Encyclopedia
A
tank is a
tracked armoured fighting vehicle, designed to engage enemy forces by the use of direct fire. A tank is characterized by heavy
weapons and
armour, as well as by a high degree of mobility that allows it to cross rough terrain at relatively high speeds. While tanks are expensive to operate and logistically demanding, they are among the most formidable and versatile weapons of the modern battlefield, both for their ability to engage other ground targets and their shock value against
infantry.
While tanks are powerful fighting machines, they seldom operate alone, being organised into armoured units in combined arms forces. Without such support, tanks, despite their armour and mobility, are vulnerable to infantry,
mines,
artillery, and air power. Tanks are also at a disadvantage in
wooded terrain and urban environments, which cancel the advantages of the tank's long-range firepower, limit the crew's ability to detect potential threats, and can even limit the turret's ability to traverse.
Tanks were first used in the
First World War to break the
deadlock of the trenches, and they evolved gradually to assume 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 armour tactics have undergone many generations of evolution over nearly a century. Although weapons systems and armour continue to be developed, many nations have reconsidered the need for such heavy weaponry in a period characterised by unconventional warfare.
History
- Main article: History of the tank
World War One: The first tanks
The fighting conditions on the
Western Front prompted the
British Army to begin research into a self-propelled vehicle which could cross trenches, crush
barbed wire, and would be impervious to fire from
machine-guns. Having already seen a
Rolls-Royce Armoured Car used by
Royal Naval Air Service in 1914, and aware of schemes prompted by Major Ernest Swinton 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 Landships Committee created the first successful prototype tank, nicknamed
Little Willie, which was tested by 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. Tanks were later used again to great effect in the
Battle of Amiens, Allied forces breaking an entrenched German position with armoured support. 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 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 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
armoured fighting vehicles .
Germany fielded a small number of tanks, mainly captured, during World War I. They only produced approximately twenty of their own design, the
A7V. 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.
Demands from infantry to have tanks close by during attacks would have pernicious effects on British tank design and tactics well into WW2.
The interwar years: advances in design and tactics
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 armoured force during the 1920s. 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 Armoured 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 Armoured 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 United Kingdom. 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 tanks, or cruiser tanks as they were known in the United Kingdom, were somewhat heavier and focused 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 enemy anti-tank 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 anti-tank guns and similar weapons, including dedicated anti-tank 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 effective anti-tank 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.
The tank in World War II
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 the armour, weaponry and cross-country performance while being equal in speed. 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 , 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 . 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 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
After WWII, tank development proceeded largely as it had before, with improvement 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 anti-tank 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 inspiration 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.
A highly successful post-war tank was the Soviet
T-54, which started production in 1947. This successor to the
T-34 of World War II represented a direct evolution of that tank's design principles, improving on its low profile, good armour, high mobility, and adding a 100mm tank gun.
Another new tank was the British
Centurion tank. Centurion marks built in the late 1950s were able to resist hits from the infamous German
88 mm gun, were armed with the deadly 105 mm Royal Ordnance L7, and could reach 56 km/h due to the excellent 650-hp Rolls-Royce Meteor engine. The Centurion replaced all British medium cruiser tanks and finally 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 , the focus in development shifted away from armour thickness, to armour 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 anti-tank 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
- road range
- off-road range
- weight
- 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
Protection is the amount of armour, the type, how it is arranged , and which areas are given more protection and which receive less . 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 .
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 speed and 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 has benefited from a technically superior armament industry and, following initial encounters with the T-34, have often mounted the most advanced main guns. Importance being placed on vehicle range, speed, and fire control systems due to the highly aggressive posture of German armoured doctrine.
- Soviet tanks are traditionally rugged, simple for production and maintenance, as exemplified by the T-34. State-controlled design development proceeds in incremental changes. Extensive maintenance is expected to be done in specialised depots. Russian tanks utilise an auto-loader to reduce both crew size and delay between shots.
- 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, the Merkava.
- French tanks tend to favour manoeuvrability and firepower over heavy armour. For instance, the Leclerc is relatively light , but is capable of accelerating from 0 to 32 km/h in 5 seconds, and braking at 7 m/s˛. French tanks also use an auto-loader.
- Pakistan is a relative newcomer to the tank development game. Facing a very varied opertational situation, the army has traditionally been forced to use different types of tanks in differnt sectors, for example, heavy American style tanks are were used in the Punjab plains, with its well developed network of bridges and roads, while lighter more mobile Chinese Tanks were used in the pooerer southern desert sectors of Sindh. To reduce the logistical problems, the army developed the MBT-2000, Al Khalid Tank, a tank with sufficent armour protection and firepower for the north, but able to fight in the south as well.
Weapons
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 tanks.
