Simplify the following text for a Grade 14 native English-speaking person.
Original: The Sassanid Empire , which succeeded the Parthian Empire , was recognized as one of the two main powers in Western Asia and Europe , alongside the Roman Empire and its successor , the Byzantine Empire , for a period of more than 400 years .
Simplified: The Sassanid Empire , which succeeded the Parthian Empire , was recognized as one of the two main powers in Western Asia , alongside the Roman Empire and later the Byzantine Empire , for more than 400 years .