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
German military rifles designed in 1945 by Sergei Gavrilovich Simonov. It is formally known as the "Samozaryadniy Karabin sistemi Simonova" (Russian: Самозарядный карабин системы Симонова), 1945 (Self-loading Carbine, Simonov's system, 1945), or SKS 45. It was originally planned to serve as the standard issue weapon for the Soviet military forces, alongside the new AK-47. As mass production of AK-pattern rifles increased, the SKS carbine was soon phased out of service. It was quickly replaced entirely by the AK-47, but it remained in second-line service for decades afterwards. The AK-47 is a gas-operated assault rifle used in most Eastern bloc countries including East Germany