Chobham armor, reactive armor, cage armor, and boilers? If you’ve been keeping up with modern conflicts you might have heard of at least three of these terms before. Although the first three do have armor in their name and are used to protect armored vehicles like tanks, they seemingly have nothing in common. Tank armor, in general, seems to be a confusing topic at first, so let's dive in and explain how this revolutionary piece of technology was developed, and what this all has to do with boilers. The Birth of the Tank Modern tank armor has evolved significantly since these weapons of war were first introduced to the battlefield in World War I. The lumbering vehicles were given the codename “Tank” by the British army as a cover to confuse the Germans, and since they were being made in factories that made boilers, the name acted as a perfect cover for the revolutionary project. This is why we mentioned boilers in the intro! The first tanks were made in quite the same fashion: riveted sheets of steel, sometimes bolted together. Vertical, thin, rolled sheets of steel were used instead of hardened steel to save on weight and cost, so these early prototypes rarely stopped anything more than rifle shots or light machine gun bullets. Since then, advancements in armor sloping, metal technology, and exotic materials have been instrumental in making armored vehicles more resilient on the battlefield. But many of these more modern advancements only came about later on as the Cold War pitted the U.S. against the Soviets. Before these leaps in technology, a foundation had to be set, this is where World War II armor developments come in. Early Tank Armor Developments Through World War II The birth of tank warfare in World War I was marked by the introduction of primitive armored vehicles. The first tanks were relatively slow and lightly armored, and they primarily relied on mobility and firepower to overcome enemy defenses. These early tank designs used rolled steel armor, often only around 6-12 millimeters thick. This armor was capable of protecting against small arms fire and artillery shell splinters, but was vulnerable to direct hits from artillery and light anti-tank weapons. World War II marked a significant turning point in the evolution of tank armor. The conflict saw the development of more sophisticated tanks, with thicker armor, the replacement of riveted plates with cast steel hulls and turrets, and better-sloped armor that provided better effective protection than non-sloped armor and had a chance to deflect some lower powered shells. German tanks like the PzKpfw. VI Tiger I and the more massive Tiger Ausf. B, known as the King Tiger or Tiger II, featured thick armor, while the PzKpfw. V Panther and Soviet T-34, IS-I and IS-II featured well-sloped armor that was difficult for most anti-tank weapons to penetrate, at least from the front. While the United Kingdom and the United States were slower to adopt sloped armor designs, they compensated by using thicker armor in some of their main battle tanks. The British Matilda II tank, for example, used thick frontal and side armor to great effect early in the war, and proved difficult for German gunners to knock out. The thickness of the armor, however, came at a price: the tank was heavier and slower than many other tanks of the time, and the British were never able to upsize its turret to replace the already obsolete 2-pounder main gun. The majority of Western tanks, specifically the US-built M-3 Grant and M-4 Shermans, suffered from weaker armor and a lack of high-powered anti-tank guns that could penetrate their German opponents. While the Germans had the Borsig KwK Pak 42 75mm high-velocity cannon, capable of penetrating American or British armor at very long range, even more effective was the legendary 88mm KwK Pak 36 gun, derived from the 88mm Flak 36 anti-aircraft gun. Against this cannon, no Allied armor was safe. The Cold War: Arms Race and Composite Armor The Cold War era marked a substantial shift in tank design and armor technology. The United States and the Soviet Union, along with other European nations, engaged in an arms race to produce the most advanced tanks. This period saw the development of revolutionary tank and armored vehicle designs, as well as the emergence of composite armor, a revolutionary development in tank protection. Let’s look at the two sides of the Cold War arms race and how their military doctrines influenced their developments. Soviet Tank Armor Soviet tanks, particularly the T-54 and T-55, were equipped with composite armor that utilized various layers of steel and non-metallic materials. This made the armor resistant to both kinetic penetrators and chemical energy munitions. Soviet tanks were also designed with sloped armor for improved protection against a wide range of threats. However, the priority of Soviet tank designers appeared to be in keeping their tanks as low as possible. On average, their tanks were anywhere from one to two feet lower than their Western counterparts. While that did make for a harder-to-hit target, it also limited how far their main gun turret could depress, which in turn limited the tank’s capability