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.
Iran–Russia relations
In his later years of rule, Peter the Great found himself in a strong enough position to increase Russian influence more southwards in the Caucasus, the Caspian Sea and the Black Sea at the cost of the two declining empires; the Safavid Empire and the Ottoman Empire. He made the city of Astrakhan his base for his hostilities against Persia, created a shipyard, and attacked the weakened Safavids in the Russo-Persian War (1722-1723), capturing many of its territories in the Caucasus and northern mainland Iran for several years. After several minor years of political chaos in Persia following the abolishment of the Safavids, a new mighty Persian empire was born under the military genius of fortune, Nader Shah. Fearing a costly war which would most likely be lost against Nader and also being flanked by the Turks in the west, the Russians were forced to give back all territories and retreat from the entire Caucasus and northern mainland Iran as according to the Treaty of Resht (1732) and Treaty of Ganja (1735) during the reign of Anna of Russia. The term of the treaty also included the first fact of close Russo-Iranian collaboration against a common enemy, in this case the Ottoman Turks.