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.
Georgia–Persia relations
The consequences of these events came a few years later, when a new dynasty, the Qajars, emerged victorious in the protracted power struggle in Persia. Their head, Agha Mohammad Khan, as his first objective, resolved to bring the Caucasus again fully under the Persian orbit.
For Agha Mohammah Khan, the resubjugation and reintegration of Georgia into the Iranian Empire was part of the same process that had brought Shiraz, Isfahan, and Tabriz under his rule. He viewed, like the Safavids and Nader Shah before him, the territories no different than the territories in mainland Iran. Georgia was a province of Iran the same way Khorasan was. As the "Cambridge History of Iran" states, its permanent secession was inconceivable and had to be resisted in the same way as one would resist an attempt at the separation of Fars or Gilan. It was therefore natural for Agha Mohammad Khan to perform whatever necessary means in the Caucasus in order to subdue and reincorporate the recently lost regions following Nader Shah's death and the demise of the Zands, including putting down what in Iranian eyes was seen as treason on the part of the "wali" of Georgia.