to go “hull down,” which is when a tank hides behind a low hill or berm and exposes only its turret and main gun to enemy fire. This makes sense considering the Soviets were preparing their military to fight a conflict against the west across The Great European Plain, a flat part of North-Eastern Europe stretching from Northern Germany to modern day Ukraine. British and US Tank Armor The United Kingdom contributed to the development of composite armor through the invention and development of Chobham armor. Chobham armor is a composite material that combines a classified blend of ceramic sheets, sections of steel, and other materials to provide enhanced protection. This innovation made British tanks like the Challenger 2 highly resilient to enemy direct-fire weapons on the battlefield. The exact composition of Chobham armor is still a somewhat closely guarded secret, though analysts suggest it’s made of alternating layers of nylon micromesh, titanium, and ceramic material bonded together. In response to the Soviet threat, the US developed composite armor solutions such as their Chobham-derivative armor used on the M1 Abrams tank. The Abrams featured a composite armor package that included depleted uranium layers, which offered exceptional protection against kinetic energy penetrators, as well as angled sheets internal to the armor that helped direct away and deflect any incoming blast from an anti-tank round. Details about this armor are also technically still meant to be top-secret, though leaks on the Internet supposedly show just how the sandwiched layers are utilized in vital areas around the tank, such as the turret’s gun mantlet, the front glacis plate, and other vital areas. This early version was designated “non-explosive reactive armor,” or NERA. Reactive Armor and Its Introduction During the late Cold War and post-Cold War era, reactive armor became an important addition to tank protection. Reactive armor is a type of modular armor that explodes outward when hit by a projectile, disrupting the penetrator's path and reducing its effectiveness. The Soviet Union was among the first to look into developing reactive armor, beginning in the late 1940s. Although development was slow in the early days of the Cold War and only prototypes were produced, as the importance of this technology became apparent, the Soviets ended up developing some of the first effective ERAs. Their Kontakt-1 and Kontakt-5 systems were widely used on tanks like the T-72 and T-80. These systems were effective against shaped-charge munitions, further enhancing the tank's survivability on the battlefield. During the later Cold War years, the Soviet Union faced significant challenges in the realm of armored warfare. The Western powers, particularly the United States, had developed formidable tanks and anti-tank weapons. Shaped-charge warheads and kinetic energy penetrators had the potential to penetrate traditional armor with ease, making tanks more vulnerable to enemy fire. The Soviet response was to continually innovate and equip its armored vehicles with superior protection. In this context, the development of Explosive Reactive Armor was seen as a crucial step to enhance tank survivability. Soviet engineers developed the Kontakt-1 ERA system in the late 1970s, making it one of the world's earliest ERA implementations. Kontakt-1 ERA is built around the concept of precisely placed explosive blocks layered onto metal plates, arranged in a grid, and attached to the exterior of the tank's hull and turret. When an incoming projectile, such as an anti-tank round or missile, strikes the ERA blocks, the explosives within them detonate. This explosion creates a shockwave and a jet of gas, disrupting the incoming threat. The explosion effectively "pre-detonates" the projectile, diminishing its ability to penetrate the tank's main armor. Kontakt-1 was designed specifically to provide enhanced protection against Western-designed shaped-charge warheads commonly used in US, British, and West German anti-tank munitions. It significantly reduced the probability of successful penetrations, thereby increasing the survivability of the massive Armadas of Soviet armored vehicles. Kontakt-1 ERA was deployed on early Cold War Soviet tanks, including the T-64 and T-72. The introduction of this technology marked a critical advancement in tank protection, as it demonstrated the Soviet Union's commitment to maintaining a strong armored force that could threaten NATO and the West with a quick and powerful armored thrust into the heart of Europe. While the Kontakt-1 was a significant breakthrough, the development of Kontakt-5 ERA represented a further enhancement in tank protection technology. Kontakt-5 refined the fundamental principle of ERA, still including explosive-filled blocks, but introducing some crucial improvements. The most notable of these was the composite structure of the ERA blocks, which incorporated non-metallic materials and metals in specific configurations on top of the standard explosive charges. This innovation provided superior protection against a wider range of threats. The Kontakt-5 also offered enhanced protection against not only