The machine gun directly impacted the organization of the infantry in 1914, and, by the middle of 1917, put an end to the tactic of company sized waves. Platoons and squads of men became important; hand in hand with that organization was the use of light automatic weapons.

The Lewis Gun was the first true light machine gun that could in theory be operated by one man, though in practice the bulky ammo pans required an entire section of men to keep the gun operating.

The Browning Automatic Rifle was adopted by the U.S. Army in 1918; adapters on cartridge belts allowed the BAR man to walk and fire the gun at the same time. Early sub-machine guns were also developed in this period. While in use, these guns would often overheat - which led to the development of several cooling methods.

There were many innovations in weaponry during World War One. The machine gun received the most credit because of the damage it did in the trenches and its overall devastation.