Some thicker armour was incorporated in tanks designed after the Second World War, bringing it up to a maximum of 200mm. However, such armour was confined to the front of tank turrets. When inclined at 60º or more from the vertical it had a horizontal shot line thickness of about 400mm, which implied an areal density of more than 3 tonnes per square metre of the area of the tank normal to the direction of attack. Significant increases in the thickness of armour were not practicable because of the consequent increases in the weight of tanks and hence a reduction in their mobility.
Moreover, increasing the thickness of homogeneous steel armour became less profitable as a result of the development of shaped charge weapons, against which it was less effective than against the armour-piercing projectiles of high-velocity guns.
This was brought out particularly clearly by the Panzerfaust anti-tank grenades with shaped charges that were used by the German infantry in the closing stages of the Second World War and that could penetrate up to 200mm of steel armour. The threat to tanks of shaped charge weapons was maintained after the war by rocket propelled anti-tank grenade launchers, like the US 3.5in. M20 `bazooka’, which could penetrate 280mm of armour. But it did not emerge in full until the appearance of anti-tank guided missiles, which began to be developed in Germany towards the end of the war. Their development was continued after the war in France and in the first instance resulted in the SS-10 guided missile, which had a warhead with a diameter of 165mm and could penetrate 400mm of armour. The SS-10 came into service with the French Army in 1953, but it was first used in action by the Israeli forces during the 1956 Sinai campaign.
The penetration capability of the SS-10’s successor, the SS-11 that was adopted by several countries, rose to 600mm, which was clearly more than any practicable thickness of steel armour. There was a need therefore to develop alternative ways of protecting tanks against shaped charge weapons. The search for the alternatives began in 1952 in the United States, where it was found that glass could be twice as effective in relation to its weight as steel armour in resisting the penetration of shaped charge jets. This led to the development of `siliceous armour’, which consisted of fused silica glass encased in steel that was successfully trialed as part of the US T95 tank programme. In 1958 it was subsequently proposed to incorporate it in the M60 tank, which was then being developed, but it was not adopted.
A somewhat similar solution to the problem was pursued in the Soviet Union when the T-64 tank began to be developed in 1962, which was provided with frontal hull armour consisting of two thick layers of a glass fibre composite sandwiched between steel plates. A similar type of composite armour with a high glass content was subsequently adopted in the T-72 and other Soviet tanks.
On the other hand, siliceous armour was no longer considered in the United States when the M1 tank began to be developed in 1972. Instead, what was initially considered in its design were arrays of spaced plates of steel and aluminium, which were expected to defeat shaped charge jets by eroding them in stages instead of defeating them by the properties of the armour materials.
As it happens, arrays of metallic plates were not adopted for the US M1 but were retrofitted to Soviet T-55 tanks. As it proceeded with the development of the M1 tank, the US Army became aware of and decided to adopt a new type of armour developed in Britain called Chobham armour. Chobham armour was developed at the Fighting Vehicles Research and Development Establishment of the British Ministry of Defence by G. N. Harvey and J. P. Downey from the basis of a research programme initiated in 1963, and was successfully incorporated for the first time in a Chieftain-based experimental tank designated FV 4211, which was built in 1971. It proved to be more than twice as effective against shaped charges as steel armour in relation to its weight, and when its existence became known it did much to restore the faith in tanks, which had been shaken by the grossly exaggerated claims about the vulnerability of tanks to anti-tank guided missiles that arose out of the 1973 Arab-Israeli War. The nature of Chobham armour has been kept secret by the British Ministry of Defence, although it has been succeeded by another type of armour called Dorchester, and in spite of it being obviously some form of spaced armour incorporating non-metallic materials as well as steel.
However, there is no secret about armour developed against shaped charges, which consists of an array of spaced sandwiches of steel plates with a rubber interlayer. When a sandwich is struck obliquely by a shaped charge jet the rubber expands, causing the plates to bulge and to move apart, interfering thereby with the jet, and if there are enough of the sandwiches arranged behind each other, ultimately breaking it up. Because of the way in which the sandwich plates deform, this type of armour is often referred to as `bulging armour’, and was described as early as 1973 in a patent applied for by M. Held. It has been incorporated subsequently in tanks such as the Soviet T-72M, which began to be produced around 1980 and which contained an array of 20 spaced steel and rubber sandwiches in each of two cavities in the front of its cast turret.
