country with a rail infrastructure, because no army has enough wheeled transporters to carry all its tanks. Planning for railcar loading and unloading is crucial staff work, and railway bridges and yards are prime targets for enemy forces wishing to slow a tank advance.

When moving in a country or region with no rail infrastructure and few good roads, or a place with roads riddled by mines or frequent ambushes, the average speed of advance of a tank unit in a day is comparable to a man on a horse or bicycle. Frequent halts must be planned for preventive maintenance and verifications in order to avoid breakdowns during combat. This is in addition to the tactical halts needed so the infantry or the air units can scout ahead for the presence of enemy antitank groups. The German panzers, assuming that they would face minimal opposition, broke this rule, but suffered significant attrition due to equipment failure as they sped through France and Russia.

Another mobility issue is getting the tank to the theatre of operations. Tanks, especially main battle tanks, are extremely heavy, making it very difficult to airlift them. Using sea and ground transportation is slow, making tanks problematic for rapid reaction forces.

Some tank-like vehicles use wheels instead of tracks in order to increase road speed and decrease maintenance needs. These vehicles lack the superior off-road mobility of tracked vehicles, but are considered by United States planners as more suited for rapid reaction forces due to increased strategic mobility.^{[nepieciešama atsauce]}

Water operations

For most tanks, water operations are limited to fording. The fording depth is usually limited to the height of the air intake of the engine, and to a lesser extent the driver's position. The typical fording depth for MBTs is 90-120 cm. (3-4 ft).

Deep fording

A T-90, engine snorkel erected.

However, with preparation some tanks are able to ford considerably deeper waters. The German Leopard I and Leopard II tanks can ford to a depth of several meters, when properly prepared and equipped with a snorkel. The Leopard snorkel is in fact a series of rings which can be stacked to create a long tube. This tube is then fitted to the crew commander's hatch and provides air and a possible escape route for the crew. The height of the tube is limited to around three meters.

All modern Soviet/Russian tanks are also able to perform deep fording operations, however unlike the Leopard, the Russian snorkel is only a few inches round and does not provide a crew escape path, although it is more practical and can be stored on the tank.

This type of fording requires careful preparation of the tank and the ingress and egress sites on the banks of the water obstacle. Tank crews usually have a negative reaction towards deep fording. This has influenced tactics in those countries where the psychological health of the crews or their capacity for rebellion is taken into account. However, if properly planned and executed this type of operation adds considerable scope for surprise and flexibility in water crossing operations.

Amphibious tanks

Sherman DD (Duplex Drive) amphibious tank with waterproof float screens, in 1944. The floatation screen was raised in the water and rear propellers provided forward thrust.

Some light tanks such as the PT-76 are amphibious, typically being propelled in the water by hydrojets or by their tracks. In 1969, the U.S. Army rushed the new M551 Sheridan to Vietnam. This 17 ton light tank was built with an aluminium hull, steel turret and gun (although the 152 mm gun was called a "launcher" at the time), and could swim across bodies of water. Because the U.S. Army had done away with the old heavy, medium, and light tank classifications prior to the Vietnam War, and had adopted the Main Battle Tank (MBT) system, the M551 was officially classified as an Airborne Reconnaissance Assault Vehicle. The M551 upon arrival in Vietnam began replacing the M48A3 Patton in all cavalry squadrons, leaving only the M48A3 in the U.S. Army's three armored battalions in Vietnam, the 1/77th, 1/69th, and the 2/34th Armor. However, the 11th Armored Cavalry Regiment did retain some M48s, as they were the only full regiment in country. Armor Crewmen Trainees at the U.S. Army's Armor School at Fort Knox Kentucky, at the time of the Sheridan entering service, were specifically instructed to refer to the Sheridan by its designated nomenclature. However, for nearly everyone today, civilian and military alike, the Sheridan is a "light tank." The Sheridan needed no modifications for river crossings, crewmen simply raised the cloth sides that were tucked inside rubber tubes along the hull's upper edges, raised the driver's front shield which had a acrylic glass window, the driver turned on his bilge pumps, shifted his transmission lever to water operations and the Sheridan entered the water. For newly arrived Sheridans, this might work as engineered. For "war weary" M551s, the driver's window was often "yellowed" and/or cracked as to obscure his vision, and the rubber tubes that contained the rolled up side sleeves were often cracked and/or frozen into place. The Sheridan could still cross a body of water, but like its swimming cousin, the M113 APC (Armoured Personnel Carrier, also built of aluminium) the river had to be narrow, less than 100 yards (100 m). In all cases, the bilge pumps had to be working properly, and even then by the time the Sheridan or the APC reached the other side, water would often fill the insides up to their armoured roofs, spilling through the hatches' cracks and emptying onto the earth once safely ashore. Often a fold down trim vane is erected to stop water washing over the bow of the tank and thus reducing the risk of the vehicle being swamped via the driver's hatch.

