Caucasian Albanians Early invaders included the Scythians in the 9th century BCE.[3 The South Caucasus was eventually conquered by the Achaemenids around 550 BCE. During this period, Zoroastrianism spread in Azerbaijan. The Achaemenids in turn were defeated by Alexander the Great in 330 BCE. Following the decline of the Seleucids in Persia in 247 BCE, an Armenian Kingdom exercised control over parts of modern Azerbaijan between 190 BCE to 428 CE. Sassanids made the kingdom a province in 252 CE. Caucasian Albania's ruler, King Urnayr, officially adopted Christianity as the state religion in the 4th century CE, and Albania would remain a Christian state until the 8th century. Sassanid control ended with their defeat by MuslimArabs in 642 CE.
The successive migration and settlement of Eurasian and Central Asian nomads continued to be a familiar pattern in the history of the Caucasus since ancient times, from the era of Sassanid-Persian empire to emergence of Azerbaijani Turks by the 20th century CE