Some of the armours devised for protection against shaped charges incorporate layers of ceramics, such as aluminium oxide and silicon carbide. Ceramics first came into use as armour materials in the late 1960s in panels made to protect US helicopter pilots against bullets during the war in Vietnam. By the early 1970s ceramics were also recognized as being twice as effective in relation to their weight as steel against shaped charge jets. In consequence, they have been incorporated since then in a number of armour systems to erode the jets or the long-rod penetrators of APFSDS projectiles and to absorb their kinetic energy.
Ceramics have also been used to enhance the protection of light tanks and other light armoured vehicles against rifle and heavy machine gun bullets. In this case, their function has been to shatter the bullets by virtue of their greater hardness, and they have been used in the form of relatively thin tiles assembled into panels mounted on the outside of the basic metallic armour of the vehicles. Early examples of this were the Canadian M113 and the Swedish Pbv 302 armoured carriers that were deployed in support of the peace-keeping operations in Bosnia in the mid-1990s.
The ballistic protection of some light armoured vehicles has also been increased by the addition of a type of armour originally introduced in 1943 on German tanks and assault guns to increase the protection of their sides against Russian 14.5mm anti-tank rifles. It consisted of thin steel plates mounted some distance in front of the vehicles’ armour, which offered little resistance to the attacking bullets but tipped them so that as they struck the armour yawed and therefore hit less effectively. The use of this type of `tipping’ armour was revived in 1970 when it was adopted in the United States for a derivative of the M113 armoured carrier called the Armored Infantry Fighting Vehicle that was produced for the Dutch, Belgian and Egyptian armies and was also produced in Turkey, as well as South Korea.
The spaced-off tipping type of armour was developed further in Israel by the Rafael organization, who replaced the thin homogeneous steel plates by high hardness steel plates perforated by holes somewhat smaller than the diameter of the attacking bullets, which reduced their weight to one half of that of the equivalent solid plates and increased their ability to tip the attacking bullets. Called TOGA, the perforated plate armour was introduced on Israeli operated M113 carriers around 1985 and has been used since on other armoured vehicles, including some light tanks.
However, from the 1980s onwards the most common method of increasing the ballistic protection of light armoured vehicles has been to bolt on plates of high-hardness steel on to their steel or aluminium hulls, or of titanium on to aluminium hulls. An example of this has been the M2A2 version of the US Bradley Infantry Fighting Vehicle, which around 1986 had its original tipping armour consisting of two spaced 6mm steel plates replaced by a single 32mm thick appliqué armour plate.
A very different type of armour appeared on Israeli M60 and Centurion tanks during the 1982 Israeli invasion of the Lebanon. This was explosive reactive armour, or ERA, which was devised by M. Held from the basis of the studies he carried out in 1969 in Israel on behalf of the Messerschmitt- Bolkow-Blohm missile company on the effects of shaped charge hits on the tanks disabled two years earlier during the Six Day Arab-Israeli War. Held patented his ideas in 1970 and they were subsequently put into effect in Israel by the Rafael organization in the form of the Blazer explosive reactive armour.
In essence, ERA consists of sandwiches of two steel plates with an explosive interlayer, which is set off when a sandwich is penetrated by a shaped charge jet and which, when the plates are at an angle to the jet, drives the plates apart into its path, disturbing or disrupting it. Originally the plates were only 2 or 3mm thick, but when the sandwiches incorporating them were at an angle to the jet, as they had to be, they could still reduce its penetration of armour by as much as 70 per cent.
The appearance of ERA on Israeli tanks was followed by its large scale installation on Soviet tanks, starting in 1983 with T-64BV. Having decided to use ERA, the Soviet Army took the lead in developing a heavy version of it with sandwich plates of 15mm or greater thickness, which were effective not only against shaped charge jets but also against the long-rod penetrators of APFSDS projectiles. The Soviet Army also took the lead in the development of tandem ERA consisting of pairs of sandwiches separated by an air gap, which was considerably more effective than the original type of ERA against single shaped charges. Tandem ERA could also defeat warheads with tandem shaped charges that incorporated a precursor charge designed to clear any single ERA sandwich out of the way of the main charge. An example of such tandem ERA described in a Russian journal incorporated an outer light ERA sandwich followed by a layer of a damping material and a sandwich of heavy ERA. This, together with a tank’s steel armour, was claimed to be capable of defeating the tandem warhead of the US AGM-114F Hellfire guided missile, which has a diameter of 178mm and is thought to be capable of penetrating up to about 1,500mm of armour.
