During the reign of Huizong, the Jurchen tribe to the north (once subordinates to the Liao), revolted against their Khitan masters. The Jurchen community already had a reputation of great economic clout in their own region of the Liao and Sungari rivers. They were positioned in an ideal location for horse raising, and were known to muster ten thousand horses a year to sell annually to the Khitans of the Liao dynasty. They even had a martial history of being pirates, in the 1019 Toi invasion of the Heian Japanese islands in modern-day Iki Province, Tsushima Province, and Hakata Bay. From the Jurchen Wanyan clan, a prominent leader Wanyan Aguda (1068–1123) challenged Liao authority, establishing their own Jin (or 'Golden') dynasty in 1115. The Song government took notice of the political dissidence of the Jurchens in Liao's territory, as Council of State Tong Guan (1054–1126) persuaded the emperor to ally with the Jurchens against the Liao . The two nations secretly forged the Alliance on the Sea, so-named because it was negotiated by envoys who crossed the Bohai Sea, and agreed to jointly invade the Liao, and if successful, divide up Liao territory with the Sixteen Prefectures given to the Song.