The Soviet Union was inspired to create the 5.45x39mm round after the U.S. debuted the 5.56x45mm (the NATO version of the .223 Remington) during the Vietnam War with the M16. After being on the receiving end of the M16, the Soviets wanted to create a smaller caliber firearm that what was chambered for the 7.62x39mm like the AK-47. Along with the 5.45, the Soviets created the AK-74 carbine which was lighter and significantly more accurate than the larger bore rifle.