 These can be compared to the even shorter, less-powerful assault rifle, which might be considered the "carbine branch of weapons development", although indeed, there are now carbine variants of many of the assault rifles which had themselves seemed quite small and light when adopted.By the 1960s, after becoming involved in War in Vietnam, the US did an abrupt about-face and decided to standardize on the intermediate 5.56×45mm round (based on the .223 Remington varmint cartridge) fired from the new, lightweight M16 rifle, leaving NATO to hurry and catch up.Many of the NATO countries couldn't afford to re-equip so soon after the recent 7.62mm standardization, leaving them armed with full-power 7.62mm battle rifles for some decades afterwards, although by this point, the 5.56mm has been adopted by almost all NATO countries and many non-NATO nations as well.