The Proto-Iranians, a branch of the Indo-Iranians, emerged in Central Asia around the mid-2nd millennium BCE.^[9] This era marked the distinction of the Iranian peoples, who expanded over a vast region, including the Eurasian Steppe, from the Danubian plains in the west to the Ordos Plateau in the east and the Iranian Plateau in the south​.^[10]

The historical records become clearer with the Neo-Assyrian Empire's accounts of interactions with tribes from the Iranian plateau. This influx of Iranians led to the Elamites losing territories and retreating to Elam, Khuzestan, and nearby areas.^[11] Bahman Firuzmandi suggested that southern Iranians might have mixed with the Elamite populations in these regions.^[12] In the early centuries of the first millennium BCE, ancient Persians, established in the western Iranian Plateau. By the mid-first millennium BCE, ethnic groups such as the Medes, Persians, and Parthians were present on the Iranian plateau, but they remained under Assyrian control like much of the Near East until the Medes rose to prominence. During this period, parts of what is now Iranian Azerbaijan were part of Urartu. The emergence of significant historical empires like the Medes, the Achaemenid, Parthian, and Sasanian Empires marked the beginning of the Iranian Empire in the Iron Age.