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.
Tajiks
The dialects of modern Persian spoken throughout Greater Iran have a common origin. This is due to the fact that one of Greater Iran's historical cultural capitals, called Greater Khorasan, which included parts of modern Central Asia and much of Afghanistan and constitutes as the Tajik's ancestral homeland, played a key role in the development and propagation of Persian language and culture throughout much of Greater Iran after the Muslim conquest. Furthermore, early manuscripts of the historical Persian spoken in Mashhad during the development of Middle to New Persian show that their origins came from Sistan, in present-day Afghanistan.