Explanation: In the early 7th century AD, the Byzantine and Sassanid Persian Empires engaged in a decades-long struggle against each other which resulted in the near-total depletion of their manpower, treasury, and domestic political support in a war that brought neither Empire any substantial gains.
Shortly thereafter, the Arab tribes, newly united under the newfangled faith of Islam, overran both polities, carving half of the Empire away from the Byzantines, and destroying the Sassanids entirely.
Explanation: In the early 7th century AD, the Byzantine and Sassanid Persian Empires engaged in a decades-long struggle against each other which resulted in the near-total depletion of their manpower, treasury, and domestic political support in a war that brought neither Empire any substantial gains.
Shortly thereafter, the Arab tribes, newly united under the newfangled faith of Islam, overran both polities, carving half of the Empire away from the Byzantines, and destroying the Sassanids entirely.