Explosive Reactive Armor

Shaped charge weapons were developed starting with World War Two to provide an infantry portable anti-armor weapon.  European and American ordnance scientists worked on this problem for years, at first intuitively feeling that the phenomenon called the Munroe Effect offered promise.  Initially shaped charge weapons were deployed in 1940 as hand grenades and subsequently as rifle grenades and rocket propelled grenades.  Post World War Two development enhanced the effectiveness of the shaped charge weapon, and increased the range and accuracy of the delivery systems.

The armor versus weapon race has been run since the advent of the armored fighting vehicle.  Advances in armor protection initiated a round of development in armor defeating weapons, which in turn heated up the development of armor to defeat these weapons.  The photos below, linked from the Panzerfaust website, illustrate typical measures the Red Army took to defeat German shaped charge weapons. 

(If you have difficulty with these images, right click, and then click on "show picture".)

Wire mesh screens on a T34-85.

Schurtzen-type steel plates on a JS-122.

Following World War Two, ordnance pundits stated that the tank was rendered little more than a battlefield target for the shaped charge equipped antitank guided missile.  Armor developers and engineers were not so quickly dismayed, however, and advances in shape, composition, and spacing of armor began to reduce the battlefield impact of the ATGM.   With each advance in armor protection, the size and penetration capability of the shaped charge weapon was increased.  Chobham Armour was introduced in the latter decades, achieving reasonable protection from contemporary shaped charge and kinetic energy projectiles.  

Scientists and engineers also sought alternatives to armor composition.  Early 1970's Dr. Manfred Held, of MBB in Germany, invented a device called a drive-plate explosive sandwich. This device is composed of two metal plates separated by a layer of explosive. As currently deployed on armored fighting vehicles, this reactive armor assembly consists of sheets set at an oblique angle with respect to the anticipated axis of attack.

The concept of operation is relatively straight forward.  The shaped charge warhead creates a high-speed molten jet from the explosive collapse of its internal cone.  This jet perforates the outermost steel plate in the sandwich and ignites the explosive layer. As the explosive layer detonates, its detonation pressure forces the metal sheets apart.  Because the metal sheets are set at an angle oblique to the axis of the shaped charge jet, the flying plate continuously feeds new armor material into the path of the penetrator jet, deflecting it (called perturbation) and consuming its energy.  A shaped charge jet, attenuated and perturbed in this manner, prematurely particulates or decomposes into a series of independent and unaligned fragments.  Additionally, the movement of the outer plate introduces a non-perforated metal sheet ahead of the slower moving shaped charge slug.  This slug has insufficient penetrating power to break through the plate.  Finally, the distance between the AFV armor and the point of contact increases the stand-off distance, further decreasing the penetration capability of the shaped charge jet.  The net result is that the shaped charge weapon cannot achieve a significant penetration of the AFV main armor.

Explosive Reactive Armor Pros and Cons

The use of explosive reactive armor offers substantial advantages along with some significant problems.  Beyond the protection performance advantage the ERA sandwich can be easily retrofitted onto existing main battle tanks as well as designed into new manufacture.  This armor makes newer tanks extremely survivable, and breathes new life into some obsolescent vehicles. 

ERA armor plate sandwiches are usually called bricks.  Fitting these ERA bricks adds significant weight to main battle tanks, generally no more than 1.5 tons to the overall weight of the vehicle.  While many MBTs are able to take on the extra tonnage without any serious degradation of mobility, the suspensions of several tanks are inadequate to this burden.

Another disadvantage is the function of the reactive armor itself, particularly the secondary effects (blast and fragmentation) on gun optics or nearby personnel. Field and proving ground tests prove that ERA cannot be set off by vibration, impact of small arms rounds, fire, or sympathetic detonation from the detonation of a nearby ERA brick.  However, detonation of a brick near the main gun sight may render it inoperative.  Detonation also creates a blast and fragmentation risk to close-by infantry or to any exposed crew such as the tank commander.

Typical Deployment

Probably the most extensive deployment of explosive reactive armor has been the fitting of BLAZER armor onto the Israeli Defense Force main battle tanks. The Israelis have developed an impressive type of ERA called BLAZER armor, and they continue to develop and improve its ERA, applying lessons learned from the field as well as from training maneuvers and experimentation.

The Russians observed the performance of BLAZER armor in the Israeli 1982 Lebanon campaign.  They subsequently embarked on a development program and deployed ERA to a number of main battle tanks. The T-72 can be retrofitted with ERA, and the T-80U has integrated reactive armor on its front slope and turret.  Other tanks and vehicles can be retrofitted as need and resources dictate.

US Marine Corps M60A1s were deployed during the Gulf War bearing ERA appliqué bricks. The large bolts on the sides of the Bradley Infantry Fighting Vehicles can be used to apply ERA blocks.

Back to the Gun versus Armor Race:  How to Defeat ERA

With increasing deployment of ERA, there have been numerous attempts to compensate and nullify  the advantages offered by this technology.  An interesting and promising approach is the use of dual, compound, or tandem warhead rounds and missiles.  Tandem rounds are simple in concept:  the weapon consists of two (or more) shaped-charged warheads, deployed along a single axis, one in front of the other.  The first warhead, termed a precursor charge (PC) is slightly smaller than the main charge. This precursor charge impacts on the ERA and detonates the brick. After a very minimal time delay, the energy and motion of the ERA has dissipated, and the main charge (MC) detonates.  Its jet passes through the plates, sometimes through the hole created by the PC, unimpeded by the protective mechanism of the reactive armor.

In Conclusion

Since its deployment in the early 1980s by the IDF, Explosive Reactive Armor has gained a wide popularity despite its ungainly appearance.  Its advantages have been shown in combat, in the Middle East and South West Asia.  It has been proven to be a safe, reliable, and extremely effective method of minimizing the effects of shaped-charge anti-tank warheads. It is now deployed by numerous countries on many and various types of armored fighting vehicles. The R&D effort for both ERA enhancement and shaped charge weapon improvement continues - barring a major technological leap by the shaped charge designers, the ERA will remain a highly effective supplemental armor used to retrofit and extend the life of older vehicles, and improve the protection of contemporary and newer designs.


Bolte, Phillip L. "Tank Survivability on the Modern Battlefield." International Defense Review Supplement, 8/1985.

Crawford, Major S. W. "The Main Battle Tank: Future Developments - A British Perspective." Armor. January/February 1993.

Delamain, Charles. "Armor for the Modern Battle Tank." Tank Journal. May 1990.

Schwartz, Wolfgang. "Explosive Reactive Armor: How it works and How to Defeat It." Military Technology. 8/91.

Vered, G.R. "Evolution of BLAZER Reactive Armor and Its Adaption to AFVs." Military Technology. 12/87.

A Table Top Tactics Article.

  Copyright © 2001 by Mark Diehl.  All rights reserved.