Tank destroyer

A self-propelled anti-tank gun, or tank destroyer, is a type of armoured fighting vehicle. Tank destroyers are used primarily to provide antitank support in combat operations but do not fit all the criteria of a tank. They may mount a high-velocity anti-tank gun but have an open turret, no turret at all or run on wheels instead of tracks. Vehicles which carry an antitank guided missile launcher are referred to as ATGM carriers.

Tank destroyers cannot fulfil the many roles of tanks; they are much less flexible, and usually lack a strong anti-infantry capability. A common feature of a tank destroyer is the absence of a turret, and compared to tanks, an even stronger disposition for heavy frontal armor (compared to side and rear armor). However, as a result of having no turret and fewer parts, tank destroyers are much less expensive to manufacture.

Gun-armed tank destroyers have been largely supplanted by the more general-purpose tanks since World War II, but lightly-armoured ATGM carriers are used for supplementary long-range antitank capabilities.

World War II

Soviet ISU-122 tank destroyer with Polish Army markings

Dedicated antitank vehicles made their first major appearance in the Second World War, as combatants developed effective armoured vehicles and tactics.

These tank destroyers fell broadly into two categories. Some were designed to be faster and cheaper than medium tanks while still able to destroy heavy armour at long range. Some of these designs were clearly expedients rushed into production. The second design strategy was to create heavily-armoured vehicles that were more effective in tank-versus-tank combat than enemy tanks.

German designs

The first German tank destroyers were the Panzerjäger ("tank hunters") which took an existing anti-tank gun and put it on a convenient chassis to give mobility. For instance, the German Panzer I light tank was obsolete before the war even started, with only thin armor and machine guns for armament. It was put into battle during the invasion of Poland, where it was found to be a deathtrap. Before the subsequent invasion of France, 202 were rebuilt as the Panzerjäger I self-propelled Skoda 47 mm anti-tank guns taken from Czechoslovakia. Similarly Panzer II tanks were used during Operation Barbarossa; captured Soviet 76.2 mm anti-tank guns were mounted on Panzer II chassis, producing Marder II anti-tank guns. The most common mounting was a German 75 mm anti-tank gun on the Czech Panzer 38(t) chassis to produce the Marder III. The Panzerjäger series continued up to the 88 mm equipped Nashorn.

Although the Panzerjager carried effective weapons they were generally lacking in protection for the crew having thinly armoured open-topped superstructures and used older designs of chassis. They were to be followed by the Jagdpanzers '("hunting tanks") which mounted the gun in better superstructures – sacrificing the wider traverse capability of the anti-gun carriage for good armour protection. The best of the designs is considered to be the Jagdpanther which put an 88 mm gun in one of the later tank chassis, that of the Panther tank. The Germans became side-tracked into production of large numbers of tank-destroyers because they could be produced more cheaply than full tanks. The Jadgpanzers were better suited to defense than attack because of their limited traverse and the later designs such as the Jagdtiger (of which just under 50 were built by May 1945) were heavy and consequently less manoeuvrable albeit extremely hard to defeat.

The most effective German tank destroyer by far was one that was not supposed to be one: the Sturmgeschütz III.

Soviet

As with the Germans, the Soviet designs mounted anti-tank guns, with limited traverse in turretless hulls. The results were smaller, lighter, and simpler to build than tanks, but could carry larger guns. This design methodology was used by both the USSR and the Germans to provide heavier anti-tank capability at lower cost, during the rapid up-armoring of all AFVs that took place during the war. The Soviets produced the 85 mm SU-85 and 100 mm SU-100 self-propelled guns based on the same chassis as the T-34 medium tank, as well as the 122 mm ISU-122 and 152 mm ISU-152 which shared components with the IS-2 heavy tank and was nicknamed Zveroboy ("beast killer") for its ability to destroy German Tigers, Panthers and Elephants. In 1943, the Soviets also shifted all production of light tanks like the T-70 to much simpler and better-armed SU-76 self-propelled guns, which used the same drive train.

