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Tank Destroyer

A self-propelled anti-tank gun, or tank destroyer, is a type of armored fighting vehicle designed specifically to engage enemy armored vehicles. Many have been produced as a tank-like vehicle, but with light armor and capable of higher speed, with a gun or missile launcher. Many lack turrets. Aiming in the horizontal plane is achieved partially by maneuvering the entire vehicle in the turretless models, with final fine adjustments possible using a limited-traverse gun mount.

Tank destroyers are used primarily to provide anti-tank 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 anti-tank guided missile launcher are also referred to as ATGM carriers.

Gun-armed tank destroyers had been largely replaced by the more general-purpose main battle tanks since World War II, but lightly-armored ATGM (anti-tank guided missile) carriers are used for supplementary long-range anti-tank capabilities. Modern tank destroyers primarily rely on missiles instead of guns to destroy tanks. However the needs of expeditionary warfare in the past decade has seen the recreation of lightweight gun armed, sometimes called protected gun systems, tank destroyers.

Strengths and weaknesses

The use of a fixed or casemate superstructure in place of the rotating turret found on normal tanks (except for almost all American WW II designs) confers both strengths and weaknesses upon the tank destroyer. Dispensing with the turret makes tank destroyers significantly cheaper, faster and easier to manufacture than tanks. Tank destroyers can also be fitted with larger superstructures, allowing accommodation of a bigger cannon than could be mounted in a turreted tank on the same chassis, and increasing the vehicle's internal volume, allowing for increased ammunition stowage and crew comfort. Eliminating the turret also allows the vehicle to carry thicker armor than would otherwise be the case.

But tank destroyers cannot fulfill the many roles of tanks; they are much less flexible, and their guns are often optimised for defeating armour at the expense of anti-personnel capability. A common feature of a tank destroyer is the absence of a turret, and in some designs, stronger frontal armor. Use of open-topped hulls was problematic since it afforded the tank destroyer crew less protection, both from high explosive weapons and nuclear, biological, and chemical threats. Turretless tank destroyers are most often used in concealed ambush positions where they can wait for a target to enter their line of fire. They are thus better suited to tactical defense rather than offensive usage.

Tank destroyers of World War II-vintage quickly became obsolete after the war as main battle tanks (MBTs) became more capable.

World War II

Dedicated anti-tank vehicles made their first major appearance in the Second World War, as combatants developed effective armored 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 armor at long range. The second design strategy was to create heavily-armored vehicles that were more effective in tank-versus-tank combat than enemy tanks.

Polish designs

The first dedicated tank destroyers were two models of TKS Polish tankettes with 20mm (24 vehicles) and 37mm guns (2). They suffered heavy losses during the invasion of Poland before entering battles due to air bombardment, penetrating their weak top armor.

German designs

The first German tank destroyers were the ''Panzerjäger'' ("tank hunters") which took an existing anti-tank gun and mounted it on a convenient chassis to give mobility, usually with just a three-sided gun shield for protection. For instance, 202 German Panzer I light tanks were modified by removing the turret and were rebuilt as the Panzerjäger I self-propelled Skoda anti-tank gun. Similarly, Panzer II tanks were used on the eastern front. Captured Soviet anti-tank guns were mounted on modified Panzer II chassis, producing the Marder II self-propelled anti-tank gun. The most common mounting was a German anti-tank gun on the Czech Panzer 38(t) chassis to produce the Marder III. The Panzer 38(t) chassis was also used to make the Jagdpanzer 38 'Hetzer' casemate style tank destroyer. The Panzerjäger series continued up to the equipped Nashorn.

Although the Panzerjager carried more effective weapons than the tanks on which they were based, they were generally lacking in protection for the crew, having thinly armored open-topped superstructures. They were to be followed by the ''Jagdpanzer'' '("hunting tanks") which mounted the gun in better, true casemate-style superstructures. This was the case with the Jagdpanther, considered the best of the casemate-design Jagdpanzers,Forty and Livesey 2006 p. 33 which put an gun in the later, mid-World War II Panther tank's chassis, originally designed to use a 75mm cannon in a turreted mount. The Jagdtiger was the heaviest German armored fighting vehicle to go into active service. German tank destroyers based on Panzer III's or later tanks were unique in that they had more armor than their tank counterparts; they sacrificed speed for better protection.

One of the most successful German tank destroyers was the Sturmgeschütz III, a self propelled gun originally intended for infantry support with a design similar to the Jagdpanzer.

