The submachine gun is an automatic or selective-fired shoulder weapon that fires pistol-caliber ammunition. The concept of submachine gun dates back to World War One; the trench warfare of this war required effective and compact weapons for short-range fighting in trenches; additionally, a lightweight and maneuverable fully automatic weapon was desirable to complement light machine guns in both defensive and offensive scenarios, to cover last 200 meters of assault on enemy positions.
The first weapon which can be considered to some extent as the world’s first submachine gun was the Italian Villar-Perosa, which was a twin-barreled automatic weapon that fired 9mm Glisenti pistol ammunition from top-mounted box magazines. It was compact, but its primary tactical role was of short-range machine gun; therefore it was usually fired from some sort of mount, and fitted with machine-gun type spade grips instead of more conventional rifle-type stock.
Submachine guns are lightweight automatic small-arms weapon chambered for relatively low-energy pistol cartridges and fired from the hip or shoulder. Most types utilize simple blowback actions. Using cartridges of such calibres as .45 inch or 9 mm, they usually have box-type magazines that hold from 10 to 50 cartridges, or occasionally drums holding more rounds. A short-range weapon, the submachine gun is rarely effective at more than 200 yards (180 m). It fires at rates as high as 650 or more rounds per minute and weighs 6 to 10 pounds (2.5 to 4.5 kg).