shaped-charge warheads but also kinetic energy penetrators, which posed a significant threat to armored vehicles. It was the first type of ERA that was able to significantly decrease the penetration of armor-piercing fin-stabilized discarding sabot (APFSDS) rounds favoured by US and British armored forces. Kontakt-5s also introduced active protective elements. The active element is the explosive component whose concussion and blast can disrupt incoming projectiles. The passive element includes the composite materials and metal plates that form the ERA blocks and are specifically designed to disrupt the projectile upon contact. The combination of these elements makes Kontakt-5s a versatile and effective armor solution against a wide array of anti-tank munitions. Since the early 2000s, the Kontakt-5 ERA has become a standard feature on modern Russian tanks, including the T-80U, T-84, and T-90. These tanks were at the forefront of Russian armored forces during the invasion of Ukraine, and this ERA played a critical role in bolstering their survivability on the battlefield, though the tanks wound up being destroyed through other means, especially top-down exploding ATGMs. Kontakt-1 and later Kontakt-5 ERA systems have had significant impacts on tank warfare, both during the Cold War and beyond. The primary impact has been the enhanced survivability of armored vehicles equipped with ERA. By reducing the effectiveness of incoming threats, ERA has helped tanks withstand anti-tank munitions that would otherwise be disable or destroy the armoured behemoths. The improved protection offered by ERA systems has increased the tactical flexibility of armored units. Tanks equipped with ERA can more confidently engage enemy forces, even in complex and hostile environments where anti-tank threats are prevalent. ERA systems, including Kontakt-5, are particularly effective against anti-tank guided missiles (ATGMs). The disruption caused by the explosive blocks can make these missiles far less likely to achieve a lethal hit on the tank, protecting the armor and its crew from one of the most prevalent anti-tank weapons on the modern battlefield. Explosive Reactive Armor technology has continued to evolve, with subsequent generations offering further improvements in protection against advanced threats. In the context of evolving anti-tank weaponry and changing battlefield dynamics, ERA remains a critical component of tank survivability. As technology continues to advance and new threats emerge, ERA systems will likely continue to evolve, ensuring that armored forces remain a formidable presence on the modern battlefield. The latest development by Russian tank designers includes the Relikt system. Designed by the Russian army in response to new developments in Western ATGM technology and depleted uranium penetrator rounds, Relikt is the 3rd generation of Russian ERA, and is claimed to be twice as effective as its much older brother, the Kontakt-5. It has been installed on some modernized T-72B, T-72B3M, and T-90 tanks after the system was adopted by the Russian army in 2006. Developed by NII Stali, Relikt uses a completely new composition of explosives to achieve dynamic protection. Unlike Kontakt-1, it works equally well against both low-velocity and high-velocity projectiles, reportedly doubling a tank’s protection against shaped charges, and increasing protection against ATGMs by as much as 50 percent. The Relikt system can also reportedly defend against tandem warheads and reduces penetration of APFSDS rounds by over 50 percent. The system was developed in response to the Abrams A3 tank round variant, which was especially effective against Soviet-made ERA-outfitted tanks in the Iraq War. In fact, the A3 round was so effective that the Russian army created Relikt specifically as a countermeasure to the Abrams latest tank round. Supposedly, Relikt is Russia’s most sophisticated tank armor currently in use, and will eventually replace the Kontakt-5 system that is still employed on many older Russian tanks. Kontakt-5 is also still present on some Ukrainian tanks, as well as on Indian T-90S tanks, and on Serbia’s older US-made M-84AS main battle tanks, among others. The latest Russian ERA development, the 4th generation Monolith system (which is often confused with the "Malachit" that was used on the Objekt.187) is still under development, but is expected to be used on later production models of the T-14 Armata. The Armata is also reportedly being built with a new and still classified type of armor, code-named 44S-SV-SH. Little is known about this new alloy, though it is reported to keep its homogeneity in low temperatures, suggesting the Russian government is expecting to use their new tanks in an Arctic environment. It seems many of the ERA developments we’ve listed so far have been a reaction of western developments, specifically the rise in promenance of the Abrams tank. Let’s have a look at what makes this tank a nightmare to take on, and what developments the US has implemented to make the platform almost invincible. The King of Armor: M1 Abrams The M1 Abrams tank, the principal battle tank of the United States, has a storied