Soviet designs

As with the Germans, most of the Soviet designs mounted anti-tank guns, with limited traverse in casemate-style turretless hulls. The results were smaller, lighter, and simpler to build than tanks, but could carry larger guns. The Soviets produced the SU-85 and SU-100 self-propelled guns based on the same chassis as the T-34 medium tank, as well as the ISU-122 and 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 Elefants. The ISU-152 built as a heavy assault gun, relied on the weight of the shell fired from its M-1937/43 howitzer to defeat tanks.Forty and Livesey 2006 p. 329 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. The SU-76 "Suka" was originally designed as an anti-tank vehicle, but was soon relegated to the infantry-support role.Forty and Livesey 2006 p. 392

US designs

U.S. Army and counterpart 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; indeed, throughout the war only one battalion ever fought in an engagement quite like that which had originally been envisaged. The Tank Destroyer Command eventually numbered over 100,000 men and 80 battalions each equipped with 36 self-propelled tank destroyers or towed guns.

3in Gun Motor Carriage M10
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 gun in a limited-traverse mount, and called the 75-mm GMC M3. Another, considerably less successful, early design mounted a 37-mm anti-tank gun in the bed of a Dodge 3/4-ton truck - the 37-mm GMC M6. By far the most common US design was the 3in Gun Motor Carriage M10, later supplemented by the 90mm Gun Motor Carriage M36 and 76mm Gun Motor Carriage M18. The M18 came closest to the US ideal; the vehicle was very fast, small, and mounted a gun in a turret. The only dedicated American-origin, casemate hull design fighting vehicle of any type to be built during the war, that resembled the German and Soviet tank destroyers in hull and general gun mounting design, was the experimental T28 Super Heavy Tank, which mounted a 105mm T5E1 long-barrel cannon, which had a maximum firing range of 12 miles (20km), and was originally designed as a self-propelled assault gun to breach Germany's Siegfried Line defenses.

Of these tank destroyers, only the gun of the M36 proved to be effective against the Germans' larger armored vehicles at long range.Forty and Livesey 2006 p. 117 The open top and light armor made these tank destroyers vulnerable to anything greater than small-arms fire. As the number of German tanks encountered by American forces steadily decreased throughout the war, most battalions were split up and assigned to infantry units as supporting arms, fighting as assault guns or being used essentially as tanks.

British designs

Although initially flawed in its division of tanks into cruiser and infantry support roles, repeated encounters with German armor led the British to recognize the inevitability of tank-to-tank combat earlier than the Americans. As a result, there was extra impetus given to the development of anti-tank weaponry, which culminated in the Ordnance QF 17 pounder, widely considered one of the best anti-tank guns of the war.Forty and Livesey 2006 p. 116

Towed anti-tank guns were the domain of the Royal Artillery rather than the Royal Armoured Corps and vehicles adapted to mount artillery including anti-tank self-propelled guns such as the Deacon and Archer were their preserve.

Archer. The gun faced to the rear
The self-propelled guns that were built in the "tank destroyer" mold 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. 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 Tank Destroyer 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 was delayed until post war before entering service.

The closest the British came to developing an armored tank destroyer in the vein of the German Jagdpanzers or Soviet ISU series was the Churchill 3inch 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 Shermans in British use were being converted to Sherman Fireflies by adding the QF 17 pounder gun. Initially this gave each platoon of Shermans one powerfully-armed tank. By war's end, a higher proportion of Shermans were Fireflies.

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 gun. In the late 1960s, Germany developed the Kanonenjagdpanzer, essentially a modernized World War II Jagdpanzer mounting a gun. As Soviet designs became more heavily armored, the gun became ineffective and the Kanonenjagdpanzers were retrofitted for different roles or retired. Some provisions were made for the fitting of a 105mm cannon, and many of the vehicles were modified to fire HOT or TOW missiles in place of a main gun. These upgraded variants remained in service into the 1990s.

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 anti-tank 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 armored car and Sheridan light assault vehicle.

Modern tank destroyers

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

There have also been dedicated anti-tank vehicles built on ordinary armored personnel carrier or armored 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 anti-tank guided missile (ATGM) carriers instead of tank destroyers.

Some gun-armed tank destroyers continue to be used. The People's Republic of China has developed the tracked PTZ89 and the wheeled PTL02 tank destroyers. PTZ89 is armed with a smoothbore cannon while PTL02, developed by NORINCO for the PLA's new light (rapid reaction) mechanized infantry divisions, carries a one (a version armed with a 105mm rifled gun is available for export). PTL02 is built on the 6×6 wheeled chassis of the WZ551 APC.

Italy and Spain use the Italian-built Centauro, a wheeled tank destroyer with a 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 cannon which has remote control and autoloading capabilities. Originally, the Canadian Forces had considered replacing their aging Leopard 1 tanks with the Stryker Mobile Gun System. But with the increased use of IEDs capable of destroying Strykers by insurgent forces, they opted instead to purchase the Leopard 2 tank.

Source: Wikipedia