List of ancient great powers
The Sassanid Empire is the name used for the fourth Iranian dynasty, and the second Persian Empire (226–651). The empire's territory encompassed all of today's Iran, Iraq, Armenia, Afghanistan, eastern parts of Turkey, and parts of Syria, Pakistan, and large parts of Caucasia, Central Asia and Arabia. During Khosrow II's rule in 590–628 Egypt, Jordan, Palestine, Lebanon were also briefly annexed to the Empire, as well as far west as western Asia Minor. The Sassanid era, encompassing the length of the Late Antiquity period, is considered to be one of the most important and influential historical periods in Iran. In many ways the Sassanid period witnessed the highest achievement of Persian civilization. The empire is furthermore known for being the arch-rival of the neighboring Roman–Byzantine Empire for a period of over 400 years. As the Parthians were replaced by the Sassanids, they carried on the already century long lasting Roman–Persian Wars, which would eventually become the longest conflict in human history.
Fall of the Sasanian Empire
The Sasanian era is one of the most influential periods in Iran's history. It also marks the third rise of a great Iranian empire, a dynasty that rivaled its predecessor, the Achaemenids, who too, like the Sassanids, were native to the province of Pars, and in some instances the Parthians, in glory and power. Although it fought many campaigns against the Romans/Byzantines in the west and the nomadic people in the east and north, the Sasanian Empire met its demise not by the Byzantine-Roman Empire, but by emerging Arab Muslims from across its southern borders. However, the conflict with the Byzantines greatly contributed to its weakness, by draining Sassanid resources, leaving it a prime target for the Muslims.