A multiple rocket launcher (MRL) is a type of unguided rocket artillery system. Like other rocket artillery, MRLs are less accurate and have a much lower 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.
One of the first modern multiple rocket launchers was the German Nebelwerfer of the 1930s, a small towed artillery piece. Only later in World War II did the Allies deploy similar weapons in the form of the Land Mattress.
The first self-propelled multiple rocket launchers — and arguably the most famous — were the Soviet Katyushas, known also as Stalin's organs, 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.
Further developments followed the same design pattern, although larger systems with more sophisticated projectiles are seen. The Russian BM-30 Smerch MLRS (Multiple Launch Rocket System) is one example of a modern system, in service with several countries, the U.S. M270 and Russian TOS-1 Buratino are others . Many modern multiple rocket launchers have regular, extended-range, and guided ammunition available with antipersonnel, cluster, antitank, incendiary, and biological or chemical warheads.