A machine gun is a fully-automatic weapon using a caliber equal or smaller than 15 mm. Firearms using a greater caliber are called autocannons. The strength of this kind of weapon is the fire power delivered by the high rate of fire, and the fact that they can be carried.

The idea of creating a weapon able to fire projectiles with a high rate of fire is not recent. Since the 14th century Leonard De Vinci drew a similar weapon, but the plan never came true. The first firearms created that was similar to machine guns appeared during the 18th and 19th century but their interest were reduced because of their lack of mobility.

The firsts effective machine guns appeared during the second half of the 19th century, indeed, Richard Gatling, an American inventor, created the first machine gun in 1861. Its design main features were the presence of then barrels, and a hand-operated crank. In the 1880's Hiran Maxim, another American inventor, created the first truly automatic machine gun. Then, numerous European countries, such as England or Germany bought copies of this firearm. At this moment, the machine guns showed how effective they could be, notably during the colonial battles, like the one that took place in South Africa in 1893, when 50 soldiers and four Maxim guns defeated 5000 Matabele warriors.

Nowadays, there are many types of machine guns, such as heavy or light machine guns. Besides, machine guns are no longer only reserved to infantry, but are now used on military vehicles such as aircrafts, tanks, or helicopters.