Cimmerians are known from historical records to have invaded Anatolia around this period, while the Thracians are mentioned as far back as the Iliad and Odyssey, where they participate in the Trojan War; Thracologists and archaeologists generally trace back the Thracians to the Balkan/Carpatho-Danubian Chalcolithic period (Hoddinott et al.).
It is sometimes assumed that the migration of the Cimmerians was triggered by an Iranian expansion, from the area of the former Srubna culture, into the steppes of what is now the Ukraine. Virtually nothing is known about the Cimmerian language, but they are usually speculated to belong to the Satem group on the basis of royal names such as Sandrakshatra. The Thracian language is poorly attested, but available vocabulary suggests a Satem branch, though theories of a Thracian-Iranian branch have been all but discarded, and no close link between Thracian and Iranian has been demonstrated. The Sigynnae, reported by classical authors as a tribe of the Black Sea steppes related to the Medes, may have invaded the area about the time of the Cimmerian expansion.
Archaeologically, "Thraco-Cimmerian" artefacts are metal (usually bronze) items, particularly parts of horse tacks, found in a late Urnfield context, but without local Urnfield predecessors for their type. They appear rather to spread from the Koban culture of the Caucasus and northern Georgia, which together with the Srubna culture, blends into the 9th to 7th centuries pre-Scythian Chernogorovka and Novocherkassk cultures, and by the 7th century, "Thraco-Cimmerian" objects are spread further west over most of Eastern and Central Europe, locations of finds reaching to Denmark and eastern Prussia in the north and to Lake Zürich in the west. Together with these bronze artefacts, earliest Iron items appear, ushering in the European Iron Age, corresponding to the Proto-Celtic expansion from the Hallstatt culture.
The artifacts labelled "Thraco-Cimmerian" all belong to a category of upper class, luxury objects, like weapons, horse tacks and jewelry, and they are recovered only from a small percentage of graves of the period. From this it is assumed that the "Thraco-Cimmerian" migration did not consist of large populations, but rather of relatively small groups who installed themselves as ruling class over the indigenous Urnfield/Hallstatt population.