What emerged out of all the development of armour was a trend towards the use of multi-layered protection systems combining several different types of armour. Thus the outer layer of armour might consist of very steeply sloped thin high-hardness steel, which would fracture penetrators striking it or at least throw them to some degree off their trajectory. Examples of this are the sharply pointed noses of the turrets of several tanks modified during the 1990s, including the German Leopard 2A5 and the Chinese Type 99. The nose armour might be followed by tandem ERA to break up long-rod penetrators or disrupt shaped charge jets, and then by the tank’s main armour, which could incorporate ceramics and which would absorb the kinetic energy of penetrator fragments or of jet particles. The effectiveness of some tanks’ frontal armour that has been developed has been estimated to be equivalent to as much as 900mm of steel armour against kinetic energy projectiles and to well over 1,000mm of armour against shaped charges.
After its successful introduction on tanks, the use of ERA was extended to lighter armoured vehicles. This initially created problems because lighter vehicles did not, unlike tanks, have armour thick enough to absorb the front part of a shaped charge jet, which inevitably passes through an ERA sandwich before it is set off, and because the flying rear plate of a sandwich could damage thin armour. To overcome these problems, Rafael developed a hybrid ERA by backing an explosive sandwich with an elastomer and another steel plate. This reduced the impact of the ERA on the host vehicle and provided additional resistance to bullets.
The use of ERA on armoured vehicles other than tanks was already being considered in the 1980s but it was not generally implemented until the following decade, partly because there was no urgent requirement for it and partly because of concern about the collateral damage that it could cause. Thus when the second generation of the US M2 Bradley infantry fighting vehicle was being developed in the 1980s, only a part of the fleet was fitted for, but not with, ERA. However, after the US forces invaded Iraq in 2003 hybrid ERA became standard on the Bradleys and it was also fitted to some of the Israeli M113 carriers. Subsequently the British Ministry of Defence was persuaded to have it fitted also to the Bulldog, the modernized version of the FV 432 armoured carrier, and the Warrior infantry fighting vehicle.
Hybrid ERA provided a badly needed response to the extensive use in Iraq of RPG-7 rocket propelled anti-tank grenades by the fedayeen or militants. The situation that had arisen in Iraq in 2003 also revived the use by the US Army of another form of protection against RPG-7 grenades, which was simpler and cheaper than ERA but which was only partially effective against them. It consisted of horizontal steel slats set apart at less than the diameter of the RPG-7 grenades so that one side or the other of a grenade’s nose would hit a slat as it flew between the slats and would be crushed, thereby short-circuiting its fuse and preventing detonation of the grenade. However, some grenades are bound to hit the edges of the slats with their nose impact fuse and thus to detonate. The probability of this happening is such that slat armour is only effective at most against about 60 per cent of the hits.
A form of slat or the very similar bar armour was first used in the 1960s by the US Navy on the gun boats that it operated in the Mekong delta during the Vietnam War. It was also used by the Soviet Army in Afghanistan in the 1980s and in Chechnya in 1995 on T-62 tanks, and it was also fitted to the turrets of some Chinese-built Type 69 tanks used by the Iraqi Army in 1991 during the First Gulf War. The US Army developed bar armour for its M113 carriers as early as 1966 but did not start using it until 2003, immediately after the invasion of Iraq, when it came up against the widespread use of RPG-7 by the Iraqi fedayeen. Slat armour then began to be used widely not only by the US Army but also by others, including the British Army. Nevertheless, in 2005 the British Ministry of Defence still considered slat armour as something new and regarded a contemporary article about it as revealing secrets.
