Sakhalin at this time, since ramparts of a Mongol-Chinese fort dated to the 13th century were discovered at Cape Crillon. The ramparts, called the Shiranushi earthwork (白主土城) by Japanese archaeologists, were markedly different from Ainu chashi and is the only fortification of a continental type found on Sakhalin. Japanese researcher Kazuyuki Nakamura believes that the Shiranushi site should be identified as the Guohuo fort (果夥) mentioned in the Yuan source Jingshi Dadian (經世大典, "Compendium for governing the world"), and that it was built by the Mongols to stem Ainu invasions from Hokkaido. The Ainu counterattack and the end of the conflict (1287–1308) To support the continual campaigns into Sakhalin, the Mongols established military-agricultural colonies near the Amur estuary around 1285, populating them with Han Chinese exiles of the newly-extinguished Song dynasty. This did not last long, however, as the rebellion of the Mongol prince Nayan in Manchuria forced the troops to withdraw from the Amur region in 1287. Perhaps reflecting the diminishing Mongol influence in the area, two Nivkh who had been centurions (百戶) in the Mongol military defected to the Ainu in 1296, and the next year an Ainu force under the chieftain Waying (瓦英) crossed the strait on Nivkh boats and raided settlements on the continent. The Nivkh that were still aligned with the Mongols warned that the Ainu planned to cross the sea from Guohuo when the sea freezes, and that they were going to attack the falconers of the Amur estuary. These falconers, which included some Nivkh, were targeted by Ainu raiders for their falcons—the feathers were an exotic trade good—and for their supplies from China due to their status as slaves of the Mongol imperial court. Thus warned, when the Ainu invaded the Amur estuary in mid-1297, the Mongols caught up with them and defeated the invading Ainu near Lake Kizi. The Ainu were recorded to have made one more raid on the continent in 1305, which evaded the Mongol army. In 1308, the Ainu chieftains Waying and Yushannu (玉善奴) communicated through the Nivkh that they desired to surrender. The Ainu sent an ambassador to Nurgan with gifts of swords and armours and promised to pay a tribute of furs every year. With this, the war between the Ainu and the Mongols was over. Aftermath The Mongol invasions represented the first time the influence of a regime based in China was directly extended to Sakhalin.