From Caucasus: An Introduction, by Thomas de Waal (Oxford U. Press, 2010), Kindle Loc. 418-459:
Persian culture can be traced in the South Caucasus from the sixth century BC, and Persians colonized large parts of the region for roughly a thousand years, far longer than the Russians did. The cultural residue of this is surprisingly faint but is there if one looks for it. The Armenian language is so full of Persian loan-words that it was long thought to be an Iranian, not an Indo-European language. The historian Nina Garsoïan argues that the Armenian sociopolitical system, with its tradition of hereditary aristocrats and semidivine monarchy, derived from an Iranian tradition. Medieval Georgia’s “Golden Age” was also heavily Persianized. Shota Rustaveli, author of the famous twelfth-century epic The Knight in the Panther Skin called his poem “a Persian work now done into Georgian.” Georgian princes served the Safavid dynasty for three centuries.
The Persian-Iranian influence is strongest in Azerbaijan. The river Araxes only became a noticeable border in the nineteenth century. Prior to that, the lands to the north and south were generally part of the same kingdoms. The Azerbaijani city of Ganzak (Ganja) was the location of one of the four great fires of the Zoroastrian religion. The twelfth-century poet Nizami of Ganja is revered as a great Azerbaijani cultural icon, even though he wrote in the Persian language. In the sixteenth century, the Safavid Empire could lay claim to being a sort of proto-Azerbaijani state. The founder of the empire, Shah Ismail I (ruled 1501–24), came from Ardebil in what is present-day northern Iran, not far from Azerbaijan. Of mixed ethnic descent, he spoke both Persian and Azeri (or at least a form of Turkish that evolved into what is now Azeri) and wrote poems in Azeri under the name Khatai. In Safavid times, an estimated twelve hundred Azeri words, mainly dealing with administrative and military issues, entered the Persian language.
Iranian political dominance of the Caucasus began to fade with the end of the Safavids in 1722. A succession of military defeats on all fronts led to a slow retreat from the Caucasus that culminated in full capitulation to the Russians in 1828. This marked what some Azerbaijanis call “the parting of the ways” between northern and southern Azerbaijan. The Caucasus lived on in the assumptions of some Iranian statesmen, even as it turned into a Russian zone of influence. At the Versailles peace conference at the end of the First World War, the Iranian delegation caused consternation when it handed the conference a memorandum laying claim to all of present-day Armenia and Azerbaijan and parts of Dagestan. The document explained, “these provinces must be returned to Persia, for they had already formed part of Persia.”
Currently, Iran is closer to Armenia than to either Azerbaijan or Georgia. One of Armenia’s two open borders is with Iran, and an Iranian-Armenian gas pipeline, opened in 2007 gave the Armenians a new source of natural gas. For Azerbaijan and Iran, the big sleeping issue is Iran’s large population of ethnic Azerbaijanis in the north of the country, who may number as many as twenty-five million—or three times the number of Azerbaijanis in the Republic of Azerbaijan. So far, there has been no mass movement there for closer political ties to the north. Fred Halliday writes that after 1979, “in an upheaval in which many dogs barked, Azerbaijani nationalism is the one dog that did not, at least during the first 15 years after the Islamic revolution.” Iran would undoubtedly like to play a bigger part in the South Caucasus, but the biggest deterrent to it doing so is Western pressure. If there is a thaw between Iran and the West over the nuclear issue, then Tehran can be expected to claim a role in the region again.