although it never saw use in combat. The Germans also experimented with machine pistols by converting pistols such as the Mauser C96 and Luger P-08 from semi-automatic to fully automatic operation and adding detachable stocks. Carbine-type automatic weapons firing pistol rounds were developed during the latter stages of World War I by Italy, Germany and the United States. Their improved firepower (800-1000RPM) and portability offered an advantage in trench warfare, where most troops were issued bolt-action rifles, such as the Gewehr 98 or Lee–Enfield. In 1915, the Kingdom of Italy introduced the Villar-Perosa aircraft machine gun. It fired pistol-caliber 9mm Glisenti ammunition, but was not a true submachine gun, as it was originally designed as a mounted weapon. This odd design was then modified into the OVP 1918 carbine-type submachine gun, which then evolved into the 9×19mm Parabellum Beretta Model 1918 after the end of World War I. Both the OVP 1918 and the Beretta 1918 had a traditional wooden stock, a 25-round top-fed box magazine, and had a cyclic rate of fire of 900 rounds per minute. The Germans initially used heavier versions of the P08 pistol equipped with a detachable stock, larger-capacity snail-drum magazine and a longer barrel. By 1918, Bergmann Waffenfabrik had developed the 9 mm Parabellum MP 18, the first practical submachine gun. This weapon used the same 32-round snail-drum magazine as the Luger P-08. The MP 18 was used in significant numbers by German stormtroopers employing infiltration tactics, achieving some notable successes in the final year of the war. However, these were not enough to prevent Germany's collapse in November 1918. After World War I, the MP 18 evolved into the MP28/II SMG, which incorporated a simple 32-round box magazine, selective fire, and other minor improvements. Though the MP18 had a rather short service life, it was influential in the design of later submachine guns, such as the Lanchester, Sten and PPD-40. The .45 ACP Thompson submachine gun had been in development at approximately the same time as the Bergmann and the Beretta. However, the war ended before prototypes could be shipped to Europe. Although it had missed its chance to be the first purpose-designed submachine gun to enter service, it became the basis for later weapons, and was much more successful than the other submachine guns produced during World War I. Interwar Period In the interwar period, the Thompson, nicknamed "Tommy Gun" or "Chicago