Katyusha multiple rocket launchers (Russian: Катюша) are a type of rocket artillery originally built and fielded by the Soviet Union in the Second World War. Compared to other types of artillery, such multiple rocket launchers are able to deliver a devastating amount of explosives to an area target more quickly but with lower accuracy and requiring a longer time to reload. These vehicles are fragile compared to conventional artillery guns, but relatively inexpensive and easy to produce. Katyushas of World War II, the first self-propelled artillery mass-produced by the Soviet Union, were usually mounted on trucks. This mobility gives Katyushas (and other self-propelled artillery) another advantage: they are able to deliver a blow all at once, and then move before the other side is able to locate their position and attack it with counter-battery fire. Katyusha weapons of World War II included the BM-13 launcher, light BM-8, and heavy BM-31. Today, the nickname is also applied to newer truck-mounted Soviet multiple rocket launchers—notably the very common BM-21—and their derivatives worldwide. (via Wikipedia)