launcher is a type of unguided rocket artillery system. Like other rocket artillery, multiple rocket launchers are less accurate and have a much lower (sustained) rate of fire than batteries of traditional artillery guns. However, they have the capability of simultaneously dropping many hundreds of kilograms of explosive, with devastating effect. The Korean Hwacha is an example of an early weapon system with a resemblance to the modern-day multiple rocket launcher. The first self-propelled multiple rocket launchers – and arguably the most famous – were the Soviet BM-13 Katyushas, first used during World War II and exported to Soviet allies afterwards. They were simple systems in which a rack of launch rails was mounted on the back of a truck. This set the template for modern multiple rocket launchers. The first modern multiple rocket launcher was the German 15 cm Nebelwerfer 41 of the 1930s, a small towed artillery piece. Only later in World War II did the British deploy similar weapons in the form of the Land Mattress.The Americans mounted tubular launchers atop M4 Sherman tanks to create the T34 Calliope rocket launching tank, only used in small numbers, as their closest equivalent to the Katyusha. Missile vehicle Missile vehicles are trucks or tractor units designed to carry rockets or missiles. The missile vehicle may be a self-propelled unit or the missile holder/launcher may be on a trailer towed by a prime mover. They are used in the military forces of a number of countries in the world. Long missiles are commonly transported parallel to the ground on these vehicles, but elevated into an inclined or vertical position for launching. A Transporter erector launcher (TEL) is a missile vehicle with an integrated prime mover (tractor unit) that can carry, elevate to firing position and launch one or more missiles. Such vehicles exist for both surface-to-air missiles and surface-to-surface missiles. Tank destroyer Tank destroyers and tank hunters are armed with an anti-tank gun or anti tank missile launcher, and are designed specifically to engage enemy armoured vehicles. Many have been based on a tracked tank chassis, while others are wheeled. Since World War II, main battle tanks have largely replaced gun-armed tank destroyers; although lightly armoured anti tank guided missile (ATGM) carriers are commonly used for supplementary long-range anti-tank engagements. In post-Cold War conflict, the resurgence of expeditionary warfare has seen the emergence of gun-armed wheeled vehicles, sometimes called "protected