The proto-Ainu Satsumon followed up with an invasion into southern Sakhalin in the 11th to 12th century, leaving behind oral traditions telling how the Ainu defeated the Tonchi people there (likely the Okhotsk), and sent them fleeing north by boat. Thus the people who came to be known as the Ainu settled in southern Sakhalin while the Nivkhs kept to northern Sakhalin and the area around the Amur estuary on the mainland. Mongol interest in Northeast Asia As part of the Mongol conquest of the Jurchen Jin dynasty and Eastern Xia, the Mongols took political control of Manchuria in 1233. In response to raids by the Nivkh and the Udege peoples, the Mongols established an administration post at Nurgan (present-day Tyr, Russia) at the junction of the Amur and Amgun rivers in 1263, and forced the submission of the two peoples. The Mongols were motivated by their worldview that heaven had bestowed them the right to rule the whole world, thus unconquered people were naturally rebels upon whom military conquest was justified. The Mongols were also in the process of incorporating the Chinese tributary system for their own political and commercial purposes: the Mongols could manage relations with the peripheral peoples of Northeast Asia while making sure that goods from the region would be available as tribute or trade goods. Sable furs from lower Amur and Sakhalin, for instance, were especially favoured by the Mongol-Chinese upper class at the time. From the Nivkh perspective, their surrender to the Mongols essentially established a military alliance against the Ainu who had invaded their lands. In addition, some Japanese researchers ascribe another motivation to the Mongols in regards to their subjugation of Sakhalin. Calling the Sakhalin expeditions a "Mongol invasion from the north" (北からの蒙古襲来), proponents of this northern invasion theory connect the events in Sakhalin with the contemporaneous Mongol invasions of Japan in the south, and theorize that the Mongols were interested in a northern route into Japan through Manchuria and Sakhalin. Presumably, the Mongols would sail south from Sakhalin to Hokkaido and invade Honshu from there. However, there are no historical records or maps of the period that reveal a geographic knowledge that Sakhalin was anywhere near Japan, so any intention on the part of the Mongols to use Sakhalin as an entry point into Japan remains doubtful. Conflicts Expeditions into Sakhalin (1264–1286) Soon after receiving the surrender of the Nivkh, the