Tanks
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Wikipedia-Article "Tanks"
- This article is about armoured fighting vehicles. For other meanings, see Tank (disambiguation).
A tank is a tracked armoured fighting vehicle, designed primarily to engage enemy forces by the use of direct fire. A modern main battle tank is distinguished by its high level of firepower, mobility and armour protection relative to other vehicles of its era. It can cross comparatively rough terrain at high speeds, but requires extensive fuel, maintenance, and ammunition and thus is logistically demanding. It has the heaviest armour of any vehicle on the battlefield, and carries powerful weaponry, often at least manifested in the presence of cannon that may be able to engage a wide variety of ground targets. It is among the most versatile and fearsome weapons on the battlefield, valued for its shock action against other troops and high survivability.
Tank organisations (or armoured units) are usually employed with infantry in combined arms warfare, supported by engineers, artillery, aircraft, and other support arms. If not properly protected, tanks can be vulnerable to attack by infantry, mines, artillery, and aircraft strikes. They are at a disadvantage in close terrain such as woods or built-up areas, where they lose the devastating advantage of long-range firepower, and their vulnerable suspension and top armour can be targeted by infantry anti-tank weapons.
Tanks were first used in the First World War, to break the deadlock of the trenches, and they evolved to take the role of cavalry on the battlefield. The name tank first arose in British factories making the hulls of the first battle tanks: the workmen were given the impression they were constructing tracked water containers for the British Army, hence keeping the production of a fighting vehicle secret.
Tanks and tank tactics have undergone many generations of evolution over nearly a century. Although weapons systems and armour continue to be developed, many nations have been reconsidering the need for such heavy weaponry in a period characterised by unconventional warfare.
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History
- Main article: History of the tank
World War One: the first tanks
Having already seen Rolls Royce armoured cars used by Royal Naval Air Service in 1914, and aware of schemes to create a tracked fighting vehicle, First Lord of the Admiralty Winston Churchill sponsored the Landships Committee to oversee development of this new weapon. The first successful prototype tank, nicknamed Little Willie, was tested for the British Army on September 6, 1915. Although initially termed landships by the Admiralty, the initial vehicles were colloquially referred to as water-carriers, later shortened to tanks, to preserve secrecy. The word tank was used to give the workers the impression they were constructing tracked water containers for the British army in Mesopotamia, and it was made official on December 24, 1915.
The first tank became operational when Captain H. W. Mortimore of the Royal Navy took a Mark I into action at Delville Wood during the Battle of the Somme on September 15, 1916. The French developed the Schneider CA1 working from Holt caterpillar tractors, and first used it on April 16, 1917. The first successful use of massed tanks in combat occurred at the Battle of Cambrai on November 20, 1917.
The tank would eventually make trench warfare obsolete, and the thousands of tanks fielded during the war by French and British forces made a significant contribution.
Initial results with tanks were mixed, with problems in reliability (and impatient high command) causing considerable attrition in combat. Deployment in small groups also lessened their tactical value and impact, which was still formidable during first encounters. German forces suffered from shock and lacked counter-weapons, though they did (accidentally) discover solid anti-tank shot, and the use of wider trenches to limit the British tanks' mobility.
Changing battlefield conditions and continued unreliability forced Allied tanks to continue evolving for the duration of the war, producing models such as the very long Mark V (which could navigate large obstacles, especially wide trenches, more easily than many modern AFVs).
Germany fielded a small number of tanks, mainly captured, during World War I. They only produced approximately twenty of their own design, the A7V.
Demands from infantry to have tanks close by during attacks would have pernicious effects on British tank design and tactics well into WW2.
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1920s to the end of Second World War
With the tank concept now established, several nations designed and built tanks between the two world wars. The British designs were the most advanced, due largely to their interest in an armored force during the 1930s. France and Germany did not engage in much development during the early inter War years due to the state of their economy, and the Versailles Treaty respectively. The US did little development during this period because the Cavalry branch was senior to the Armored branch and managed to absorb most of the funding earmarked for tank development. Even George S. Patton, with tank experience during WWI, transferred from the Armored branch back to the Cavalry branch during this period.
