Some articles on sassanid:

Siege Of Jerusalem (637) - Prelude
... Just 23 years prior to the Muslim conquest, in 614, it fell to an invading Sassanid army under Shahrbaraz during the last of the Byzantine-Sassanid Wars ... initiated a war of conquest in the east by invading Iraq, then a province of the Sassanid Persian Empire while on the western front, his armies invaded the Byzantine Empire ...