Slat armour originally fitted by the US Army to its Stryker eight-wheeled armoured carriers weighed 2,231kg, or about as much as a suite of hybrid ERA, which constituted an undesirable increase in their weight. It was consequently followed by the development of several lighter alternatives, including L-Rod armour developed by BAE Systems in which steel slats were replaced by bars of high strength aluminium and which had half the weight of the original type. An even lighter version was developed in Switzerland by RUAG using a diamond-patterned mesh of very high strength steel wire, and still lower weights have been achieved with fibre net systems, such as RPGNets developed in the United States or Tarian developed in Britain, which squash the noses of the grenades that become enmeshed in them.
The quest for ballistic protection that would be more effective in relation to its weight than steel led several years earlier to the use of aluminium armour. This began to be developed in the United States around 1956 and three years later the US Army ordered the production of the M113 armoured carrier, which became the first aluminium armoured vehicle to be produced in quantity and subsequently the most numerous tracked armoured vehicle to be built outside the Soviet Union. Britain, France, Italy and South Korea followed the example of the United States and produced aluminium armoured infantry fighting vehicles, like the US M2 Bradley, of up to 20 and eventually 30 tonnes. On the other hand, Germany, Sweden and Singapore built similar vehicles of steel armour. In spite of the lower density of aluminium armour, there has been little to choose between vehicles with the two kinds of armour so far as their weight is concerned, but those of aluminium armour have been somewhat easier to manufacture and are structurally stiffer because their walls have to be thicker for a similar level of ballistic protection.
The structural stiffness of aluminium armour hulls makes them particularly attractive where most of the ballistic protection comes from other materials, such as high-hardness steel or ceramic tiles, which are structurally parasitic. This was also the case with the Chobham armour of FV 4211, which was designed with a hull of aluminium armour, relying on the Chobham armour packs for most of the ballistic performance. But the combination of Chobham armour with aluminium armour was not considered entirely satisfactory and it was adopted for the hull of only one other tank, the 43-tonne Vickers Valiant designed for export by Vickers Defence Systems in 1977 but not developed beyond the prototype stage. Some light tanks, such as the US M551 Sheridan and the British Alvis Scorpion, have also had hulls of aluminium armour, but the levels of protection they were expected to provide were very much lower than that of FV 4211 and Vickers Valiant.
Interest in the possible alternatives to steel extended at one time beyond aluminium armour even to composite materials made of resin bonded glass fibres. The latter began to be considered by the US Army Materials Technology Laboratory in 1976 and attracted the interest of the US Marine Corps, which in 1983 ordered two M113-type armoured carriers to be made with composite hulls. When one of them was tested, it was adjudged to be superior to the standard aluminium hulled carriers, which encouraged the US Army to order a composite armour analogue of the larger 22-tonne aluminium armoured Bradley infantry fighting vehicle. This was completed by FMC Corporation in 1989, when the writer was able to examine its construction.
The hull of what became known as the Composite Infantry Fighting Vehicle or CIFV was made of high strength aerospace quality S-2 glass fibres bonded by a thermosetting polyester resin. The laminate that made up its walls contained as much as 68 per cent of glass by weight and was superior ballistically to the aluminium armour of the M113 carriers. CIFV was fitted with the standard turret as well as the engine, transmission and suspension of the Bradley and successfully completed a 6,000 mile automotive test programme, which encouraged further work in the United States on composite hulled armoured vehicles.
One sequel to it was the construction in 1993 of a Heavy Composite Hull, or HCH, which resembled that of the US M1 tank. It was intended to be part of a 45-tonne composite hulled, US tank, but the latter was never built. However, another and more realistic project launched by the US Army in 1993 led to the construction of the Composite Armored Vehicle Advanced Technology Demonstrator or CAV-ATD, a 20-tonne vehicle that might have served as a model for an armoured reconnaissance vehicle but that had no direct follow-up after it was rolled out in 1997.
The incentive to develop composite vehicles was the hope that they would be significantly lighter than conventional vehicles with metallic hulls, and savings in weight of up to 33 per cent were claimed. But, even if this were true, it only applied to hulls, which in general account for only one third of the total weight of an armoured vehicle. In consequence, the overall saving in weight would be only of the order of 10 per cent, and this would hardly justify the adoption of composite armoured vehicles, bearing in mind the problems associated with their production and their considerably higher cost.
