Simplify the following text for a Grade 13 native English-speaking person.
Original: He has the distinction of being undefeated in over a hundred battles , against the numerically superior forces of the Byzantine-Roman Empire , Sassanid-Persian Empire , and their allies , in addition to other Arab tribes .
Simplified: He was undefeated in over a hundred battles against the numerically superior forces of the Byzantine Roman Empire , Sassanid Persian Empire , and their allies .