Online Encyclopedia
Anti-tank
Anti-tank, or simply AT, refers to any method of combating military armored fighting vehicles, notably tanks. The most common forms of anti-tank systems are cannons with a high muzzle velocity, wire guided missiles in various forms, and various autocannon firing penetrating ammunition.
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Early systems
Small cannon and large-calibre rifles were used against the early WWI tanks being introduced by the British Expeditionary Force (BEF), many of which proved to be almost useless. By the end of the war a number of light guns, typically 37 mm (2-pounder in British measure) were being deployed on short carriages that proved to be considerably better. In addition most forces deployed large high-velocity rifles, typically of 50-cal (12.7 mm) calibre, with enough power to puncture the thin armor of the tanks of the era.
Anti-tank guns
Anti-tank guns are guns designed to destroy armored vehicles. In order to penetrate the armor of tanks and other armored vehicles they fire high-velocity shells.
Prior to World War II anti-tank guns were relatively small, with anti-tank rifles primarily used for destroying tanks. Few had barrel diameters larger than 50mm. With the rapid improvement in tank armor and guns anti-tank guns increased in barrel size, firing larger shells at greater velocities. One of the most noteworthy of these weapons was the German 88mm gun, which was orginally developed as an anti-aircraft but found widespread use in destroying tanks. Likewise, by the end of the war all sides were using guns with diameters of 90mm and up.
World War II also saw the mounting of antitank guns on vehicle chasises, sometimes armored, as a cheap substitute for a full-fledged tank. Some had open turrets, while others did not have rotating turrets at all, meaning that the whole vehicle had to be rotated to aim the gun. Americans called these vehicles tank destroyers.
At the start of World War II many of these weapons were still being used operationally, along with a newer generation of light guns that little changed from their WWI counterparts. In combat both proved entirely useless against the larger and better armored tanks they faced. For instance, the German army had recently introduced a new lightweight 37mm gun, whose users quickly nicknamed it the "armored door knocker" because all it seemed to do was announce its presence.
All combatants quickly introduced newer and more powerful guns, and the anti-tank rifle had largely disappeared by 1942. The "average" gun by 1943 was 50mm or larger, the Germans had an excellent 50mm high velocity design, while the British introduced the "6-pounder" which was also adopted by the US Army as the 57mm. A year later sizes had grown due to pressure on the Eastern Front, German guns were now 75mm and the famous 88mm, while their Soviet counterparts were mounting a variety of 100mm and 122mm guns.
As the guns grew in size they dropped in mobility, leading to the development of the anti-tank vehicle, typically a tank chassis with a much larger gun mounted on top. By the end of the war the concept of the dedicated anti-tank gun was essentially dead, the guns were so large that they were essentially immobile.
HEAT
A parallel evolution was taking place at this time however, anti-tank weapons based on HEAT warheads using a Munroe effect shaped charge. These self-forging explosive munitions could penetrate even more armor than some of the largest anti-tank guns, yet weighed only a few pounds. Typically delivered by a small rocket fired at short range, HEAT formed the basis of the British PIAT, US Bazooka and German Panzerfaust, Panzerschreck and the recoilless rifle. In many cases these weapons were so effective that the concepts of Blitzkrieg could often be stopped cold by properly equipped troops.
The Germans even used HEAT warheads on their now useless 37mm guns to deliver the warheads at ranges that the rockets couldn't match. However the effectiveness of a HEAT warhead is strongly related to its diameter, so while HEAT was not too effective on "larger" guns like the 75 and 88, on the 37 this was solved by placing an oversized warhead on the outside of the barrel, popped off in a manner similar to a rifle grenade. This ad-hoc solution was used only in desperation, the recoilless rifle offered the same performance from a much lighter breech-loading gun.
Post-war developments
In the post-WW II era HEAT became almost universal. The British developed the HESH, or high explosive squash head, as an anti-concrete device for attacking fortifications, and found it surprisingly effective against tanks. In general these systems allowed infantry to take on even the largest tanks, albeit at short ranges. But the short range of the delivery systems remained a problem. Increasing use of combined arms tactics allowed the attacking infantry to suppress the anti-tank crews effectively, meaning that they could typically get off only one or two shots before being countered or forced to move.
The search for a suitable longer-range delivery system took up much of the immediate post-war era. The US invested in the recoilless rifle, delivering a widely used 75mm design, and less-common 90mm and 106mm designs (this last one was usually mounted on a jeep rather than hauled across the battlefield by infantrymen). The 106mm formed the basis of a dedicated anti-tank vehicle, the Ontos tank, which mounted six. The Russians also built recoilless rifles in various calibers intended to be used as antitank weapons, most commonly 73mm, 82mm, and 110mm (only the 73mm remains in service with the Russian military today, though the other two can be found all over the world, courtesy of Soviet military aid during the Cold War). A massive 120mm (4.7-inch) recoilless rifle was built in the UK and issued briefly, but it was found to be too heavy and too massive to be useful, as it had to be deployed mounted on the back of a truck. However most forces, the US included, invested heavily in the development of the wire guided missile as a delivery system, eventually delivering systems in the 1960s that could defeat any known tank at ranges outside that of the guns of the accompanying infantry. The United Kingdom, France, and other NATO countries were among the first to develop such weapons (e.g. the Malkara missile). The United States was one of the last, coming up with the BGM-71 TOW, which was more powerful and easier to use than all the previous missiles, and eventually came to be the most widespread wire guided anti-tank weapon in the West.
Of the world's major armies, only the Russians, and of course their allies, retained the antitank gun in significant quantities, mostly in calibers 100mm, 115mm, and, currently in Russia, 125mm. The 125mm antitank guns are extremely bulky and massive, and require large tractors to tow them for any significant-distance cross-country, but they're cheap, deadly (particularly now that they've been upgraded with laser rangefinders and depleted uranium ammunition), and as tactically useful as they ever were.
For a time it appeared that the tank was a dead end, a small team of infantry with a few missiles in a well hidden spot could take on a number of the largest and most expensive tanks. In the 1973 Yom Kippur War, Soviet first-generation wire guided missiles being fired by the Egyptian forces inflicted heavy casualties on IDF tank units, a battle that caused a major crisis of confidence for tank designers.
Rebirth of the tank
As bad as it looked for the tank in the 1960s, increases in depth of armor and improvements in armor technology meant that hand-held systems were no longer large enough to deliver enough power by the 1970s, and the introduction of Chobham armour by the UK and reactive armor by the USSR, forced the HEAT rounds to be so large that in many cases they are no longer truly man-portable.
Today the anti-tank role is filled with a variety of weapons, from portable "top attack" missiles, to larger HEAT based missiles for use from jeeps and helicopters, a variety of high velocity autocannon, and ever-larger heavy tank guns.