Throughout this period several classes of tanks were common, most of this development taking place in the UK. Light tanks, typically weighing ten tons or less, were used primarily for scouting and generally mounted a light gun that was useful only against other light tanks. The medium (or cruiser tanks as they were known in the UK) were somewhat heavier and focussed on long-range high-speed travel. Finally, the heavy or infantry tanks were heavily armoured and generally very slow. The overall idea was to use infantry tanks in close concert with infantry to effect a breakthrough, their heavy armour allowing them to survive with enemy antitank weapons. Once this combined force broke the enemy lines, groups of cruiser tanks would be sent through the gap, operating far behind the lines to attack supply lines and command units. This one-two punch was the basic combat philosophy of the British tank formations, and was adopted by the Germans as a major component of the blitzkrieg concept. J.F.C. Fuller's doctrine of WWI was the fount for work by all the main pioneers: Hobart in Britain, Guderian in Germany, Chaffee in the U.S., de Gaulle in France, and Tukhachevsky in the USSR. All came to roughly the same conclusions, Tukhachevsky's integration of airborne pathfinders arguably the most sophisticated; only Germany would actually put the theory to practise, and it was their superior tactics, not superior weapons, that made blitzkrieg so formidable.
There was thought put into tank-against-tank combat, but the focus was on powerful antitank guns and similar weapons, including dedicated antitank vehicles. This achieved its fullest expression in the United States, where tanks were expected to avoid enemy armour, and let dedicated tank destroyer units deal with them. Britain took the same path, and both produced light tanks in the hope that with speed, they could avoid being hit, comparing tanks to ducks. In practice these concepts proved dangerous. As the numbers of tanks on the battlefield increased, the chance of meetings grew to the point where all tanks had to be an effective antitank vehicles as well. However, tanks designed to cope only with other tanks were relatively helpless against other threats, and were not well suited for the infantry support role. Vulnerability to tank and anti-tank fire led to a rapid up-armouring and up-gunning of almost all tank designs. Tank shape, previously guided purely by considerations of obstacle clearance, now became a trade-off, with a low profile desirable for stealth and stability.
World War II saw a series of advances in tank design. Germany for example, initially fielded lightly armoured and lightly armed tanks, such as the Panzer I, which had been intended for training use only. These fast-moving tanks and other armoured vehicles were a critical element of the Blitzkrieg. However, they fared poorly in direct combat with British tanks and suffered severely against the Soviet T-34, which was superior in armour and weaponry. By the end of the war all forces had dramatically increased their tanks' firepower and armour; for instance, the Panzer I had only two machine guns, and the Panzer IV, the "heaviest" early war German design, carried a low-velocity 75mm gun and weighed under twenty tonnes. By the end of the war the standard German medium tank, the Panther, mounted a powerful, high-velocity 75mm gun and weighed forty-five tonnes.
Another major wartime advance was the introduction of radically improved suspension systems. Although this might not sound important, the quality of the suspension is the primary determinant of a tank's cross-country performance. Tanks with limited suspension travel subject their crew to massive shaking, making operation difficult, limiting speed, and making firing on the move practically impossible. Newer systems like the Christie or torsion bar suspension dramatically improved performance, allowing the late-war Panther to travel cross country at speeds that would have been difficult for earlier designs to reach on pavement.
By this time most tanks were equipped with radios (all U.S. and German, some Soviet; British radios were common, but often of indifferent quality), vastly improving the direction of units. Tank chassis were adapted to a wide range of military jobs, including mine-clearing and combat engineering tasks. All major combatant powers also developed specialised self-propelled guns: artillery, tank destroyers, and assault guns (armoured vehicles carrying large-calibre guns). German and Soviet assault guns, simpler and cheaper than tanks, had the heaviest guns in any vehicles of the war, while American and British tank destroyers were scarcely distinguishable (except in doctrine) from tanks.
