The ethnogenesis of the Gagauz is undetermined. As of now, neither native nor foreign specialists have been able to determine it, although twenty hypotheses have been suggested. Many of these begin with either/or questions: Who were the Gagauz—Turkicized Christians or Christianized Turks? That is, were they Bulgars who adopted the Turkish language or Turks who converted from Islam to Orthodoxy? Did they descend from pastoralists, or were they a sedentary population that was assimilated by pastoralists?
Answering these questions is made difficult by two factors: the absence of information in the literary chronicles of the Middle Ages, and the heterogeneous nature of the Gagauz population on the Balkan Peninsula on the eve of their relocation under the protection of Russia.
Much of the early ethnic history of the Gagauz took place on the boundaries between what was to become pastoralist steppe country and land inhabited by settled peoples. On the eve of their relocation to Bessarabia, the Gagauz in the Balkans consisted of two ethnic strands: the Khasyl Gagauz (the ancestors of true Gagauz) and the "Bulgarian Gagauzy." The majority of scholars are inclined to think that the original core of the Gagauz consisted of Turkic-speaking pastoral Oguz, Pechenegs, and Polovtsians. One of the last migrations of Polovtsians to the Balkans took place in 1241. But there is evidence that among them were Bulgars who had learned Turkish and a portion of a population then under the protection of the Turkish sultan, Izzedin Keikavus. In European scholarship the question has frequently been posed as to whether the most likely ancestors of the Gagauz were Turkic-speaking Proto-Bulgars who, in the 670s, came to the Balkans from the banks of the Volga under the banner of the Bulgar king, Asparukh.
In the course of the frequent Russo-Turkish wars at the end of the eighteenth and the beginning of the nineteenth centuries, the Gagauz, siding with the Russian army, emigrated to the steppe of southern Bessarabia, primarily within the bounds of the Bendersky and Izmailsky districts. In 1861 to 1862, some Gagauz settled in the Tavrid District.
The wave of Stolypin agrarian politics carried some Gagauz to Kazakhstan between 1912 and 1914, and later yet another group settled in Uzbekistan during the very troubled years of initial collectivization. So as not to lose their civil rights, they called themselves "Bulgars" in the 1930s; The Gagauz of the village of Mayslerge in the Tarhkent District retain that designation to this day.