 After reigning for barely one month , Zhang Bangchang was persuaded by the Song to step down as emperor of the Great Chu and to recognize the legitimacy of the Song imperial line . Li Gang pressured Gaozong to execute Zhang for betraying the Song . The emperor relented and Zhang was coerced into suicide . The killing of Zhang showed that the Song was willing to provoke the Jin , and that the Jin had yet to solidify their control over the newly conquered territories . The submission and abolition of Chu meant that Kaifeng was now back under Song control . Zong Ze ( <unk> ; 1059 – 1128 ) , the Song general responsible for <unk> Kaifeng , <unk> Gaozong to move the court back to the city , but Gaozong refused and retreated south . The southward move marked the end of the Northern Song and the beginning of the Southern Song era of Chinese history . 
