An Anti-Tank Guided Missile is a weapons system designed to defeat main battle tanks and other armored vehicles. ATGMs represent one branch of the on-going effort to defeat the tank. These weapons are are relatively light and inexpensive compared to other viable alternatives (say, another tank). They generally consist of a missile, launch tube which holds the missile until fired, and connects to it, a guidance system, and a wire (usually two for the sake of redundancy) to connect the missile and guidance system so the thing knows where to fly.

Tanks first appeared on the battlefield during the latter half of the First World War, and while their effect at the time was less than decisive, the tank's design and employment had barely begun, and most soldiers quickly realized that enemy tanks constituted a a grave threat to their own forces. All sides began a crash effort to develop effective counter-measures. The ideal anti-tank weapon would be lightweight and inexpensive enough to render the enemy tank essentially useless. Early anti-tank efforts concentrated on the gun, which was well-understood. A number of anti-tank rifles were produced and against the primitive WWI models the idea showed some promise. The-tank rifle persisted until World War II broke out and people actually tried hunting more modern tanks with them. After the war, surviving anti-tank rifles came to be known as elephant guns, as elephants proved inadequately armored against those heavy, single-shot rifles.

Tanks proved to be sterner stuff, and most anti-tank efforts focussed on using cannon. Early anti-tank guns were small cannon, with a bore small as 20mm. Germany began the war with a the 37mm PaK 36, France made a 25mm Hotchkiss and American infantrymen protected themselves with the 37mm M3. All proved useful against the lighter tanks used at the beginning of the war, but were soon rendered obsolete as newer tanks with thicker armor were introduced. German soldiers came to call the PaK 36 the "door knocker" because about the only thing it did to the Russian T-34 was let the Russian tankers know it was there and ready to be shot at. Still, these guns worked fairly well from an infantry point of view. The US M3 weighed just over 400 kilos (912 lbs) and was 13 feet long at full extension. It was small enough to be reasonably well-hidden, and could be manhandled by its crew into place. The later and more effective British six pounder (known as the M1 57mm in U.S. service) remained somewhat useful until the end of the war, and was small enough for people to handle.

Unfortunately for the gunners, tanks soon outgrew these weapons. The British Matilda infantry tank shocked the Germans as the only thing they had that would penetrate its sides was the 88mm Flak anti-aircraft gun. The T-34 repeated the German shock and led the Wehrmacht to begin developing pure anti-tank versions of the gun. All across the world, armies began turning anti-aircraft guns into anti-tank guns. The reasons were simple: while HEAT (shaped charge) warheads had appeared, the primary method of punching through armor combined a heavy shell with high velocity. Heavy anti-aircraft guns were expected to throw a shell capable of killing with a near miss six (or more) miles into the sky. Thus the German 88 had both the shell-weight and muzzle velocity to kill even heavy tanks, and was later mounted on the German Tigers. The Brits adapted their 17 pounder. The American M1918 3" anti-aircraft gun was morphed into the M5 76.2mm and fitted to the M10 tank destroyer and later models of the Sherman tank. The 90mm M8 proved even more effective and was turned into a towed weapon and fitted onto the M36 Jackson tank destroyer and the M26 Pershing tank.

These newer, heavier guns, while effective, really didn't do the poor bloody infantry much good. The towed version of the 76mm M5 weighed over 2 tons (metric) and was almost 10 meters long with the gun in firing position. Manhandle it into place? In your dreams! And not very quickly either. Worse, the M5 didn't do very well against a Panther or Tiger unless you had the rare HVAP ammunition or the enemy tank was entirely too close. Soldiers moved the gun into position with aid of a prime mover, usually a half-track. It took a long time to emplace, almost as long to disemplace and provided absolutely zero protection for the crew against various types of enemy fire. Casualties among gunners proved very high. On a mobile battlefield, the guns were too easily bypassed, and often proved useless.

