During the rise of Genghis Khan in the 12th to 13th centuries, neither the Selenge valley in today's southern Buriatia or the Aga steppe had at this time any connection with the Buriats; these were the lands of the Merkid tribe and the Mongol tribe proper. Starting 1628 with the Russian Conquest and Buriat Migration, the Selenge Valley, as before, was inhabited by Mongol clans under the rule of the Khalkha khans. By 1652 the Khalkha khans were protesting the Russian incursions into Transbaikalia, and from 1666 on Khalkha raiding parties reached as far as Bratsk, Ilimsk, Yeravninsk, and Nerchinsk, while the khans besieged the forts on the Selenge. At the same time, however, the Khoris along the Uda River in 1647 surrendered as a block to the Russians to escape paying tribute to the Khalkhas. Smaller Mongol clan fragments also defected north to the protection of Cossack forts. The invasion of Khalkha by Galdan Boshogtu Khan in 1688 stopped Khalkha resistance to the Cossack advance and sent more Mongol refugees fleeing into Russian control.