From 1264 to 1308, the Mongol Empire (and its successor the Yuan dynasty) made several incursions into the island of Sakhalin off the east coast of Siberia to aid their Nivkh allies against the Ainu, who had been expanding north from Hokkaido. The Ainu put up a tenacious resistance, even launching a counter-attack on Mongol positions on the continent across the Strait of Tartary in 1297, but finally capitulated to the Mongol-led Yuan dynasty of China in 1308. Background The peoples of Sakhalin The Nivkh people are believed to be the descendants of an indigenous population that inhabited Sakhalin island since the Neolithic period. During the 6th century AD, a confluence of Koryak culture from the north, the Heishui Mohe culture from the west, and indigenous Neolithic Sakhalin culture gave birth to the Okhotsk culture, which was characterized by fishing, sea-mammal hunting, pig breeding, and pottery. This culture expanded rapidly in the 7th century from Sakhalin: to the north, it took over the Kuril Islands and reached as far as the southern tip of the Kamchatka Peninsula; to the south, it crossed the La Pérouse Strait and met the Satsumon culture on the northern shores of Hokkaido. The Nivkh, being the dominant population of Sakhalin before the 12th century, are believed to be the bearers of the Okhotsk culture. The Nivkh are known in Chinese sources as "Jiliemi" (吉列迷), which became Russified as "Gilyak" in the modern era and later renamed to the endonym "Nivkh" in the 1930s. As a result of the northward expansion of the Yamato people in Honshu beginning in the 7th century AD, the Emishi were slowly assimilated into the dominant Japanese culture or pushed further north to the island of Hokkaido. The influx of migrants from Honshu to Hokkaido gave rise to the Satsumon culture in Hokkaido, which spread agriculture throughout the island save for the coast of the Sea of Okhotsk facing Sakhalin, which remained under the influence of the Okhotsk culture. Eventually, population pressure and the need for agricultural lands pushed the Satsumon, identified as one of the ancestors of the Ainu people, into warfare with the Okhotsk in the 10th to 11th century, causing the Okhotsk to retreat to Sakhalin. The conflicts of the period were reflected in the yukar oral traditions of the northern Hokkaido Ainu, in which the heroes of the "land people" (yaunkur) prevailed over the "sea people" (repunkur).