Lasting from 92 BC to 627 AD, the conflict between the Persian and Roman Empires was a protracted struggle which was arguably a continuation of the Greco-Persian Wars. The Roman-Persian Wars led to weakening of the neighboring Arab states to the South and East of the Eastern Roman Empire. The conflict so drained both the Persian and Byzantine empires that once the conquests of Muhammad started, neither could mount an effective defense against the onslaught.