 A notable betrayal did occur on the Song side , however : Wu Xi ( <unk> ; d . 1207 ) , the governor @-@ general of Sichuan , defected to the Jin in December 1206 . The Song had depended on Wu 's success in the west to divert Jin soldiers away from the eastern front . He had attacked Jin positions earlier in 1206 , but his army of about 50 @,@ 000 men had been repelled . Wu 's defection could have meant the loss of the entire western front of the war , but Song loyalists assassinated Wu on March 29 , 1207 , before Jin troops could take control of the surrendered territories . An Bing ( <unk> ; d . 1221 ) was given Wu Xi 's position , but the cohesion of Song forces in the west fell apart after Wu 's demise and commanders turned on each other in the ensuing infighting . 
