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.
Parthia
Parthia ( "Parθava"; "Parθaw"; "Pahlaw") is a historical region located in north-eastern Iran. It was conquered and subjugated by the empire of the Medes during the 7th century BC, was incorporated into the subsequent Achaemenid Empire under Cyrus the Great in the 6th century BC, and formed part of the Hellenistic Seleucid Empire following the 4th-century-BC conquests of Alexander the Great. The region later served as the political and cultural base of the Eastern-Iranian Parni people and Arsacid dynasty, rulers of the Parthian Empire (247 BC – 224 AD). The Sasanian Empire, the last state of pre-Islamic Persia, also held the region and maintained the Seven Parthian clans as part of their feudal aristocracy.