Mongols received reports of the Nivkh being invaded yearly by the peoples of the east, namely the Guwei (骨嵬) and the Yiliyu (亦里于). "Guwei" was the name that the Nivkh used to refer to the Ainu people, while "Yiliyu", which means "deer" in Tungusic languages, could refer to any of the Tungusic peoples like the ancestors of the Sakhalin Uilta. The Mongols attacked the Ainu on Sakhalin on 30 November 1264, but the Ainu returned the next year to attack the Nivkh, killing some of their warriors. This time, however, the Mongols only sent supplies of food and weapons. Following the formal establishment of the Mongol Yuan dynasty in China in 1271, Taxiala (塔匣剌) of the Mongol eastern expedition army attempted to invade Sakhalin in 1272 and 1273, but he was not able to cross the raging Strait of Tartary. Seeking the advice of the local Udege people around Nurgan, Taxiala was told that he must wait for the strait to freeze in the winter months, then he could march his army across the ice into Sakhalin where he would find the lands of the Nivkh and the Ainu. This was certainly possible since the strait was only about four miles wide at its narrowest point, and the Ainu and Nivkh had long made use of this fact. Armed with this knowledge, Taxiala petitioned the Yuan court for another expedition against the Ainu in 1273, but this was rejected. However, the Mongols appeared to have learned the lesson, as subsequent Mongol expeditions into Sakhalin all happened during winter months. The next record of an invasion on the Ainu was in 1282, when Jurchens under Mongol rule were sent to aid the war effort by making boats to ship supplies across the sea. In 1284, a Mongol expedition was postponed from September to November out of fears that the windy seas might topple the supply boats. Following that campaign, the Mongols sent large armies up to 10,000 men for the expeditions of 1285 and 1286. Led by Tata'erdai (塔塔兒帶) and Yangwuludai (楊兀魯帶), the expeditions sailed across the sea in 1000 small boats carrying 10 men each. Judging by the relatively small population of the Sakhalin Ainu in later centuries, it is unlikely that the Ainu could have mustered a force large enough to defeat the Mongols with such numbers in open combat. The Mongol armies apparently reached the southern tip of