So they decided to mount the big gun on a vehicle. As the guns were getting pretty big, the best chassis was shared with a tank. Examples include the German Jagdpanther assault gun or US M10 and M36 tank destroyers. These specialized anti-tank vehicles cost somewhat less than the equivalent tank but the disadvantages (limited traverse on the Jagdpanther, inadequate armor for most tank destroyers) led to an epiphany: the best and most cost-effective way to bring an anti-tank gun to fight was to put it into another tank! And so tanks are considered to be the best anti-tank vehicles to this day.

Of course the gun was not the only approach tried. Shaped charge warheads offered the possibility of killing armored vehicles with a lightweight, inexpensive warhead. Shaped charge (or HEAT for High Explosive Anti-Tank) warheads are as effective at long range as close in. The American bazooka and the German Panzerfaust were the best known weapons of this type. Basically you mounted a shaped charge warhead on top of a rocket and fired the rocket at the tank. The panzerfaust in particular proved quite effective, enough so that the Russians copied it as the RPG-2 then upgraded it into one of the Third World's favorite weapons, the nigh-ubiquitous RPG-7. Unfortunately these weapons also had their limitations. To kill a tank with a shaped charge you need to hit it pretty square, or most of the blast will slide by the armor. And neither the bazooka or the RPGs are terribly accurate weapons. To hit with confidence you had to let the tank get really close. Close enough that an alert tank crew will very likely have killed a lot of defending infantrymen before you get your shot. Closer then you can likely get if the tank is supported by infantry. Gunners who miss enjoy short, interesting lives. Better to keep the big armored things far, far away.

Thus was born the ATGM. If the rocket isn't very accurate just add a guidance system to make it hit. The concept had been proven in combat with the German FritzX anti-shipping missile, which was used to sink the Italian flagship, the battleship Roma. The transistor made possible electronics compact and light enough to pack in an effective guidance system. The first to build one effectively were the French. German tank tactics had left a bitter memory in the mind of French soldier and with the Russians building thousands of tanks and Germany re-arming to join NATO the French wanted an equalizer. So they created the SS.11 in 1953. It was wire guided and employed Manual Command Line to Line Of Sight (MCLOS) guidance. Using an SS-11 (or the Russian AT-3 Sagger) was sort of like playing Galaxian. Keep your eye on the target and use a joystick to steer the missile. The signal was carried through wires left behind during the missile's flight.

While effective for the time (just ask Israeli tankers who faced the Saggers during the 1973 Yom Kippur War) the early systems required a lot of skill and missed a lot. The 2nd Generation included the US TOW and the European Milan anti-tank missile. All the operator had to do was keep his eye on the target and the guidance system will do the rest. But did they do in the tank? Nope. Wires can be, and often are, cut during heavy combat when the hot metal is flying. Most missiles don't fly very fast, as high speed would have made the missiles a lot bigger and heavier, and thus less portable even if they really aren't light enough to be called man-portable. Tank shells and bullets fly supersonic. Also most of the weapons must be blown out of their launch tube by a small charge before it takes flight. Often the result is a quite noticeable back blast. Experienced tankers know to look for the back blast, then shoot back and take other measures to ensure their survival. The relative speeds of the ordinance means the tank's response may hit before the missile. Tank shells hit hard enough to disturb even a brave man's aim. Of course not all tank crews are so alert, well trained, or lucky. Operators can be well dug in or kept under armor to improve their confidence and keep their eye on the target.

The Wire in ATGMs is starting to be phased out in favor a beam (radio, laser etc) which are less vulnerable to shrapnel, tangling and other issues. The Javelin is one of a new generation of fire-and-forget self-guiding missiles which don't have the vulnerabilities of earlier generation operator-controlled missiles. They have new vulnerabilities though it may take some time before they are sorted out. The struggle goes on. The ATGM is far from dead on the world's battlefields. They remain capable of killing tanks, armored vehicles and heavy fortifications and that's reason enough to justify their existence.

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