Gulf War and the M1 A1 Abrams Main Battle Tank (Part 5)
DU, which is an economical material with a cost of approximately USD 30 per kilogram, has significantly increased the combat effectiveness of the tank by exhibiting a superior performance in absorbing the energy of the bullets hitting the armour and preventing them from penetrating thanks to its high density.
In the previous part of this series, the remarkable performance of the M1A1 HA Abrams main battle tank in the Gulf War, its technological superiority and the highly effective ammunition it uses were analysed in detail. In particular, the superior ballistic performance of the M829A1 armour-piercing ammunition against the Soviet-made T-72 tanks of the period and the M1A1's ability to use various types of ammunition suitable for different operational requirements were highlighted. In addition, the fact that the T-72 tanks in the Iraqi Army's inventory are at a lower technological level compared to the M1A1 and use older generation ammunition was evaluated as a factor that significantly affects the success of the M1A1 Abrams on the battlefield.
The relevant section can be accessed from the link below.
Gulf War and the M1 A1 Abrams Main Battle Tank (Part 4)
The cover photo shows an M-1A1 Abrams main battle tank (with forest green camouflage pattern) travelling with a convoy on a desert road during Operation Desert Shield.
What were the main reasons for the success of the M1A1 Abrams in the Gulf War?
1) Firepower and Ammunition; To examine this issue in more detail, you can take a look at part 4 of our article series.
2) Armour Technology and Protection Level
M1A1 Abrams: Uses laminated armour technology instead of homogeneous steel armour. This is a type of armour created by combining different materials in layers. The M1A1's armour provides high protection against APFSDS rounds and HEAT rounds. In the M1A1 HA model, armour protection has been further strengthened. The armour of the M1A1 is designed to be thicker in the front and thinner in other areas. It would be appropriate to elaborate a little more on this subject.
Depleted Uranium (DU) Armour Integration; The armour configuration of the M1A1 Abrams main battle tank has been significantly improved with the modifications implemented especially since May 1988, increasing its survivability against kinetic energy (KE) penetrators and chemical energy (HEAT) warheads. An important part of this modernisation is the integration of depleted uranium (DU) armour, which started with the M1A1 HA (Heavy Armour) variant and emerged as a reflection of the US strategy to increase the firepower and survivability of main battle tanks during the Cold War.
The DU armour layer, which was included in the production line of M1A1 tanks as of May 1988, was integrated into the existing turret armour. Attenuated uranium, a by-product of the nuclear fuel production process, is an isotope of uranium with lower radioactivity that remains after the ‘enrichment’ process of natural uranium ore. This enrichment process isolates the more radioactive isotope uranium-235 so that uranium can be used in nuclear weapons or reactors. Although attenuated uranium has radioactive properties, it does not pose a significant health risk from external exposure. However, as stated by the US Environmental Protection Agency (EPA), it is known that if attenuated uranium is ingested or inhaled, it can directly damage living cells due to the gamma particles it emits and may adversely affect kidney function in particular.
With a density about 1.7 times higher than lead and about 2.5 times higher than steel, DU, combined with its pyrophoric properties, provides exceptional resistance to KE penetrators. DU, which is an economical material with a cost of approximately USD 30 per kilogram, has significantly increased the combat effectiveness of the tank by exhibiting a superior performance in absorbing the energy of the projectiles hitting the armour and preventing them from penetrating thanks to its high density. This provides effective protection against kinetic energy penetrators such as armour-piercing APFSDS ammunition. This modification has made the M1A1 Abrams tank a combat platform with superior armour protection that remains effective today.
Second Generation DU Armour and M1A1HA+ Configuration: In subsequent production versions of the M1A1HA (Heavy Armour) variants, the Second Generation DU Armour Package (Second Generation DU Armour Package) was used. Vehicles with this improved configuration are designated as M1A1HA+. Although the detailed composition of the second generation DU armour is not publicly available, it is thought to have a more advanced matrix structure and possibly a different DU alloy compared to the first generation DU armour. This means a higher level of protection.
