The Villar Perosa is one of the first small machine guns developed and used by a military force. It was designed in Italy and introduced in 1915 as an aircraft weapon, to be used in a flexible mount by an airplane's observer. The gun consists of two independent firing actions mounted together. Each fires from an open bolt as a rate of 1200-1500 rounds/minute, feeding from a 25 round magazine of 9mm Glisenti cartridges. This allowed the maximum possible volume of fire in an aerial combat situation, where in 1915 ballistic power was not particularly important.
As aircraft armaments improved and synchronized, belt-fed machine guns became practical, the Villar Perosa was quickly made obsolete in aerial use. The Italian military experimented with several applications of the weapon in ground combat, including slings and belt fittings for marching fire, tripods, mounts with integral armor shields, and bicycle mounts. None of these proved particularly successful, as the elements that made the gun well adapted to early aerial use (high rate of fire with a small cartridge) made it relatively ineffective for infantry use.
Ultimately, the best use of the Villar Perosa was to break them up and convert the actions into shoulder-fired submachine guns. Designs to do this were developed by both the Beretta company and Villar Perosa themselves, and in 1918 these guns entered service at the same approximate period as the first German MP-18 submachine guns. Because of this recycling, intact M1915 Villar Perosa guns are quite rare today.