Question: What is the name of the geographical region that early Islamic usage often regarded everywhere east of western Persia and where Vistaham helped Khosrow regain his throne after the rebellion of Bahram Chobin?  
Sentence (from "Narses (general under Maurice)"): He attempted to salvage the situation with a diplomatic mission but was burned alive in Constantinople by Phocas' government after having been promised safety.
Relevant evidence: No