Basically, the grenade launcher is a weapon which fires a grenade â€“ a small shell, filled with high explosive or other agent, such as tear gas for less lethal application, bright burning compound for illumination purposes, incendiary filling etc. Of course, in most cases the grenade also must be fitted with a fuse, and with a safety, to avoid damage to the grenadier or handler. The simplest way to use the grenade is to throw it by hand; but the effective range and maximum weight of hand grenades is severely limited; so, at the earliest stages of the development of firearms, many armies used so called â€œhand mortarsâ€ â€“ basically, the smoothbore muskets with short barrel of very large caliber, which was used to fire standard grenades at ranges beyond the limits of human throwing ability. During the First World War most nations started to use so called â€œrifle grenade launchersâ€. These launchers in fact were add-ons to standard issue military rifles, usually in the shape of a cup, attached to the muzzle of the rifle. A grenade was placed into this cup, primed, the rifle aimed toward the enemy, and then the grenade was launched using a special blank cartridge. he actual choice of the type of grenade launcher varies â€“ some countries, most notably the USA and the former USSR/Russia, stuck completely with underbarrel grenade launchers, some others, like Belgium or France, seemed to prefer rifle launcher type, while many other countries, such as Germany, produced both types of weapon,. The post-war period saw a short period of renaissance of the stand-alone grenade launchers, similar in basic idea to the â€œhand mortarsâ€ mentioned above. First these were re-introduced in service by the Germans during WW2, as the â€œkampfpistoleâ€ â€“ a modified flare launcher, fitted with a rifled barrel and a detachable shoulder stock, and firing various types of grenades. In the postwar period, several countries developed single-shot, shoulder-fired grenade launchers, usually of 40mm caliber, which actually preceded the modern underbarrel grenade launchers and used the same types of ammunition. The most famous of these is probably the US M79 â€œthumperâ€, widely used during the Vietnam War. The key problem with these weapons was that they required the grenadier to carry some sort of personal defense firearm in addition to the grenade launcher, such as a pistol, submachine gun or rifle. Latter on, several countries produced multi-shot versions of stand-alone shoulder fired grenade launchers, usually in the form of a large revolver, or a pump-operated rifle with a tubular magazine. Military users mostly replaced these weapons with underbarrel grenade launchers, and stand-alone launchers are mostly used either by special operations forces or by police forces, which employ the launchers for less-lethal anti-riot applications, firing tear gas canisters and baton rounds (rubber projectiles or buckshot).