The Cumans were the Turkic confederation that ruled the steppe from the Danube to the Volga in the eleventh to thirteenth centuries, fought and served every power around them, and were shattered by the Mongols in 1223.
The Cumans — Polovtsy to the Rus', Kipchaks in the Islamic sources — moved west across the steppe in the eleventh century and displaced the Pechenegs and the Oghuz from the grasslands north of the Black Sea.
They were never a state. What the sources call Cumania was a confederation of clans under their own khans, without a capital, a central authority or a written language, occupying the largest continuous grassland in Europe.
That did not make them marginal. For two centuries no war in the northern Balkans, the Rus' lands or the Hungarian plain was fought without Cuman cavalry on one side or both, and the Byzantine Empire owed them one of its most important victories.
Their organisation was the standard steppe pattern: clans grouped into larger units under khans, cooperating for large campaigns and operating separately the rest of the time.
They lived by herding, by raiding settled neighbours, by charging for passage, and increasingly by selling captives — and, in the end, by being sold themselves.
The stone figures they set over their burial mounds are the largest body of physical evidence they left: thousands of them once stood across the steppe, and they are the closest thing to a Cuman self-portrait that exists.
As with the Pechenegs, the named khans are the ones outsiders recorded, and the list reflects who fought whom rather than who mattered.
Tugorkan and Bönek are the khans who led the Cuman force at Levounion in 1091 and then spent the following decade raiding the Rus' — Tugorkan was killed outside Pereyaslavl in 1096, having in the meantime married his daughter to the prince of Kiev.
Köten is the last and most consequential: the khan who led the survivors of the Mongol invasion into Hungary in 1239, was granted lands in exchange for conversion, and was murdered in Pest by a mob who believed the Cumans were Mongol spies — shortly before the Mongols arrived and destroyed the Hungarian army at Mohi.
Their relationship with the Byzantine Empire was mercenary in the exact sense. In 1091 Alexios I hired forty thousand of them and destroyed the Pechenegs at Levounion; in other decades they raided the same frontier they had been paid to defend.
With the Rus' the relationship was continuous war and continuous intermarriage. Cuman raids are the background to a century and a half of Rus' history and to the Tale of Igor's Campaign, and several Rus' princes had Cuman mothers.
With Hungary it ended in settlement. The Cumans who fled the Mongols were given land in the Hungarian plain, and the region of Kunság still carries their name; their language survived there into the seventeenth century.
In 1223 a Mongol reconnaissance force under Jebe and Subutai came round the Caucasus and attacked the Cumans, who appealed to the Rus' princes for help.
The combined Cuman and Rus' army was destroyed at the Kalka River. It is the first encounter between the Mongols and either people, and it went badly enough to be remembered as a portent.
The full invasion came in 1237. Cumania was destroyed as a political entity, and the survivors split: some submitted and were absorbed into the Golden Horde, some fled to Hungary and Bulgaria, and very large numbers were sold into slavery.
The largest consequence was one nobody intended. Kipchak captives sold through the Black Sea slave markets became the military slaves of the Ayyubid sultans of Egypt, and in 1250 those Mamluks took the state for themselves.
The Mamluk sultanate that resulted was Kipchak in origin and ruled Egypt and Syria for two and a half centuries — it stopped the Mongols at Ain Jalut in 1260, and it was a Kipchak-born sultan, Baibars, who destroyed Antioch in 1268.
So a steppe confederation with no writing and no capital ended up supplying the dynasty that halted the Mongol advance and finished the last of the Byzantine east. The Codex Cumanicus, a phrasebook compiled by Italian merchants and German missionaries, is most of what survives of the language.