7.92×33mm Kurz in the context of Sturmgewehr 44

An assault rifle is a select fire rifle that uses an intermediate-rifle cartridge and a detachable magazine. Assault rifles were first put into mass production and accepted into widespread service during World War II. The first assault rifle to see major usage was the German StG 44, a development of the earlier Mkb 42. While immediately after World War II, NATO countries were equipped with battle rifles, the development of the M16 rifle during the Vietnam War prompted the adoption of assault rifles by the rest of NATO. By the end of the 20th century, assault rifles had become the standard weapon in most of the world's armies, replacing full-powered rifles and submachine guns in most roles. The two most successful modern assault rifles are the AK-47 and the M16 designs and their derivatives.

A fully powered cartridge, also called full-power cartridge or full-size cartridge, is an umbrella term describing any rifle cartridge that emphasizes ballistics performance and single-shot accuracy, with little or no concern to its weight or recoil. The term generally refers to traditional cartridges used in machine guns, bolt action and semi-automatic service rifles and select fire battle rifles prior to, during and immediately after the World Wars and into the early Cold War era, and was a retronym originally made to differentiate from intermediate-power rifle cartridges that gained widespread adoption into military service after World War II.

Full-power cartridges often have a caliber comparable to or greater than 7.5 mm (0.30 in) and a maximum effective range of at least 800 m (870 yd), and are intended for engaging targets beyond 300 m (330 yd). However, cartridges with calibers as narrow as 6.5 mm (0.26 in) have been described as being a full-power rifle cartridge. According the cartridge's overall length (COL), full-power cartridges can be grouped into long-action or "standard-action" cartridges, which are traditional cartridges (exemplified by the .30-06 Springfield, 8mm Mauser and 7.62×54mmR) with a COL between 72 and 85 mm (2.8 and 3.3 in); and short-action cartridges (such as the .308 Winchester and 6.5mm Creedmoor), which have a COL between 57 and 72 mm (2.2 and 2.8 in) and largely replaced long-action cartridges as battle rifle service ammunitions since the Cold War. Cartridges with a COL above 85mm are often however considered magnum cartridges instead of "full-powered".

An intermediate cartridge is a rifle/carbine cartridge that has significantly greater power than a pistol cartridge but still has a reduced muzzle energy compared to fully powered cartridges (such as the .303 British, 7.62×54mmR, 7.65×53mm Mauser, 7.92×57mm Mauser, 7.7×58mm Arisaka, .30-06 Springfield, or 7.62×51mm NATO), and therefore is regarded as being "intermediate" between traditional rifle and handgun cartridges.

As their recoil is significantly reduced compared to full-power cartridges, fully automatic rifles firing intermediate cartridges are relatively easy to control. However, even though they are less powerful than a traditional full-power cartridge, the external ballistics are still sufficient for an effective range of 300–600 metres (330–660 yd), which covers most typical infantry engagement situations in modern warfare. This allowed for the development of the assault rifle, a type of versatile selective fire small arms that is lighter and more compact than traditional battle rifles that fire full-power cartridges.