But, back to the wiki page on assault rifles...I thought this was interesting:
The assault rifle became the standard military rifle in the post-World War II era. The Soviet Union was the first nation in the post-war era to adopt an assault rifle, the AK-47, and other nations followed later.
B-b-b-but whaddabout the good ol' M2 Carbine, in service in WWII (end of)? I think it meets the definition of "assault rifle". Pre-dates the AK by a few years.