Details of Armour Architecture: The armour architecture of the M1A1 series tanks is classified as "composite armour ’ and consists of a combination of multiple layers. The term ‘resin-bonded ceramic blocks between conventional armour layers’ describes a key feature of this composite structure.
Ceramic Elements and Interaction Mechanism: In the internal arrangement of the armour, ceramic blocks are resin-fixed within a matrix structure. The main function of these ceramic elements is to absorb and dissipate the energy of the projectile by deforming upon impact with an anti-tank projectile (especially a KE penetrator or HEAT warhead). Despite its high hardness, ceramic exhibits a brittle behaviour under impact. This fracture process leads to the conversion of some of the projectile's energy into heat and the destruction of the integrity of the projectile.
Microparticle Cloud and Erosion Effect: According to some analyses in defence publications, when anti-tank shells hit ceramic blocks, these blocks shatter and form a cloud of small and hard particles with high velocity. These particles spread in the space in front of the projectile, hitting the projectile itself and causing erosion at the tip of the projectile. This erosion reduces the ability of the projectile to penetrate subsequent layers of armour and increases the overall effectiveness of the armour. This mechanism is particularly effective against long rod penetrators (LRP).
Backing Plate: The special armour compartment in which this armour system is integrated is called the ‘backing plate’. The backing plate holds the ceramic blocks and other armour layers in place and ensures structural integrity. It also helps to prevent the penetration of energy and particles into the tank interior caused by the breakage of the ceramic blocks.
M1A1 Abrams: The M1A1's armour provides a high level of protection against APFSDS and HEAT rounds from the front. According to the information given in the sources, the frontal armour of the M1A1 provides 600 mm protection against APFSDS projectiles and 700 mm RHA (Rolling Homogeneous Armour) thickness equivalent protection against HEAT projectiles. In the M1A1 HA model, turret armour provides 800mm protection against APFSDS projectiles and 1300mm RHA protection against HEAT projectiles.
M1A1 Abrams: The M1A1 has most of its ammunition in a protected compartment behind the turret. This design minimises the risk of hitting the ammunition inside the tank and, in the event of an explosion, prevents the explosion from affecting the crew. Thanks to the special blast panels on the roof behind the turret of the M1A1, even if the ammunition explodes, the blast energy is directed upwards, increasing the crew's chances of survival. In order for this design to be activated, the cover of the ammunition storage area must be closed in the event of a hit on the turret.
Explanations on the above table
RHA Equivalent: The values given in the table indicate how much thick homogeneous steel armour equivalent protection the armour provides against a given threat. So, for example, 600 mm RHA protection of the hull of the M1A1 against APFSDS projectiles means that this armour is as effective as 600 mm thick homogeneous steel armour. However, this is only a benchmark, as modern tank armour is composed of composite materials much more complex than homogeneous steel.
APFSDS (Armour Piercing Wing Stabilising Sabot): These projectiles penetrate armour with their high velocity and kinetic energy. They are usually made of high-density metals such as tungsten or diluted uranium.
HEAT (High Explosive Anti-Tank): This ammunition penetrates armour using the high-temperature metal jet generated by the explosion.
T-72 Series: Soviet/Russian-made main battle tanks. The table shows the protection levels of different variants (T-72, T-72M, T-72M1, T-72B1). Especially T-72B1 has higher protection levels compared to other variants thanks to its more advanced armour.
M1A1 and M1A1 HA: They are variants of the American-made M1 Abrams tank. The M1A1 HA (Heavy Armour) has significantly increased protection, especially in the turret. The major difference in its protection against HEAT ammunition is striking. This difference is probably due to the use of armour reinforced with depleted uranium.
Comparison: The table shows that the M1A1 and especially the M1A1 HA variants have significantly higher levels of protection compared to the T-72 series tanks. This is an important factor that increases the survivability of the M1 Abrams tank on the modern battlefield.
Armour Technology and Protection Level of T-72 Main Battle Tank
T-72 tanks used laminate armour, also known as composite armour. However, export versions, especially the T-72M1, did not always have the most advanced armour technologies used in the Soviet army. This resulted in export models generally having lower levels of protection.