Turrets, which were not previously a universal feature on tanks, were recognised as the way forward. It was appreciated that if the tank's gun was to be used to engage armoured targets then it needed to be as large and powerful as possible, making having one large gun with an all-round field of fire vital. Multiple-turreted tank designs like the Soviet T-35 were abandoned by World War II. Most tanks retained at least one hull machine gun. Even post-war, the M60 MBT had a smaller secondary turret for the commander's cupola.
The Cold War and beyond
Jeff Widener (The Associated Press)
After WWII, tank development proceeded largely as it had before, with improvements to both the medium and heavy classes. Light tanks were now limited to the reconnaissance role, and in U.S. use, airborne support as well. However, the weight limitations of air transport made a practical light tank almost impossible to build, and this class gradually disappeared over time.
But the seeds for a true transformation had already been working their way into existing designs. A combination of better suspensions and greatly improved engines allowed late-war medium tanks to outperform early-war heavies. With only slightly more armour and somewhat larger engines to compensate, mediums were suddenly protected against almost all antitank weapons, even those mounted on heavy tanks, while at the same time having the mobility of a medium tank. Many consider the turning point to be the Panther, which became the basis for almost every tank design after it. However the Panther was not terribly well armoured, and could not really fight the heavy tanks on an equal basis.
The first tank to 'get it all right' is generally considered to be the British Centurion tank, which (in its later versions) was able to take hits from the infamous German 88 mm gun, was armed with the deadly 105 mm Royal Ordnance L7 that was superior to anything in the field, and could reach 56 km/h due to its excellent 650-hp Rolls-Royce Meteor engine. The Centurion replaced all British medium cruiser tanks and led to the demise of the heavy infantry tank class entirely, becoming what the British referred to as the Universal Tank, soon to be known as the main battle tank in most forces, abbreviated MBT.
In response to the threat of antitank guided missiles (ATGMs), the focus in development shifted away from armor thickness, to armor technology. Gun technology remained remarkably similar even to WWI-era gun technology, with most tanks in service still being manually loaded, but with big advances in shell effectiveness.
Although the basic roles and traits of tanks were almost all developed by the end of WWI, the performance of twenty-first-century counterparts had increased by an order of magnitude. They had been refined dramatically in response to continually changing threats and requirements, especially the threat of other tanks. The advancing capabilities of tanks have been balanced by developments of other tanks and by continuous development of antitank weapons.
Design
The three traditional factors determining a tank's effectiveness are its firepower, mobility and protection. The psychological effect on enemy soldiers of a tank's imposing battlefield presence is called shock action.
Firepower is the ability of a tank to defeat a target. This takes into account the maximum distance at which targets can be engaged, the ability to engage moving targets, the speed with which multiple targets can be attacked, and the capability to defeat armoured vehicles or entrenched infantry.
Mobility includes the speed and agility of driving cross-country, the types of terrain that can be covered, the dimensions of obstacles, trenches, and water that can be crossed, the ability to cross small bridges, and the distance that can be covered before refuelling is required. "Strategic mobility" also includes the ability to travel at high speed on roads, and the ability to be carried on rail or truck transport. Traditionally AFV mobility is measured by the following metrics:
- engine power
- engine torque
- power-to-weight ratio
- road speed
- off-road speed (a somewhat nebulous figure given the possible variation)
- road range
- off-road range
- weight (bridge classification)
- ground pressure
- width of trench crossed
- vertical step climbed
- angle of slope that can be climbed
- angle of side slope that can be negotiated
- ground clearance
- unprepared fording depth
- prepared fording depth (if different)
Protection is the amount of armour, the type(s), how it is arranged (i.e., sloped or not), and which areas are given more protection (e.g., the turret and tracks) and which receive less (e.g., the rear of the chassis). It also includes low profile, low noise and thermal signature, active countermeasures and other methods of avoiding enemy fire, and the ability to continue fighting after damage has been sustained.