In World War II the M4 Medium tank (named Sherman by the British) was made amphibious with the addition of a rubberized canvas screen to provide additional buoyancy. It was propelled by propellers driven by the main engine. This was referred to as the Sherman DD (Duplex Drive) and was used on D-Day to provide close fire support on the beaches during the initial landings. The Sherman DD could not fire when afloat as the buoyancy screen was higher than the gun. A number swamped and sank in the operation, due to rough weather in the English Channel (with some tanks having been launched too far out), and to turning in the current to converge on a specific point on the battlefield, which allowed waves to breach over the screens. Those making it ashore, however, provided essential fire support in the first critical hours.

Power plants

An M1 Abrams engine undergoing maintenance, with the turret turned sideways to expose the engine deck.

The tank's power-plant supplies power for moving the tank and for other tank systems, such as rotating the turret or electrical power for a radio. Tanks fielded in WWI mostly used petrol (gasoline) engines as power-plants, unlike the American Holt Gas-Electric tank which was powered by both a petrol and an electric engine. In the Second World War, a mix of power-plant types were used; many were adapted from aircraft engines. As the Cold War started, tanks had almost all switched to diesel, improved multi-fuel versions of which are still common. Starting in the late 1970s, gas turbines began to appear.

The weight and type of power-plant (influenced by its transmission and drive train) largely determines how fast and mobile the tank is, but the terrain effectively limits the maximum speed of all tanks through the stress it puts on the suspension and the crew.

Multi-fuel diesels

All modern non-turbine tanks use a diesel engine because diesel fuel is less flammable and more economical than gasoline. Some Soviet tanks used the smoke of burning diesel as an advantage and could intentionally burn fuel in the exhaust to create smoke for cover. Fuel tanks are commonly placed at the rear of the tank, though in some designs, such as the Israeli Merkava, the diesel fuel tanks are placed around the crew area to provide an additional layer of protection. Fuel has often been stored in auxiliary tanks externally, or by other means such as in a small trailer towed behind the tank, able to be detached during combat.

Modern tank engines are in some cases multi-fuel engines, which can operate on diesel, petrol or similar fuels.

Gas turbines

Gas turbine engines have been used as auxiliary power units (APUs) in some tanks, and as main powerplants in Soviet/Russian T-80s and U.S. M1 Abrams. They are comparatively lighter and smaller than diesels at the same sustained power output. However, they are much less fuel efficient, especially at low revs, requiring more fuel to achieve the same combat range. Different models of M1 have addressed this problem with battery packs or secondary generators to power the tank's systems while stationary, saving fuel by reducing the need to idle the main turbine. T-80s can mount three large external fuel drums to extend their range. Russia has stopped production of the T-80 in favour of the diesel-powered T-90 (based on the T-72), while Ukraine has developed the diesel-powered T-80UD and T-84 with nearly the power of the gas-turbine tank.

Because of their lower efficiency, the thermal signature of a gas turbine is higher than a diesel engine at the same level of power output. On the other hand, the acoustic signature of a tank with a muffled gas turbine can be quieter than a piston engine–powered one. The M1A2 was nicknamed 'Whispering Death' for its quiet operation.

