Much of the Grand Canal south of the Yellow River was ruined for several years after 1128 when Du Chong decided to break the dykes and dams holding back the waters of the Yellow River in order to decimate the oncoming Jurchen invaders during the Jin–Song wars. The Jurchen Jin dynasty continually battled with the Song in the region between the Huai River and the Yellow River; this warfare led to the dilapidation of the canal until the Mongols invaded in the 13th century AD and began necessary repairs.