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.
Greater Iran
Throughout history, Iran always had strong cultural ties with the region of nowadays Iraq. Mesopotamia is considered as the cradle of civilization and the place where the first empires in history were established. These empires, namely the Sumerian, Akkadian, Babylonian, and Assyrian, dominated the ancient middle east for millennia, which explains the great influence of the Mesopotamia on the Iranian culture and history, and it is also the reason why the later Iranian and Greek dynasties chose Mesopotamia to be the political centre of their rule. For a period of around 500 years, what is now Iraq formed the core of Iran, with the Iranian Parthian and Sasanian empire having their capital in what is modern-day Iraq for the same centuries long time span. (Ctesiphon)