Tank destroyer
From Freepedia
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 for infantry or tank units, in defensive or withdrawal operations. They may mount a high-velocity anti-tank gun or sometimes an antitank guided missile launcher, or ATGM.
Tank destroyers cannot fulfil the many roles of tanks; they are much less flexible, and usually lack a strong anti-infantry capability. But they are much less expensive to manufacture, maintain, and resupply than tanks.
Gun-armed tank destroyers have been largely supplanted by the more general-purpose tanks since Second World War, but lightly-armoured ATGM carriers are used for supplementary long-range antitank capabilities.
World War II
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 a medium tank 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 a heavily-armoured vehicle that was more effective in armoured combat than enemy tanks.
German and Soviet designs mounted an antitank gun with limited traverse in a turretless hull. The result was smaller, lighter, and simpler to build than a tank, but could carry a larger gun. This was used by both forces to keep older designs competitive in the rapidly up-armoring of all AFV's that took place during the war.
For instance, the German Panzer I was obsolete before the war even started, with thin armor and only machine guns for armament. Yet they were forced into battle during the invasion of Poland, where they were found to be deathtraps. Before the invasion of France, 202 were rebuilt with a Czech 47 mm gun, becoming the Panzerjäger I. Soon the same sort of thing happened to the Panzer II during Operation Barbarossa: captured Soviet 76.2mm anti-tank guns were mounted on the Panzer II chassis, producing the Marder II. The most common mounting was a German 75 mm antitiank gun mounted on the ex-Czech Panzer 38(t) chassis to produce the Marder III. Whereas the Panzerjäger (German language: 'tank hunter') concept used the chassis of obsolescent tanks, dedicated Jagdpanzer (Ger. 'hunting tank') versions of tanks were developed later in the war. The Jagdpanther version of the Panther tank is considered the best of the Jagdpanzers. This vehicle mounted the L/71 version of the 88 mm gun on a reliable, highly mobile, well-armored chassis. The Soviets produced the 85 mm-armed SU-85 and 100 mm-armed SU-100 on the T-34 chassis, as well as the 122 mm-armed ISU-122 on the IS-2 heavy tank chassis.
The Germans became side-tracked into production of large numbers of tank-destroyers because they could be produced more cheaply than full tanks.
US Army tank destroyer doctrine
United States designs and British designs based on them were very different in conception. US doctrine was based on the need to defeat German blitzkrieg tactics. US units expected to be faced with large numbers of German tanks attacking on relatively narrow fronts. In actual practice, such attacks rarely happened. In pre-Second World War planning, US tanks were not intended to fight enemy tanks directly. Instead they were dedicated to the roles of infantry support and exploitation in a fast moving battle. In order to deal with the enemy tanks they would instead rely on tank destroyers, organized into separate units, dealing with armor at long range.
The resulting U.S. designs were intended to be very mobile and well armed, but with heavy firepower. Most retained the turret, but left it open on top both to save weight and to provide more working room for the larger gun. The earliest expedient design was an M3 half-track mounting an M1897 75 mm gun in a limited-traverse mount. The larger guns required a counterweight at rear of the turret, which can be seen on designs like the 3-inch gun M10 Wolverine and the 90 mm gun M36 Jackson. The M18 came closer to the US ideal; the vehicle was very fast, small, and mounted a 76 mm gun in a turret. The open top made them particularly vulnerable to artillery, air, and infantry assault, and the very idea of independent anti-tank groups was found unworkable.
By 1944, a number of the "basic" Shermans in British use were being converted to a Sherman Firefly by adding a 17 pounder gun - gaving each unit of Shermans a dedicated anti-tank tank. The 17 pounder was also mounted in the M10 Wolverine ("Achilles") and Archer tank destroyers in British service and two of their tanks; the Comet and the Challenger.
Virtually all US Infantry Divisions had a battalion of tank destroyers attached, and frequently a tank battalion also. In practice the two types of units were used interchangeably. In effect, the US Army had a mix of vehicles that were either under-armed (the tanks) or under-armored (the tank destroyers). Towards the end of the war, the arrival of the M26 Pershing medium tank showed that the lesson had been learnt.
Post–World War II development
With the development of flexible ATGMs which can be installed on almost any vehicle in the 1960s, the concept of the tank destroyer has waned. 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.
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 and Sheridan.
There have also been dedicated antitank vehicles built on ordinary armoured personnel carrier or armoured car chassis. Examples include the U.S. M901 "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 HS30 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.