Nevertheless, interest in composite armoured vehicles extended beyond the United States. In fact, a study of a composite hull for the Scorpion light tank was carried out in Britain for the Fighting Vehicles Research and Development Establishment as early as the 1960s. Nothing came of it, but in 1993 the Defence Research Agency, which succeeded FVRDE, embarked on the development of a composite hulled vehicle of about 22 tonnes to demonstrate the possibility of basing a future reconnaissance vehicle on it. It was called the Advanced Composite Armoured Vehicle Platform or ACAVP, and was completed in 2000, after which it successfully passed extensive automotive trials but, like the US CAV-ATD, it had no successor.
The only composite armoured vehicle to go into production and service has been the CAV 100, which consists of a resin bonded glass fibre body mounted on the chassis of the 3.5-tonne 4×4 Land Rover light truck. More than one thousand CAV 100s were built by Courtaulds Aerospace from 1992 onwards, mainly for use by the British Army in Northern Ireland where it acquired the name `Snatch’ because of its use in grabbing rioters. Its composite body provided some protection against small arms, but it proved entirely inadequate, with fatal consequences, when the British Army mistakenly deployed it in the mid-2000s in Iraq and then in Afghanistan, where it was exposed to improvised mines and anti-tank grenades.
The only other large scale and far more effective use of glass fibre composites has been as the intermediate component of the glacis armour of Soviet tanks from the T-64 onwards, which has been mentioned previously. Because of their high glass content, glass fibre composites made a very effective contribution in this case to the frontal protection of tanks against shaped charge weapons.
An entirely different form of protection, particularly against weapons with shaped charge warheads, came to be represented by active protection systems. There are several different types of them, but they all consist of three basic components. One of them is a threat detection system, usually based on millimetre wave radar. Another component is a `kill’ system consisting of counter-missiles with blast or fragmentation warheads or of focused blast modules. The third component is a computer-based control system that processes information about the threat and activates the countermeasures.
An active protection system called a Dash-Dot Device, which incorporated radar for threat detection and linear shaped charges as countermeasures, was proposed as early as 1955 in the United States at the Picatinny Arsenal. However, actual development of active protection systems did not become evident until the 1980s. In fact, in 1983 after six years of development the Soviet Army completed the installation of the Drozd active protection system on a T-55AD tank. This pioneer Soviet system consisted of a radar module and a cluster of four launchers of 107mm rockets with fragmentation warheads on each side of a tank’s turret, which formed the countermeasures. Between them they covered a frontal arc of 80º, which would have been sufficient for protection during frontal attacks in open terrain. As it is, some tanks fitted with the Drozd system were employed towards the end of the 1979-89 Soviet occupation of Afghanistan, where according to the system’s developers they defeated 80 per cent of anti-tank grenade attacks.
Elsewhere, during the 1970s and 1980s, attention was focused on simpler `soft kill’ protection systems, which were not designed to damage or destroy threat missiles but merely to make them miss their targets. The basic component of such systems were infrared jammers, which interfered with the guidance of anti-tank missiles with semi-automatic command-to-line-of-sight or SACLOS guidance that were perceived at the time to be a major threat to tanks. A `soft kill’ defence system based on infrared jammers was deployed on French AMX 30 B2 tanks during the 1991 Gulf War, and at about the same time another such system called Shtora appeared on Russian tanks. The latter also incorporated a laser warning receiver that could trigger smoke grenade launchers to produce smoke screens that would blind laser designated missiles with semi-active guidance.
Further development of the `soft kill’ systems exemplified by the MUSS system produced in Germany involved the addition of a missile warning receiver capable of detecting the ultra-violet emissions of missiles’ rocket plumes and consequently of alerting the infrared jammers, which would otherwise have to be switched on continuously when missile attacks were expected and thereby could reveal the tank’s position.
Although `soft kill’ active protection systems can prevent some anti-tank missiles from hitting their targets, they are ineffective against others, and in particular against unguided anti-tank rockets, which became the principal threat to tanks by the time Russian forces moved into Chechnya in 1995 and US forces moved into Iraq in 2003, when the scene of operations shifted to urban environments. In consequence the focus of attention began to turn from soft to hard kill active protection systems, which were potentially capable of defeating a much wider range of threats.
