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.
Azerbaijan (Iran)
Following military defeats at the hands of the Russian Empire, Qajar Persia ceded all of its territories in the North Caucasus and Transcaucasia to Russia via the Treaty of Gulistan of 1813 and the Treaty of Turkmenchay of 1828. The territories south of the Aras River, which comprised the region historically known as Azerbaijan, became the new north-west frontier of the Persian Empire and later Iran. The territories north of the Aras River, which were not known by the name Azerbaijan at the time of their capture by Russia, were absorbed into the Russian Empire, renamed the Azerbaijan Democratic Republic during the country's short-lived independence from 1918 to 1920, incorporated into the Soviet Union as the Azerbaijan Soviet Socialist Republic, and finally became the independent Republic of Azerbaijan when the Soviet Union dissolved.