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.
Iranian peoples
During the 1st centuries of the 1st millennium BCE, the ancient Persians established themselves in the western portion of the Iranian plateau and appear to have interacted considerably with the Elamites and Babylonians, while the Medes also entered in contact with the Assyrians. Remnants of the Median language and Old Persian show their common Proto-Iranian roots, emphasized in Strabo and Herodotus' description of their languages as very similar to the languages spoken by the Bactrians and Sogdians in the east. Following the establishment of the Achaemenid Empire, the Persian language (referred to as ""Farsi"" in Persian) spread from Pars or Fars Province to various regions of the Empire, with the modern dialects of Iran, Afghanistan (also known as Dari) and Central-Asia (known as Tajiki) descending from Old Persian.