Anti-tank warfare arose as a result of the need to develop technology and tactics to destroy tanks since the introduction of tanks during the First World War.
In R.U.S.E., anti-tank units excel at destroying armored vehicles at long range. Be careful though that anti-tank units are unable fire at infantry and aircraft so they can be easily destroyed by infantry ambushes and air raids. Anti-tank units can be classified into three groups: mobile, guns, and fortifications.
Mobile anti-tanks (tank destroyers) are mobile units that typically have heavy firepower but at the expense of light armor. A recurring factor in tank destroyer is that they don't have turrets (excluding the Wolverine, Jackson and Firefly). Unlike static anti-tank guns they don't need time to set up and can keep up with your tanks off road, and are thus can take on an offensive role.
Anti-tank guns are towed units which are slow and must set-up prior to firing. Unlike tank destroyers, anti-tank guns do not much offensive capability, and are more suited to defense. These units are best placed in forests where they can ambush enemy tanks from afar. A common tactic with anti-tank guns is to set up an ambush by luring an enemy armored column into the sights of guns, which remain hidden in a forest.
Certain defensive fortifications are equipped with anti-tank guns. Like anti-tank guns, anti-tank equipped bunkers are suited for defense rather than offense, as they cannot move at all. They are useful at defending choke-points and bases, but are very vulnerable to aircraft, even fighter-bombers, and must be paired with a strong anti-aircraft defense.