US Army tank destroyer doctrine

U.S. Army and derivative British designs were very different in conception. U.S. doctrine was based on the perceived need to defeat German blitzkrieg tactics, and U.S. units expected to be faced with large numbers of German tanks attacking on relatively narrow fronts. In actual practice, such attacks rarely happened. The Tank Destroyer Command eventually numbered over 100,000 men and 80 battalions equipped with 36 tank destroyers each. Some TD battalions were later organized into Groups of 3 to 5 battalions with other battalions being attached to infantry divisions.

The U.S. tank destroyer designs were intended to be very mobile and heavily armed. Most retained a turret, but left it open on top both to save weight and to accommodate a larger gun. The earliest expedient design was an M3 Half-track mounting an M1897 75 mm gun in a limited-traverse mount, and called the 75-mm GMC M3. Another, and considerably less successful early design mounted a 37-mm antitank gun in the bed of a Dodge 3/4-ton truck -- the 37-mm GMC M6. The larger guns required a counterweight at rear of the turret, which can be seen on designs like the 3-inch gun 3in Gun Motor Carriage M10 and the 90mm Gun Motor Carriage M36. The 76mm Gun Motor Carriage M18 came closer to the U.S. ideal; the vehicle was very fast, small, and mounted a 76 mm gun in a turret. Of these, only the 90 mm gun of the M36 proved to be effective against the Germans' larger armored vehicles. The open top made these Tank Destroyers particularly vulnerable to anything from ordnance such as an artillery shell or a hand grenade to even the elements, which reduced fighting crew capability. To compensate this they had a collapsable roofkit. Further, the light armor of Tank Destroyers proved to make them the far more vulnerable targets in encounters with their intended prey. By 1943, the very idea of independent anti-tank groups was deemed to be unworkable and no further US Tank Destroyer battalions were created. For the rest of the war, existing TD units found use as self-propelled artillery and assault platforms against "soft" targets.The M36 Jackson (apart from the M26 Pershing, which was only available in small numbers) was the only American vehicle capable of knocking out the German heavy tanks at a distance.

United Kingdom

On the whole, the British army did not subscribe to the Tank Destroyer concept, preferring instead to design tanks armed with bigger guns. Although flawed in many other respects, contemporary British armour doctrine recognized the inevitability of tank versus tank combat and the Army strove to arm their tanks with the most powerful anti-tank gun available at the time.

Anti-tank guns were the domain of the Royal Artillery rather than the Tank Corps and anti-tank gunned vehicles particularly anti-tank self-propelled guns such as the Deacon and Archer were their preserve.

The self-propelled guns that were built in the "Tank Destroyer" mould came about through the desire to field the formidable QF 17 pounder anti-tank gun and simultaneous lack of suitable tanks to carry it. As a result they were of a somewhat extemporized nature as a result. Mounting the gun on the Valentine tank chassis gave the Marder-like Archer. The 17 pounder was also used to equip the US supplied M10 Wolverine to produce the Achilles. Another attempt to produce a specialist anti-tank vehicle was to fit the 17 pounder to the Cromwell chassis to give Tank, Cruiser, Challenger (A30) and its near open-topped variant Avenger. The latter delayed until post war before entering service.

The closest the British came to developing an armoured Tank Destroyer in the vein of the German Jagdpanzers or Russian ISU series was the Churchill 3 inch Gun Carrier - a Churchill tank chassis with a boxy superstructure in place of the turret. The design was rejected in favor of developing a 17 pounder armed Cromwell tank variant ultimately leading to the Comet tank

By 1944, a number of the "basic" Shermans in British use were being converted to Sherman Fireflies by adding the potent QF 17 pounder gun — giving each platoon of Shermans a dedicated anti-tank tank.

