In areas which were previously under Persian or Byzantine rule , the Caliphs lowered taxes , provided greater local autonomy , greater religious freedom for Jews , indigenous Christians , and brought peace to peoples that were demoralized and disaffected by the casualties and heavy taxation that resulted from the years of Byzantine-Persian warfare . In areas which were previously under Sassanid Persian or Byzantine rule , the Caliphs lowered taxes , provided greater local autonomy ( to their delegated governors ) , greater religious freedom for Jews , and some indigenous Christians , and brought peace to peoples demoralized and disaffected by the casualties and heavy taxation that resulted from the decades of Byzantine-Persian warfare .