A tank destroyer, tank hunter, tank killer, or self-propelled anti-tank gun is a type of armoured fighting vehicle, armed with a direct fire artillery gun or missile launcher, designed specifically to engage and destroy enemy tanks, often with limited operational capacities. While tanks are designed for front-line combat, combining operational mobility and tactical offensive and defensive capabilities and performing all primary tasks of the armoured troops, the tank destroyer is specifically designed to take on enemy tanks and other armoured fighting vehicles. Many are based on a tracked tank chassis, while others are wheeled. Since World War II, gun-armed powerful tank destroyers have fallen out of favor as armies have favored multirole main battle tanks. However, lightly armoured anti-tank guided missile (ATGM) carriers are commonly used for supplementary long-range anti-tank work. The resurgence of expeditionary warfare in the first two decades of the 21st century has seen the emergence of gun-armed wheeled vehicles, sometimes called "protected gun systems", which may bear a superficial resemblance to tank destroyers, but are employed as direct fire support units typically providing support in low-intensity operations such as the wars in Iraq and Afghanistan. World War II Dedicated anti-tank vehicles made their first major appearance in the Second World War as combatants developed effective armoured vehicles and tactics. Some were little more than stopgap solutions, mounting an anti-tank gun on a tracked vehicle to give mobility, while others were more sophisticated designs. An example of the development of tank destroyer technology throughout the war are the Marder III and Jagdpanzer 38 vehicle, that were very different in spite of being based on the same chassis: Marder was straightforwardly an anti-tank gun on tracks whereas the Jagdpanzer 38 traded some firepower (its 7.5 cm Pak 39, designed to operate within the confines of a fully armoured fighting compartment, fires the same projectiles from a reduced propellant charge compared to Marder's 7.5 cm Pak 40) for better armour protection and ease of concealment on the battlefield. Except for most American designs, all tank destroyers were turretless vehicles with fixed or casemate superstructures. When a tank destroyer was used against enemy tanks from a defensive position such as by ambush, the lack of a rotating turret was not particularly critical, while the lower silhouette was highly desirable. The turretless design allowed accommodation of a more powerful gun, typically a dedicated anti-tank gun (in lieu of a regular tank's