The video gave adequate credit Khalid ibnWaliid and other key liberators of Iran and Egypt. The video dwelled too much on battle tactics. They did not emphasize the fact the Iran and Egypt hated the oppression they suffered under Hiraqla and Kusra respectively.
Naturally those tyrannized tribes/nations defected. Instead of calling it an Arab conquest it should be called Iranian/Iraqi/Egyptian liberation of their territories with help from Khulafa'aRraashidiin. Its why I remind
@Apollo that the modern day decedents of those nations are ethnically different from Xijaaj/Najd, actually closer to modern day speakers of Suryani language and Arabic speaking CopticMasiixis