An early object of the renewed interest in hard kill active protection systems was the Russian Arena system, which appeared in 1993. In addition to radar, Arena was based on the use of fragmentation cassettes launched from a collar- like mounting around the turret of a tank as its kill mechanism so that, unlike Drozd, it provided almost all-round protection and it produced far less risk of collateral damage. However, although it aroused a great deal of interest when it appeared on a T-80 tank, it did not advance beyond experimental installations.
It was only 27 years after the appearance of the Russian Drozd that another hard kill active protection system came into use. This was Trophy, which began to be developed in Israel by Rafael around 1995 and which fired at the threat missiles a beam of small explosively formed penetrators from one of two automatically reloadable launchers mounted at the sides of a tank’s turret. The development of Trophy was accelerated by the 2006 war in the Lebanon, where Israeli forces came up against the powerful Russian-made Kornet (9M133) anti-tank guided missiles acquired by Hezbollah through Syria. In consequence, 100 Trophy systems were ordered in 2007 for installation on Merkava Mark 4s, and a battalion of them was subsequently deployed along the frontier with Gaza, where in March 2011 for the first time Trophy automatically destroyed an anti-tank rocket fired at a Merkava by Palestinian militants.
Several other hard kill systems have been developed since the 1990s, including AWISS developed in Germany by EADS, Iron Fist developed by the Israel military industries and LEDS 150 developed in South Africa by Saab Avitronics. Although they differ from each other in several respects, all these systems have been designed to defeat attacking missiles at some distance from the defended vehicle by launching counter-missiles with fragmentation or blast warheads at them from rapidly traversable two to six tube launchers, which ensured all-round protection.
Hard kill active protection systems have also been developed that do not launch counter-missiles but fire directly at the attacking missiles from the defended vehicles. The Israeli Trophy belongs to this category of active protection systems, but most of them incorporate counter-measures that are distributed around a vehicle and defeat threats close to it by blast. This minimizes the risk of collateral damage, but because of the very short distance at which the threat is attacked requires the system to have a very short reaction time. The principal example of this kind of system is AMAP developed in Germany by IBD Deisenroth Engineering; others include the Iron Curtain developed in the United States by Artis and Zaslon developed in the Ukraine.
In addition to the threat posed by various missiles as well as other anti-tank weapons, tanks have also had to be protected against anti-tank mines. The latter emerged as a threat almost as soon as tanks came into use during the First World War, when in 1918 the German Army began to use mines improvised from artillery shells. However, there was little interest in anti-tank mines for some time after the First World War and there was no significant use of them again until the Spanish Civil War of the 1930s. They were also employed by the Finnish Army during the 1939-40 war between Finland and the Soviet Union, but it was only in 1942 that they began to be used extensively by the German Army in North Africa and by the German and Soviet armies in Russia.
The use of mines resulted in as much as 18 per cent of the Allied tank casualties in North Africa and 23 per cent of the casualties in Western Europe in 1944-45. However, much of the damage was confined to the running gear of tanks and was repairable, particularly when tanks had externally mounted suspension units. Moreover, mines were laid to create minefields to restrict the freedom of manoeuvre of armoured formations rather than to destroy tanks. In consequence, considerable effort was devoted during the latter part of the Second World War and for some time afterwards to the development of devices such as flail tanks for the clearing of paths through minefields instead of improving the mine resistance of individual tanks.
The situation changed in the second half of the 20th century when mines became the principal weapons of the insurgents, terrorists and others involved in the various asymmetric wars of that period. The change was brought out by the war in Vietnam, in which as many as 69 per cent of the US armoured vehicle casualties were caused by mines. However, in contrast to the Second World War where the armoured vehicles concerned were mainly tanks, in Vietnam most of the vehicles were lighter and less robust. Moreover, the Vietnamese forces were short of anti-tank weapons other than mines.