A turbine is theoretically more reliable and easier to maintain than a piston-based engine, since it has a simpler construction with fewer moving parts. In practice, however, those parts experience a higher wear due to their higher working speeds. The turbine blades are also very sensitive to dust and fine sand, so that in desert operations special filters have to be carefully fitted and changed several times daily. An improperly fitted filter, or a single bullet or piece of shell fragment can render the filter useless, potentially damaging the engine. Piston engines also need well-maintained filters, but they are more resilient if the filter does fail.

Like most modern diesel engines used in tanks, gas turbines are usually multi-fuel engines.

Command, control and communications

Commanding and coordinating a tank organisation in the field has always been subject to particular problems. Because of the isolation of small units, individual vehicles, and even the crewmen of a tank, special arrangements have had to be made. Armoured bulkheads, engine noise, intervening terrain, dust, and smoke, and the need to operate "hatches down" (or "buttoned up") comprise severe detriments to communications.

Internal communications

Every action of a tank's crew, movement and fire, is ordered by its commander. In some early tanks, the tank commander's task was severely hampered by having to load or fire the main armament, or both. In many small armoured fighting vehicles, even into the late twentieth century, the tank commander would relay movement orders to the driver by kicks to his shoulders and back. Most modern AFVs are equipped with an intercom, allowing all crewmen to talk to each other, and to operate the radio equipment. Some tanks have even been equipped with an external intercom on the rear, to allow co-operating infantry to talk to the crew.

German Army Leopard 2A6M (2007)

Tactical communications

In the earliest tank operations, communications between the members of an armoured company were accomplished using hand signals or handheld semaphore flags, and in some situations, by crewmen dismounting and walking to another tank. In World War One, situation reports were sent back to headquarters by releasing carrier pigeons through vision slits. Signal flares, smoke, movement, and weapon fire are all used by experienced crews to coordinate their tactics.

From the 1930s to the '50s, most nations' armoured forces became equipped with radios, but visual signals are still used to reduce radio chatter. A modern tank is usually equipped with radio equipment allowing its crew to communicate on a company or battalion radio network, and possibly to monitor a higher-level network, to coordinate with other arms of service. Company or battalion commanders' tanks usually have an additional radio. Communications on a busy network are subject to a set of formalised language rules called radio voice procedure.

Most armoured forces operate with the tank commander, and possibly other crewmen, "hatches up", for best possible situational awareness. When taking fire, or in potential NBC conditions, tank crews "button up" and only view the battlefield through vision slits or periscopes, severely reducing their ability to acquire targets and perceive hazards. Since the 1960s, a tank's commander has had progressively more sophisticated equipment for target acquisition. In a main battle tank, the commander has his own panoramic sights (with night-vision equipment), allowing him to designate one or more new targets, while the gunner engages another. More advanced systems allow the commander to take control of the turret and fire the main armament in an emergency.

Computerised advances

A recent development in AFV equipment is the increased integration of fire control, the laser range-finder, GPS data, and digital communications. U.S. tanks are fitted with digital computers which are connected into battlefield networks. These integrate known information on enemy targets and friendly units to greatly improve the tank commander's situational awareness. In addition to easing the reporting burden, these systems also allow for orders to be given complete with graphics and overlays, via the network.

Vulnerability

Despite being a powerful weapon and an impressive sight on the battlefield, the tank is vulnerable. In fact, the tank's basic effectiveness has led to massive development of anti-tank weapons and tactics. Some critics have noted that due to these developments, and the rising importance of asymmetrical warfare, tanks have become too vulnerable to be worth the considerable cost they represent.

Attacks

Infantry

Unsupported tanks are vulnerable to attacks by foot soldiers who manage to reach blind or weak spots (such as very close under the tank, or behind it). Tanks may be immobilised by explosives used against the tracks, or attacks through open hatches (see above)). To protect themselves, tanks generally operate with closely coordinated infantry support to protect them from enemy infantry.

