Firearm a battle rifle such as the Karabiner 98k, but the chief differences defining an assault rifle are select-fire capability and the use of a rifle round of lesser power, known as an intermediate cartridge. Soviet engineer Mikhail Kalashnikov quickly adapted the German concept, using a less-powerful 7.62×39mm cartridge derived from the standard 7.62×54mmR Russian battle rifle round, to produce the AK-47, which has become the world's most widely used assault rifle. Soon after World War II, the Automatic Kalashnikov AK-47 assault rifle began to be fielded by the Soviet Union and its allies in the Eastern Bloc, as well as
AK-74 launchers. Throughout its development and evaluation stage the multiple modifications were applied to meet Russian military standards, as well as to improve upon the "range of defects" that were discovered on prototype models and to addresses concerns regarding the cost of earlier prototypes. In September 2016 the prototype models were replaced by the final production models of the AK-12 (chambered in 5.45×39mm]) and AK-15 (chambered in 7.62×39mm) assault rifles. Parallel developments are the RPK-16 light machine gun and the MA compact assault rifle (both chambered in 5.45×39mm). The AK-12, AK-15, RPK-16 and MA production models technically stronger resemble the AK-74M,