Tank design is traditionally held to be a compromise between these three factors—it is not considered possible to maximise all three. For example, increasing protection by adding armour will increase weight and therefore decrease manoeuvrability; increasing firepower by using a larger gun will decrease both manoeuvrability and protection (due to decreased armour at the front of the turret).
How the compromise is achieved is influenced by a combination of factors, including military strategies, budget, geography, political will, and the requirement to sell the tank to other countries.
Examples of how different countries are influenced in their decisions are as follows:
- Britain has historically opted for better firepower and increased protection at the expense of some manoeuvrability. Britain maintains a small, highly trained professional army, and so tank crew survivability is important. As limited resources may be available, the crew needs to be able to maintain their tanks in the field.
- The USA has a large army with sophisticated weaponry and a complex array of mobile support services. As their tanks are expected to rarely be away from support and repair units, less emphasis is placed on the crew's ability to maintain the tank themselves or to continue fighting with it once damage has been sustained.
- Germany's tanks were completely outmatched by the Soviet T-34 on the WWII Eastern front. It lost more of its insufficiently-developed Tiger and Panther tanks due to mechanical breakdowns than enemy action. As a result, German tanks since have been designed to be very manoeuvrable, with a resulting decrease in protection. Enhanced reliability and lower maintenance requirements have also been important design goals.
- Soviet tanks are traditionally rugged, simple for production and maintenance ("quantity turns into quality"), as exemplified by the T-34. State-controlled design development proceeds in incremental changes. Extensive maintenance is expected to be done in specialized depots.
- Israel is a small, but relatively rich, nation, with limited manpower in a hostile political environment. Its primary concern is therefore crew survivability. To this end it is the only nation to have produced a main battle tank with the engine placed at the front and fuel surrounding the crew, to increase protection.
- Further information: tank classification
Weapons
- Main article: tank gun
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 120mm calibre for Western tanks and 125mm 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. Some tanks can fire missiles through the gun. Smoothbore (rather than rifled) guns are the dominant type of gun today. The British Army and the Indian Army are now the only ones to field main battle tanks carrying rifled guns.
Modern tank guns are generally fitted with thermal jackets which reduce the effect of uneven temperature on the barrel. 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 then the right. This uneven cooling will cause the barrel to bend slightly and will effect long range accuracy.
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 small calibre (7.62 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 20mm cannon that has a high rate of fire and can 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 12.7-mm and 14.5-mm machine guns commonly carried on US 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, tank weapons were aimed through simple optical sights and laid onto target by hand, with windage estimated or assisted with a reticule. Range to the target was estimated with the aid of a reticule (markings in the gun sight which are aligned to frame an object of known size, i.e. a tank). Consequently, accuracy was limited at long range and concurrent movement and accurate shooting were largely impossible. Over time these sights were replaced with stereoscopic range-finders. These were eventually replaced by laser range-finders.
Most modern main battle tanks in the armies of industrialised countries use laser range-finders but optical and reticule 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, light-amplification, or thermal 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 reasonably accurately while moving.
Ammunition
There are several types of ammunition designed to defeat armour, including High explosive squash head (HESH, also called high explosive plastic, HEP), High explosive antitank (HEAT), and kinetic energy penetrators (KEP, or armour-piercing discarding sabot APDS). For accuracy, shells are spun by gun-barrel rifling, or fin-stabilized (APFSDS, HEAT-FS, etc.).
Some tanks, including the M551 Sheridan, T-72, T-64, T-80, T-90, T-84, and PT-91 can fire ATGMs (anti-tank guided missile) through their gun barrel or from externally mounted lauhchers. 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 the M551 and M60A2 out of their forces in favour of helicopters and aircraft for long range anti-tank roles, but CIS countries continue to employ gun-missile systems in their main battle tanks.