The invention of a compact, highly mobile military firearm that could produce rapid, repeating fire to repel an attacking force or act as an offensive or defensive force multiplier had been sought for nearly 900 years. Early attempts to invent a repeating, fully automatic weapon resulted in bulky and semi-reliable guns consisting of single shot barrels gathered together and hand-held as a pistol or as a rifle. They took a considerable time to reload and could be as deadly to the user as to an attacking enemy. These "small arms" evolved into semi-automatic weapons, and fully automatic submachine guns, machine pistols and assault rifles.

Multi-shot small arms came into military use beginning in the mid-1600's. They included the Kalthoff repeater, the Nock Volley Gun, various "pepperbox" pistols, the "duck foot" pistol, derringers, double-barreled pistols, rifles and shotguns, and other weapons of various designs.

Initial development of automatic small arms came from European inventors in Italy, Austria-Hungary and Germany. These resulted in fully automatic versions of semi-automatic pistols such as the Austro-Hungarian Steyr M1912/P16, the German Mauser C96, and an artillery version of the Luger P-08 (using a longer and heavier barrel than a normal Luger), each with a detachable shoulder stock. The first practical submachine gun was also developed in Germany in 1918, as the Bergman MP18. It utilized the same 32-round snail drum developed for the Luger P-08. The Bergman was later developed into the MP28/II which was fed by a side-mounted 32-round box magazine. The Bergman weapons influenced the development of later German and other nations' submachine guns, such as the British Lanchester, Sten and Sterling, the Soviet PPSh-41, the Finnish Suomi KP/31, the Italian Beretta Model 38, and the Japanese Type 100.

Other firearms innovators, including John T. Thompson (1860-1940), produced such well-known guns as the M1921 Thompson submachine gun, the famous "tommy gun." Thompson designed it as a mobile, light machine gun for use by soldiers on the attack as a "trench broom" or "trench sweeper" during World War I. The Thompson submachine gun saw service throughout the 20th Century and many serve still well into the 21st Century. A cheaper submachine gun, which saw continued use well into the Vietnam War was the M3 Grease Gun. It was used as a personal defense weapon by tank and vehicle crew members. Germany continued submachine gun development with its MP series, the MP-36, MP-38, MP-40 and MP-41. The MP-38 and MP-40 were the best known of these and are the ubiquitous submachine gun designs associated with WWII German soldiers. Other examples such as the Australian Owen Gun and the American Reising submachine gun are lesser-known designs that were used in the Pacific Theater.

Germany developed several arms that branched off from the submachine gun as assault or battle rifles in the Hugo Schmeisser (1884-1953)-designed Sturmgewehr (storm rifle) 44, and a similar Mauser design, the StG-45. The StG's and a contemporary Soviet design, the AK-47, changed the fundamental idea of the kind of weapon an individual soldier carried into battle.

The technological advances made during World War II and the advent of the Cold War (1947-1991) influenced further refinements throughout the world. The submachine gun was largely replaced worldwide militarily by the modern assault rifle. The best known of these were Mikhail Kalashnikov's (1919-2013) AK-47 assault rifle and its derivatives and copies, and the American M16 and its derivatives. Also, various other designs such as the Belgian FN FAL (Fabrique Nationale Fusil Automatique Leger) and the German HK G3 (Heckler and Koch) came into common use. Submachine guns continued to be used in specialized and supplemental roles. Best known of these were the Israeli Uzi, the German HK MP5, the Swedish K, the French MAT-49, the Italian Beretta M12S, and the Ingram MAC 10.

This guide does not include materials on the topics of gun control, assault weapon bans, or mass casualty shootings.