 The Jin were weakened by the pressure of the rising Mongols to the north , a series of floods culminating in a Yellow River flood in 1194 that devastated Hebei and Shandong in northern China , and the droughts and swarming locusts that plagued the south near the Huai . The Song were informed of the Jurchen predicament by their ambassadors , who traveled twice a year to the Jin capital , and started provoking their northern neighbor . The hostilities were instigated by chancellor Han Tuozhou . The Song Emperor <unk> ( r . 1194 – 1224 ) took little interest in the war effort . Under Han Tuozhou 's supervision , preparations for the war proceeded gradually and cautiously . The court venerated the <unk> hero Yue Fei and Han orchestrated the publishing of historical records that justified war with the Jin . From 1204 onwards , Song armed groups raided Jin settlements . Han Tuozhou was designated the head of national security in 1205 . The Song funded insurgents in the north that professed loyalist sympathies . These early clashes continued to escalate , partly <unk> by <unk> Song officials , and war against the Jin was officially declared on June 14 , 1206 . The document that announced the war claimed the Jin lost the Mandate of Heaven , a sign that they were unfit to rule , and called for an insurrection of Han Chinese against the Jin state . 