Artillery

While tanks are mostly invulnerable to shell fragments, specialised anti-tank ammunition can make a well-positioned artillery piece deadly against opposing tanks (assuming the artillery can react quickly enough and depress low enough). Modern anti-tank artillery shells also include guided projectiles.

See also: Anti-tank guns

Mines

Anti-tank minefields and landmines in general have a capability to pierce a tank's (relatively) thin bottom armour. In rare cases, even IEDs (though of comparatively massive size) have been capable of actually destroying a modern tank.

Aircraft

Ground attack aircraft may use heavy machine guns or cannons as well as rockets or guided missiles against tanks, often aiming for the top armour, which again is (relatively) weak. Attack helicopters, exploiting high mobility and the use of terrain for protection, and carrying guided missiles, have also become a mainstay of anti-tank tactics for many militaries.

Logistics

Tanks suffer a major drawback compared to wheeled vehicles like armoured cars, being mechanically more complicated and requiring far more maintenance. This places strains on an army's logistic system which may inhibit tank operations. In addition, design features may cause problems; the WW2 Panther, for instance, had interleaved road wheels, which tended to clog in mud or snow, and required five wheels to be removed to change a single inner wheel, while other German tanks of the period had driven front sprockets, which added complexity compared to British ones which drove the rear sprockets.

Climate

Tanks can also be disabled by the weather: starter batteries, lubricants, and even engines may fail in extreme cold (during World War II campaigns in Russian winters, tanks were often kept running to prevent restart problems with frozen-solid engines). Engines and crew-members can also suffer from overheating during hot weather (partly combated in newer tanks by air-conditioning systems), or dust clogging important ducts.

Terrain

Tanks are also at a disadvantage in wooded terrain and urban combat environments, which negate the advantages of the tank's long-range firepower and its speed advantage over infantry, limit the crew's ability to detect potential threats, and can even limit the turret's ability to traverse. Some of these disadvantages have now been taken into account by special modifications for urban combat, and it should be noted urban operations create additional hazards for almost all unit types, with tanks often retaining a high survivability (especially against improvised and most man-portable weapons) by virtue of their armour.

Research and development

Current research involves making the tank invisible to radar by adapting stealth technologies originally designed for aircraft and a variety of luminosity and colour shaping technologies. Research is also ongoing in armour systems and new propulsion units.

One clear trend is the increasing number of electrical and communication systems on a tank, such as thermal imagers and higher powered radios.

Etymology

There are at least three possible explanations of the origin of the name "tank". 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 motorized 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.

See also

• Armoured warfare
• Hull-down
• Tank desant
• Armored car
• Armoured engineering vehicle
• Hobart's Funnies
• Infantry fighting vehicle
• Tankette
• Armoured fighting vehicle
• Tank classification
• List of armoured fighting vehicles
• List of main battle tanks by country

References

• Ogorkiewicz, Richard M. Technology of Tanks. Jane's Information Group, Coulsdon, Surrey, 1991. ISBN 0-7106-0595-1.
• Ogorkiewicz, Richard M. Design and Development of Armored Fighting Vehicles.
• Time Life Books editors. The Armored Fist. Time-Life Books, Alexandria Va., 1990. ISBN 0-8094-8609-1; ISBN 0-8094-8608-3; ISBN 0-8094-8704-7; ISBN 0-8094-8705-5.
• Weeks, John. Men Against Tanks: A History of Anti-Tank Warfare. Mason Charter, New York, 1975. ISBN 0-88405-130-7; ISBN 0-7153-6909-1 (British printing).
• Macksey, Ken. Tank Warfare.
• Forty, G. The world encyclopedia of Tanks. Lorenz Books, 2006.

External links

• Limits of a tanks movement (photos from a private homepage, US tanks in Iraq)
• The Armored Tank turns 90 @ gizmag.com Also shows a tank designed by Leonardo DaVinci
• Danish armour display all modern weapons in the danish army.

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