MLRS (Multiple Launch Rocket System) is a tracked or wheeled vehicle mounting a rocket launching (projecting) system atop its hull. In this configuration, the MLRS projects unguided rockets against enemy positions in an artillery-minded sense. The MLRS offers a devastating physical and psychological effect on the enemy, capped with high explosive, anti--personnel or chemical warheads as needed. The best known MLRS development is the timeless BM-13 "Katyusha" wheeled system of the Soviet Union used during World War 2, seeing widespread exportation to its allies in the years following. The Western modern equivalent is the American M270 MLRS. Systems on order heading into 2015 are NOT taken into account. MLRS strength data through 2014.
Sources: CIA.gov, CIA World Factbook, wikipedia.com, public domain print and media sources and user contributions. Some values may be estimated when official sources are lacking.