
However, the war ended before prototypes could be shipped to Europe. 45 ACP Thompson submachine gun had been in development at approximately the same time as the Bergmann and the Beretta. Thompson M1921 SMG with 100-round drum magazine In addition, some compact assault rifles, such as the Colt XM177 and HK53, have been historically referred to as submachine guns as they served in the latter's role. Also, Personal Defense Weapons such as the FN P90 and H&K MP7 are often called submachine guns. However, the term " machine pistol" is also used to describe a handgun-style firearm capable of fully automatic or burst fire, such as the Stechkin, Beretta 93R and the H&K VP70. Other sources refer to SMGs as "machine pistols" because they fire pistol-caliber ammunition, for example, the MP-40 and MP5, where "MP" stands for Maschinenpistole ("Submachine gun" in German, but cognate with the English term "Machine pistol"). British Commonwealth sources often refer to SMGs as "machine carbines". There are some inconsistencies in the classification of submachine guns.

The submachine gun was developed during World War I (1914–1918) as a close quarter offensive weapon, mainly for trench raiding.

As a machine gun must fire rifle cartridges to be classified as such, submachine guns are not considered machine guns. Thompson, the inventor of the Thompson submachine gun, to describe its design concept as an automatic firearm with notably less firepower than a machine gun (hence the prefix " sub-").

The term "submachine gun" was coined by John T. Thompson holding a Thompson M1921Ī submachine gun, abbreviated SMG, is a magazine-fed, automatic carbine designed to fire handgun cartridges.
