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.
Khorasan Province
The name "Khorāsān" (lit. "sunrise"; "East"; or "land of the rising sun") was originally given to the eastern province of Persia during the Sassanian period. The old Iranian province of Khorasan roughly formed the western half of the historical Greater Khorasan, a region which included parts that are today in Iran, Afghanistan, Tajikistan, Turkmenistan and Uzbekistan. Some of the main historical cities of Persia are located in the older Khorasan: Nishapur and Tus (now in Iran); Merv and Sanjan (now in Turkmenistan); Samarkand and Bukhara (both now in Uzbekistan); Herat and Balkh (now in Afghanistan); and Khujand and Panjakent (now in Tajikistan). The term was also used from the late middle ages–especially in post-Mongol (Chagatai and Timurid) times–to distinguish the region from neighbouring Transoxiana. The modern Iranian boundaries of the province of Khorasan were defined and formalised in the late nineteenth century.