Tank guns have been able to fire many types of rounds, but their current use is commonly limited to kinetic energy
penetrators and
high explosive rounds. Some tanks can fire missiles through the gun. Smoothbore 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 than the right. This uneven cooling will cause the barrel to bend slightly and will affect 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
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
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, tank weapons were aimed through simple optical sights and laid onto target by hand, with windage estimated or assisted with a reticle. Range to the target was estimated with the aid of a reticle . 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.
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 , 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 ,
High explosive anti-tank , and
kinetic energy penetrators . For accuracy, shells are spun by gun-barrel
rifling, or fin-stabilised .
Some tanks, including the
M551 Sheridan,
T-72,
T-64,
T-80,
T-90,
T-84, and
PT-91 can fire
ATGMs 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 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.
Protection
The main battle tank is the most heavily armoured vehicle in modern armies. 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
antitank guided missiles; antitank
mines, larger
bombs, and direct
artillery hits, which can disable or destroy them. Tanks are especially vulnerable to airborne threats. Most modern MBTs do offer near complete protection from artillery fragmentation and lighter antitank weapons such as
rocket propelled grenades. 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.
Armour
Most armoured fighting vehicles are manufactured of hardened steel plate, or in some cases aluminium. The relative effectiveness of armour is expressed by comparison to rolled homogeneous armour.
Most armoured vehicles are best-protected at the front, and their crews always try to keep them pointed toward the likeliest direction of the enemy. The thickest and best-sloped armour is on the glacis plate and the turret front. The sides have less armour and the rear, belly and roof are least protected. Today, tanks are vulnerable to specialised top-attack missile weapons and air attack. During WW2, aircraft
rockets earned a formidable reputation, especially in France after the
Normandy landings ; post-war analysis revealed many reported kills were near-misses. Aircraft cannon firing armour-piercing ammunition, such as the
Hurribomber's 40mm or
Stuka's 37mm, could be effective, also. Even a simple
Molotov cocktail on the engine deck, however, may disable most tanks.
Before the Second World War, several tank designers tried
sloping the armour on experimental tanks. The most famous and successful example of this approach at the time was the
T-34. Angling armour plates greatly increases their effectiveness against projectiles, by increasing the effective perpendicular thickness of the armour, and by increasing the chance of deflection. German tank crews were said to be horrified to find that shots fired at the angled plates of T-34s would sometimes simply ricochet.
Even light infantry antitank weapons can immobilise a tank by damaging its suspension or track. Many tracked military vehicles have side skirts, protecting the suspension.
High explosive anti-tank weapons , such as the
bazooka, were a new threat in the Second World War. These weapons carry a warhead with 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, were found to cause HEAT rounds to detonate too far from the main armour, greatly reducing their penetrating power.
Some anti-tank ammunition 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. As a defence, some vehicles have a layer of anti-spall material lining their insides.
Since the 1970s, some tanks 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 is comprised of spaced
ceramic blocks contained by a
resin-
fabric matrix between layers of conventional armour. A form of Chobham armour is encased in
depleted uranium on the very well-protected
M1A1 Abrams MBT.
The Israeli
Merkava tank takes the design of protection systems to an extreme, using the engine and fuel tanks as secondary armour.
When the armour is defeated then 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.
Grenade launchers, smoke and passive defences
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. The
smoke screen 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 of light.
Some smoke grenades are designed to make a very dense cloud capable of blocking the laser beams of enemy target designators or range finders and of course obscuring vision, reducing probability of a hit from visually aimed weapons, especially low speed 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-built
Leclerc, the 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. 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 .
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 than reactive armour. An APS uses radar or other sensing technology to automatically react to incoming projectiles. When the system detects hostile fire, it calculates a firing resolution and directs an explosive-launched counter-projectile to intercept or disrupt the incoming fire a few metres from the target.
Exposed crew
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, with no personal protection save his
helmet and a flak jacket. In this rather high position 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. Tank
periscopes and other viewing devices give a sharply inferior field of vision and sense of the countryside, despite constant advances in optics and electronics. 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.
Mobility
There are essentially three main aspects of mobility to consider, the tank's basic mobility such as its speed across terrain, the ability to climb obstacles and its overall battlefield mobility such as range, what bridges it can cross, and what transport vehicles can move it and turning. Mobility is what tankers and tank designers call 'agility'. 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. The second is the ability of the tank to be readily transported within a theatre of operation. 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 main battle tank is designed to be very mobile and able to tackle most types of
terrain. Its wide
tracks disperse the heavy weight of the vehicle over a large area, resulting in a specific ground pressure that might be lower than that of a man's foot . 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 30 to 50 km/h. The
road speed may be up to 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. But 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 for a day, given the variety and unpredictability of off-road terrain .
Since an immobilised tank is an easy target for mortars,
artillery, and the specialised
tank hunting units of the enemy forces, speed is normally kept to a minimum, and 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 that of 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 that the
