Tanks are armored vehicles which use heavy-duty tracks for mobility. There are many types of tank armor that have been employed since the first tanks were manufactured during World War I. Since tanks are most often pointed toward the direction of enemy fire, the heaviest armor is in the front. Ideally, tank armor will be able to protect the tank and its crew from a wide variety of possible threats.
The first tank prototype was tested for use by the British army on 8 September 1915. The French and German armies also later developed tanks, and these developments helped change the way the war was fought, and make trench warfare essentially obsolete. Steel plating was the earliest type of tank armor that was commonly used. The development of more deadly forms of weaponry in World War II necessitated new developments in armor technology.
Composite armor was a major development by the British, who made this innovation by mixing ceramics and plastics in resin, and placing it between two steel plates. This type of tank armor provides good protection against many types of more advanced weaponry, including high explosive anti-tank (HEAT) shells. Later on, other materials such as depleted uranium came to be added to composite armor.
Physical armor can only do so much, however, and as weapons have advanced further, the emphasis has come to be placed on what are known as active protection systems. These systems protect a tank from weapons before they ever hit the tank armor. These systems can focus on confusing the guidance system of an incoming missile, or on simply knocking it out of the air and destroying it from a safe distance.
Developments in tank armor can be described by grouping them together into several categories. One of the simplest is called appliqué armor, which often consists of metal plates welded onto the existing armor. They are designed to protect against weapons that would penetrate the original armor of the tank.
Spaced armor is very commonly used, and has been since World War I. Spaced tank armor consists of two or more plates that are a certain distance apart. In some cases, this protects against ammunition that disintegrates progressively after penetrating each plate. It is most effective against HEAT shells, because these are very effective at the point where they hit, but not far beyond that.
Reactive armor is one of the more interesting developments. This consists of armor that actually explodes itself in an attempt to deflect warheads. Friendly troops near this type of armor can unfortunately be in danger when it detonates. However, there is also non-explosive reactive armor, which employs materials that change their geometry at the moment of impact to provide extra protection under stress.