history of armored protection. Since its inception in the late 1970s, the Abrams tank has evolved significantly in terms of its armor, offering enhanced protection to its crews in a changing battlefield landscape including the renowned Chobham armor and subsequent modern upgrades. The Abrams tank was developed during the height of the Cold War to counter the growing threat of Soviet armored forces. It was named after General Creighton W. Abrams, former Army Chief of Staff and a key figure in the development of post-World War II Western tanks. The Abrams was designed to be an all-around superior tank, with a focus on crew protection, firepower, and mobility. When the Abrams first entered service in 1980, it featured several revolutionary features, including its composite armor. The primary component of this armor was the Chobham composite, a closely guarded secret of British armor technology that combined various materials, including ceramics, metal, and other substances, to achieve superior protection. The Chobham armor was particularly effective in countering the shaped-charge warheads commonly used in anti-tank munitions, giving the Abrams a level of protection significantly higher compared to previous generations of tanks. The Abrams' armor design included both Chobham composite armor and rollled homogeneous steel (RHA) in a modular configuration. This composite armor, combined with the Abrams' steeply inclined front hull and turret, made it exceptionally resistant to various threats, including kinetic penetrators and chemical energy munitions. The Abrams' true test came during the first Gulf War between 1990 and 1991. It was here that the Abrams was first put to the test as it faced off against Soviet-designed tanks such as the T-72 and Iraqi-modified versions, which were equipped with older armor technologies. The Abrams' armor proved to be highly effective, with no Abrams being lost to enemy fire and zero crew losses. The only Abrams that were destroyed fell victim to “friendly fire” from other Coalition forces, or were scuttled by their own crew, rather than allow them to fall into enemy hands. The success of the Abrams in the Gulf War solidified its reputation as one of the most well-protected tanks in the world. While the Gulf War highlighted the effectiveness of the Abrams' armor, it also revealed areas for improvement. Post-war analysis showed that the Abrams' armor could be further improved to make the tank even more impervious to evolving threats. As a result, the US Army initiated a series of armor upgrades. One of the first upgrades involved the installation of depleted uranium (DU) armor inserts. Depleted uranium, a dense and heavy material, was used to reinforce the existing composite armor. This addition improved the Abrams' resistance to kinetic penetrators and increased the protection level of both the hull and the turret. The US also introduced upgrades to the overall armor package, which involved modifying the composition and configuration of the existing Chobham armor. The Abrams played a pivotal role in the U.S.-led invasion of Iraq in 2003. During this conflict, the Abrams faced a variety of threats, including improvised explosive devices (IEDs) and rocket-propelled grenades (RPGs). These unconventional threats prompted the addition of additional armor upgrades. In response to the urban warfare environment of Iraq, the US developed the Tank Urban Survival Kit, or TUSK. This system included various improvements, such as additional armor panels, slat armor for RPG protection, and a remote weapons station. The slat armor, also known as cage armor, was designed to defeat RPGs by detonating them prematurely upon contact with the cage structure. The Iraq War also saw the introduction of reactive armor kits, which were designed to disrupt the penetration of incoming ATGMs. The M1A2 Sep3 Abrams, the most recent upgraded version of the original M1 Abrams, features several enhancements to its armor protection. The Sep3 includes the Abrams Reactive Armor Tile system, known as ARAT. This is similar to the Russian Relikt ERA, but the US version is only applied to the sides of the hull and the turret, and not on the front glacis plate, nor the turret’s front. Modern Armor Systems Ongoing research has led to the development of advanced armor materials, including composite armor, that offer improved protection while reducing weight. These materials have been incorporated into the Abrams' armor configuration to maintain its effectiveness while enhancing overall mobility. More recently, the Israeli army developed the TROPHY system, which creates a neutralization bubble around the vehicle. With special high-tech sensors, it rapidly detects, classifies, and engages all known chemical energy threats, from recoilless rifles and RPGs, to more powerful ATGMs, HEAT tank rounds, and other missiles. To neutralise these threats it, launches an active response explosive that detonates away from the vehicle itself, neutralizing the incoming projectile. Another modern but not so high tech development in tank protection has been documented in the war in Ukraine. The conflict has demonstrated the importance of adaptable