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.
Monarch
In modern history, between 1925 and 1979, Iran was ruled by two Emperors from the Pahlavi dynasty that used the title of "Shahanshah" (or "King of Kings"). The last Iranian Shahanshah was King Mohammad Reza Pahlavi, who was forced to abdicate the throne as a result of a revolution in Iran. In fact Persian (Iranian) kingdom goes back to about 2,700 BC (see List of Kings of Persia), but reached its ultimate height and glory when King Cyrus the Great (Known as "The Great Kourosh" in Iran) started the Achaemenid dynasty, and under his rule, the empire embraced all the previous civilized states of the ancient Near East, expanded vastly and eventually conquered most of Southwest Asia and much of Central Asia and the Caucasus. From the Mediterranean sea and Hellespont in the west to the Indus River in the east, Cyrus the Great created the largest empire the world had yet seen.