靖康之变
However, the poor performance and military weakness of the Song army was observed by the Jurchens, who immediately broke the alliance, beginning the Jin–Song Wars of 1125 and 1127. Because of the removal of the previous defensive forest, the Jin army marched quickly across the North China Plain to Kaifeng. In the Jingkang Incident during the latter invasion, the Jurchens captured not only the capital, but the retired emperor Huizong, his successor Emperor Qinzong, and most of the Imperial court.