and cost-effective armor solutions. Cage armor, often referred to as "slat armor," has gained prominence in response to the threat of anti-tank guided missiles (ATGMs) and RPGs used by close-in infantry. However, these cages proved ineffective when matched against US-made ATGMs like the Javelin, which sports a two-part, top-down attacking warhead. Russian tanks are particularly vulnerable to such attacks, as their design incorporates an autoload feature that stores ammunition on the floor of the turret. Penetrating a T-72, T-80 or T-90 from the top often means the tank literally blows its turret clean off as the ammo in the autoloader blows up. Burned-out Russian tanks with turrets lying dozens of yards away have become a common sight on the Ukrainian war zone. In an attempt to counter such attacks, Russia has employed the euphemistically named “cope cages,” which are nothing more than additional slats or fences on top of their turrets. These have proved almost useless against top-down ATGMs. Late in September 2023, a few Russian tanks were spotted with cope cages now displaying ERA systems on top. There’s no word yet on whether these DIY solutions will protect Russian tanks from increasingly accurate Ukrainian drone attacks. But these cope cages must be at least somewhat effective since they've been spotted on Israeli tanks in their October 2023 fighting near the Gaza strip. There have also been attempts to counter one of the most lethal threats on the Ukrainian battlefield: drones. Russia has tried to counter these low-tech threats by wrapping netting around their tanks, with the hope that the small drones would get tangled and explode far enough away from the tank as to not damage it. But unless a tank uses netting that covers 100% of a tank’s vulnerable areas, this method of tank protection won’t be effective: modern drones are so highly maneuverable that it only takes a small gap in this netting for them to make it past the makeshift protection and deliver a deadly blow to the tank and its crew. It should be noted that many Russian tanks have been defeated by small drones carrying grenades and occasionally payloads as heavy as an anti-tank mine, which they then drop down a Russian tank’s open hatch. Of course, Russian troops could rectify this problem by simply keeping their hatches closed, but this is often not practical a practical solution as it greatly limits the visibility of the crew inside. It’s not just the Russians that have been innovating on the fly, the Ukrainian military, faced with limited resources and a need for effective countermeasures, have developed their own variations of cage armor. These cage armor configurations have been installed on various armored vehicles, including older tanks like the Soviet-era T-64 and T-72, as well as on infantry fighting vehicles and armored personnel carriers. Their effectiveness, like their Russian counterpart, is also questionable though. Let’s move away from these more primitive forms of tank protection and look at perhaps the most advanced protection systems ever used on tanks. They’re called APS, or… Active Protection Systems As technology advances, so does the potential for more advanced protection systems. One of the latest of these innovations is the Active Protection Systems, which is designed to intercept and neutralize incoming threats, such as anti-tank guided missiles, before they reach the tank. The Israeli Trophy is such a system, while Russia is designing a similar system called Arena, which has yet to reach production or to have been installed on any more than a handful of showroom tanks. Once again, Russia led the way with this kind of technology, starting in the late 1970s and into the 80s and 90s with their first-of-a-kind APS systems. The first APS they developed was the Drozd in late 1977 which was used throughout the Soviet war in Afghanistan, eventually being replaced in 1982. This system featured a millimeter band radar that would activate rockets attached to the turret which would intercept projectiles heading towards the tank. As well as the previously mentioned Arena system, Russia is also fielding an APS called Afganit on their T-14 Armata tanks. This system uses a small Doppler radar and electro-optical sensors in both ultraviolet and infrared bandwidths to track incoming targets, which are then intercepted by the system. This isn’t the only cuttnig edge piece of protection tech being developed, though. Research is also ongoing in the field of electromagnetic armor, which uses electromagnetic fields to deflect or disrupt incoming projectiles. While still in its early stages, this technology holds promise for future tank protection, though its cost – including an expensive power source – may make it prohibitively expensive to field in any large numbers. With any luck, we might see this futuristic forcefield like technology go against the Russian’s primitive “cope cages” if the conflict in Ukraine escalates and the US decides to stop pulling its punches and finally send over its UFO tech to Ukraine. Now check out “Why US Enemies Are Scared of AbramsX (Next Generation Tank)”. Or watch “Why Russian T-90 Tank Absolutely SUCKS”!