Caucasian Albania was the area of modern-day Azerbaijan. It was a client state of the Roman Empire for four centuries around the time of Christ. Its influence over the region started in the first century before Christ and lasted until around 250 AD. Around 299 AD, Albania was again a "nominal" vassal state of emperor Diocletianus for a few years more.
Rome controlled Caucasian Albania only as a client or vassal state. It was never able to fully make it a part of the Roman Empire, like a "province" (as happened with its neighbour, Armenia).
In these centuries Rome brought Christianity to the Caucasian Albanians, with a western cultural influence that has lasted until contemporary Azerbaijan. Even if few Azerbaijanis are Christians today, the writing system they use is the Roman alphabet.
A second and final influence came from the Eastern Roman Empire when emperor Heraclius was able to take control of Caucasian Albania in 627 AD with help from the Gokturks of the Western Turkic Khaganate, in the Third Perso-Turkic War.
History
There was an enduring relation between Caucasian Albania and Ancient Rome. In 65 BC, the Roman general Pompey, who had just subjugated Armenia and Iberia and had conquered Colchis, entered Albania at the head of his army. Crossing the arid province of Cambysenē (Kambičan)—recently seized from the Armenians by the Albanians—he turned in the direction of the Caspian Sea.
In fording the Alazan river, he clashed with the forces of Oroezes, king of Albania, and eventually defeated them. Pompey ensured the control of Albanians nearly reaching the Caspian sea before returning to Anatolia.
But the Albanians, influenced by the Parthian Empire were not slow to revolt against Rome: in 36 BC Mark Antony found himself obliged to send one of his lieutenants to bring an end to their rebellion. Zober, who was then king of Albania, capitulated and Albania thus became -at least in name- a "Roman protectorate", starting a condition of vassalage that lasted for nearly three centuries.
A king of Albania appears in the list of dynasties whose ambassadors were received by Augustus.
In 35 AD King Pharasmanes of Iberia and his brother Mithridates, with the support of Rome, confronted the Parthians in Armenia: the Albanians proved effective allies, contributing to the defeat and temporary eviction of the Parthians.
Emperor Nero prepared in 67 AD a military expedition in the Caucasus: he wanted to defeat the barbarian Alans and conquer for Rome all the northern shores of the Black sea from actual Georgia-Azerbaijan to what is now Romania-Moldavia, but his death stopped it.
Successively Vespasian was determined to restore and reinforce the full authority of Rome in the Caucasus as far as the Caspian.
The presence of a detachment of the Legio XII Fulminata at a distance of some kilometers from the shores of that sea (69 km south of Baku) is attested by an inscription drawn up between 83 and 96 AD in the reign of Domitian.
In 75 AD, XII Fulminata was in Caucasus, where Emperor Vespasian had sent the legion to support the allied kingdoms of Iberia and Albania.
An inscription has been found in Azerbaijan which reads: IMP DOMITIANO CAESARE AVG GERMANICO LVCIVS IVLIVS MAXIMVS LEGIONIS XII FVL, Under imperator Domitian, Caesar, Augustus Germanicus, Lucius Julius Maximus, Legio XII Fulminata.
Some historians argue that the actual settlement of Ramana near Baku was possibly founded by the Roman troops of Lucius Julius Maximus from "Legio XII Fulminata" in the first century AD and derives its name from the Latin Romana.
Among the facts that strengthen this hypothesis are the military-topoghraphical map of Caucasus published in 1903 by Russian Administration which spells name of town as "Romana", various Roman artefacts found in the Absheron region and also old inhabitants' referring to the town as Romani.
Additionally, Ramana is positioned in an area perfectly suited for a Roman "castrum" to control nearby Baku' s port, on the commercial sea route (through the Caspian sea) between the Caucasus and the Central Asia plains.
Despite the growth of Roman influence, Albania never ceased to remain in commercial and probably also cultural contact with Persia, but with Trajan in 114 AD Roman control over Caucasian Albania was nearly complete with top social levels fully romanized.
During the reign of Roman emperor Hadrian (117-138) Albania was invaded by the Alans, an Iranian nomadic group.