Aiouki reigned about fifty years. After his death, in 1724, the old dissensions broke out again among the Kalmucks; Russia made good use of the opportunity to break down the independence of the hordes by directly interfering in their domestic affairs, and their princes soon became subject to the imperial sceptre. Thenceforth the dignity of khan was conferred only by the Muscovite tzars, and the tribes were put under the special control of a Russian commander called a pristof.
After a long series of contests and intrigues, Dondouk Ombo, the son-in-law of Aiouki, was named khan, to the prejudice of Aiouki's grandson. Under this prince internal peace was restored among the hordes, and the Kalmucks did good service to Russia in the campaigns against the Nogais, and other inhabitants of the Kouban. But quarrels broke out again on the death of Dondouk Ombo in 1741. His children, who were minors, were set aside, and his ambitious and intriguing widow contrived to have Dondouk Dachi, her youngest brother, and grandson of the celebrated Aiouki, declared vice-khan. The new chief was entirely devoted to Russia, and his submissiveness was rewarded after the lapse of fifteen years by promotion to the rank of khan; but he enjoyed that dignity only four years. His son Oubacha succeeded him as vice-khan in January, 1761.
In Oubacha's reign new hordes arrived in Europe, and the Kalmucks were reinforced by 10,000 tents, commanded by Chereng Taidchi. The various tribes, which consisted of more than 80,000 families, and possessed innumerable herds of cattle, extended at that time from the shores of the Jaik to the Don, and from Zaritzin, on the Volga, to the foot of the northern slopes of the Caucasus. Oubacha paid no tribute to Russia; he was regarded rather as an ally than a vassal, and was only required to supply cavalry to the imperial armies in time of war.
Oubacha vigorously seconded the Russians in their expedition against the Turks and Nogais. His army amounted to 30,000 horse, and one of its detachments figured even in the celebrated siege of Otchakof. It was on the return of the Kalmucks from these campaigns that their celebrated emigration took place, when nearly half a million of men, women, and children, headed by their prince, quitted the banks of the Volga with their cattle, and set out across the most arid regions in quest of their old country.
The flight of the Kalmucks has been variously explained. B. Bergmann attributes it solely to the vindictiveness of Zebeck Dorchi, a relation of Oubacha's, who had been frustrated in his attempt to raise himself to sovereign power. After fruitless attempts at the court of the Empress Elizabeth, he had nevertheless been named first sargatchi, or councillor at the court of his rival. The imperial government hoped by this means to curb the ambition of Oubacha, whose power it had abridged in 1761, by deciding that the sargatchis, or members of the khan's council, should be attached to the ministry of foreign affairs, with an annual salary of 100 rubles. According to Bergmann, Zebeck Dorchi made no account of his new dignity, and unable to forgive Russia for not having favoured his pretensions, he joined the hordes with a full determination to take signal vengeance. He would induce the Kalmucks to go over to China, and thus deprive the empire of more than 500,000 subjects, and the army of the greater part of its best cavalry, and make all the neighbouring towns feel severely the loss of their cattle. Such, according to Bergmann, was Zebeck Dorchi's project, to realise which he counted solely on the natural fickleness of the Kalmucks, and his own active intrigues. This was certainly a very extraordinary scheme of vengeance, and one we can hardly credit, notwithstanding Bergmann's assertions. Zebeck Dorchi's aim being to secure the supreme power, it would have been folly for him to choose such means. It would have been much more to the purpose to have informed against Oubacha at the moment when the latter was making his arrangements for quitting Russia. Such a service would have had its reward, and the informer would undoubtedly have supplanted his rival. This whole explanation of the affair given by Bergmann, rests on no one positive fact, and can only have been devised by a man writing under Russian influence, and consequently forced to disguise the truth.