The war in Vietnam had little impact on the design of tanks, although it led to the installation of additional steel belly plates in some of the lighter vehicles, such as the US M551 Sheridan light tank. The 1979-89 war in Afghanistan in which a number of Soviet tanks were destroyed by mines laid by the mujahedin produced greater repercussions, at least so far as Soviet tanks were concerned. In particular, it led to a number of modifications to them that were later widely adopted elsewhere. Thus to reduce the risk of the driver’s seat being hit by a belly plate bulging under the impact of a mine explosion, T-62 tanks were fitted with an additional outer spaced-off belly plate under the front part of the hull, although this seriously reduced the ground clearance. Then in T-72 and other tanks the risk of the bulging belly plate hitting the driver’s seat was reduced without affecting the ground clearance by suspending the seat from the roof of the hull instead of keeping it fixed as usual to the floor, which disconnected them and lifted the seat well off the floor and the belly plate.
Like the war in Afghanistan, the 1964-79 war in Rhodesia (now Zimbabwe) also involved extensive use of mines but not of tanks. However, it led to the development of a new category of mine resistant wheeled armoured vehicles that were developed further with great success in South Africa. They included the 4×4 Buffel, 3,500 of which were built and which reduced dramatically the number of casualties caused by terrorist mines, and its successor, the Casspir. Like the Buffel, the 4×4 Casspir had a hull with a blast deflecting V-bottom and, in spite of its relatively light weight of 11 tonnes, was claimed to be able to survive the explosion of three stacked anti-tank mines, or 21kg, of TNT under one of its wheels or of 14kg of TNT under its hull. Since it was first built in 1981, about 2,500 Casspirs have been produced and they were used as armoured personnel carriers in counter-insurgency operations in South West Africa (now Namibia) and elsewhere, with casualties occurring in them due to mine explosions only when they encountered a penetrator mine.
A few South African Mamba mine resistant vehicles derived from the Casspir were procured by the British Army in 1995 for the contemporary peace-keeping operations in Bosnia that came up against widespread use of mines, including Yugoslav TMRP-6 penetrator mines. At about the same time the Krauss-Maffei company began to develop in Germany the 4×4 Dingo mine resistant vehicle, which was to be produced later in quantity. However, mines were still not a major concern to US and other NATO forces, and the design of their tanks that dated from the Cold War was focused on protection against horizontal attack by tank guns and anti-tank weapons and not against mines. US and British forces were therefore unprepared for the extensive use of improvised mines by the Iraqi insurgents that followed the invasion and occupation of Iraq in 2003.
Prior to these events, the usual threat to tanks was considered to consist of industrially produced blast mines with contact fuses that exploded when a tank’s track ran over them, or less frequently with tilt rod or magnetic influence fuses that would set off mines not only under tracks but also, and more dangerously, under the bellies of tanks. Worldwide studies carried out in the United States and Germany established that the most common of the industrially produced anti-tank mines contained 7 to 8kg of explosive and the highest level of mine threat specified by NATO was the explosion, of 10kg of TNT under the hull of a vehicle.
However, many of the blast mines improvised by the Iraqi insurgents weighed more that this. In fact, one of them that wrecked a US M1A2 tank in October 2003 is believed to have contained more than 100kg of explosive. A year earlier, an Israeli Merkava Mark 3 was similarly wrecked on the border of Gaza by a mine containing almost 100kg of explosive detonated by remote control by Palestinian militants. Evidently even well-armoured tanks cannot withstand such large mines, but their resistance can be improved, as has been shown by Merkava Mark 4, which has been provided, among others, with a thick additional belly plate of special steel and one of which even survived the explosion of a 150kg mine laid by the Hezbollah during the 2006 war in the Lebanon with the loss of only one crew member. What is more, very heavy mines are not easy to plant and although many mines laid by the insurgents have weighed more than 10 kg they have not, in general, weighed much more than about 20kg, which is about as much as an insurgent could carry any distance.
In addition to improvised blast mines, tanks and other armoured vehicles need to have their protection improved against the use of improvised penetrator mines, which was foreshadowed by the appearance of such mines in Southern Africa and Bosnia. Penetrator mines consist of explosive charges with shallow copper-lined cavities that resemble shaped charges but instead of copper jets shoot copper slugs with velocities of up to 2,000m/s, which may be compared to kinetic energy projectiles. Their armour-piercing capability is less than that of the shaped charges of the same size, but it does not fall off as rapidly with distance as that of the latter, which makes them particularly effective as remotely controlled off route mines, and in this role they were used extensively by the Iraqi insurgents.