At the end of the 13th century, Sagaing was the northernmost vassal state of Myinsaing, the polity that succeeded Pagan in Central Burma. The northern province included the Mu valley, one of the three main granaries of the Irrawaddy valley. To the north of Sagaing lay the Province of Zhengmian of the Mongol Empire—present-day northern Burma and southwestern Yunnan, which the Mongols had wrested away from the Pagan Empire since the 1280s. The Mongols launched another invasion in 1300–01 but could not break through and quit northern Burma altogether in 1303.