Early Versions: Early versions of the T-72 used laminated armour on the front armour plates, while the turret used conventional cast steel. Laminated frontal armour consists of layers of high carbon steel, glass reinforced plastic and high carbon steel again. Although this structure provides a certain advantage over homogeneous steel armour, it is insufficient to provide adequate protection against modern threats. The turret armour, on the other hand, was initially made of cast steel, but was upgraded with ceramic rods in later versions.
T-72M1 and Export Models: The T-72M1 model used by countries such as Iraq was inferior to the armour of the Russian army's best T-72B tank at the time. In T-72M1 tanks, armour reinforcement was made by using ceramic rods in front of the turret. However, this improvement did not provide protection equivalent to the more advanced composite armour technology of the T-72B. In general, the armour of the T-72 tanks was designed to be thicker at the front. This is intended to better protect the tank against threats from the most likely direction of attack.
Level of Protection and Resistance to Threats: The T-72's armour has a lower protection level than the American M1A1 Abrams tank. For example, the frontal armour of the T-72M1 provides approximately 400mm RHA (Rolled Homogeneous Armour) equivalent protection against APFSDS (Armour Piercing Wing Stabiliser Sabot) rounds, and approximately 490mm RHA equivalent protection against HEAT (High Explosive Anti-Tank) rounds. This means that the T-72M1 is more vulnerable to more powerful weapons such as the M1A1's 120mm cannon. The T-72 is generally designed to withstand the steel APFSDS shell of a 115mm Soviet tank gun. The T-72M1, on the other hand, can offer some resistance to advanced threats such as the Israeli 105mm M111 APFSDS of the early 1980s. However, its effectiveness against modern anti-tank weapons is limited. The side and rear armour of the T-72s provide less protection than the front armour and are more susceptible to attack from these areas.
Automatic loaders are used in T-72 main battle tanks. Tanks with this system do not require a crew to load ammunition. Image source Washingtonpost newspaper.
Ammunition Storage and Risk of Explosion: On T-72 tanks, 22 of the 44 rounds of ammunition are stored in a rotating ammunition carousel under the turret floor. This design is intended to minimise the internal volume of the tank and increase automation. However, this significantly increases the likelihood of the ammunition exploding and the tank being completely destroyed in the event of an armour penetration. The amount of propellant carried by the T-72 is twice that of the T-55 (440kg versus 220kg), which further increases the tank's propensity to explode. For this reason, T-72s can experience explosions known as the ‘Jack in the box effect’ / ‘ Turret ejection’ / ‘Cap throw’ when their armour is penetrated, resulting in their turrets being blown up. This is an important factor that negatively affects the survivability of T-72 tanks on the battlefield.
In summary, although the T-72 tank has different armour configurations in different versions, it generally has a lower level of protection compared to modern Western tanks. In particular, the location of the ammunition storage brings with it the risk of a major explosion if the tank's armour is penetrated.
The M1 Abrams main battle tank has demonstrated superior survivability in combat conditions in Iraq. Although the M1A1 variant took direct frontal hits from Iraqi T-72 tanks, minimal damage reports confirm the high survivability of this tank. During Operation Desert Storm, M1 Abrams tanks were hit by armour-piercing munitions, including kinetic energy penetrators, on six separate occasions, but maintained armour integrity and no armour penetration incidents were recorded.
One of the important factors that enables the M1 Abrams main battle tank to perform superiorly in the harsh conditions of the modern battlefield is the modular structure of the advanced armour system. This modularity allows the tank's armour configuration to be adapted to different types of threats that may be encountered. The modular armour system allows for quick and easy replacement of damaged armour panels in the field, increasing the sustainability of the tank's combat effectiveness. In addition, the tank's protection level can be optimised by integrating different armour packages against different threat levels. For example, a more effective armour configuration can be preferred against anti-tank rockets in urban area operations, while a configuration that is more resistant to kinetic energy-piercing ammunition can be used in conventional combat scenarios. This adaptability has made the M1 Abrams an effective combat platform in a wide range of operational environments.