Post–World War II development

In the face of the Warsaw Pact, a general need for extra firepower was identified. In the 1950s, the UK produced the FV 4101 Charioteer to beef up the tank regiments, mounting a 20 pounder gun in an oversize turret on the Cromwell tank hull — it lacked the all round capability of the Centurion tank. It was followed by the Conqueror tank which carried a 120 mm gun. In the late 1960s, Germany developed the Kanonenjagdpanzer, essentially a modernized WWII Jagdpanzer mounting a 90 mm gun. As Soviet designs became more heavily armoured, the 90 mm gun became ineffective and the Kanonenjagdpanzers were retrofitted for different roles or retired.

With the development of flexible Anti-tank guided missiles, which were capable of installation on almost any vehicle in the 1960s, the concept of the tank destroyer has waned. With the weight of main battle tanks growing to the forty to seventy-tonne range, airborne forces were unable to deploy reasonable antitank forces. The result was a number of attempts to make a light vehicle, including the conventional ASU-85, the recoilless rifle–armed Ontos, and missile-armed Hornet Malkara armoured car and Sheridan light tank.

Modern tank destroyers

Many forces' IFVs carry ATGMs in every infantry platoon, and attack helicopters have also added antitank capability to the modern battlefield. But there are still dedicated antitank vehicles with very heavy long-range missiles, and ones intended for airborne use.

A Norwegian antitank platoon equipped with NM142 TOW missile launchers

There have also been dedicated antitank vehicles built on ordinary armoured personnel carrier or armoured car chassis. Examples include the U.S. M901 ITV (Improved TOW Vehicle) and the Norwegian NM142, both on an M113 chassis, several Soviet ATGM launchers based on the BRDM reconnaissance car, and the German Raketenjagdpanzer series built on the chassis of the HS 30 and Marder IFV.

A US Army mechanized infantry battalion has four infantry companies with TOW missile–armed Bradley IFVs and can bring a large concentration of accurate and lethal fire to bear on an attacking enemy unit that uses AFVs.

Missile carrying vehicles however are referred to as ATGM (Anti-Tank Guided Missile) carriers instead of tank destroyers. In modern times a tank destroyer is an armored fighting vehicle with a large caliber cannon which is not a tank because it does not fit into all the criteria that makes a tank a tank. A tank is an armored vehicle which runs on tracks and has a large caliber cannon in a 360 degrees rotatable enclosed turret. This makes large caliber gun vehicles that have an open turret (M36 Jackson), do not have a turret (STRV-103, Kanonenjagdpanzer) or which run on wheels instead of tracks (Centauro, PTL02) tank destroyers.

Some gun-armed tank destroyers continue to be used. The German army had specialized Kanonenjagdpanzer, similar in design to the WWII tank destroyers, from the mid-1960s until the 1980s. In the same timeframe, Sweden developed armoured forces: the STRV-103, armed with a 105 mm cannon (however its actual combat role is uncertain). The People's Republic of China has developed the PTL02 tank destroyer. This wheeled assault tank destroyer armed with a 100 mm rifled gun was developed by NORINCO for the PLA new light (rapid reaction) mechanised infantry divisions. The vehicle has a three-man turret derived from the Type 88 MBT, and a 6×6 wheeled chassis based on the WZ551 APC. Italy and Spain use the Italian-built Centauro, a wheeled tank destroyer with a 105 mm cannon. The gun-armed tank destroyer may possibly see revival in the US Army through the introduction of the Stryker, more specifically, the M1128 Mobile Gun System, a Stryker variant armed with a 105 mm cannon which has remote control and autoloading capabilities.

Ironically, modern tank destroyers, due to being more mobile than tanks, are more suitable for low-intensity and urban warfare that are being fought in the War on Terrorism. Some are considering the possibility of replacing tanks with lightweight, wheeled tank destroyers to deal with elusive insurgents encountered in both Iraq and Afghanistan. For instance, the Canadian Forces had considered replacing their aging Leopard I tanks with the Stryker Mobile Gun System, essentially creating a tank destroyers-only force.

References

• Harry Yeide, (2005) The Tank Killers: A History of America's World War II Tank Destroyer Force. Havertown, PA: Casemate. ISBN 1-932033-26-2