The Jurchens get into a conflict with the Mongols or the Khitai, with the Eastern Turks and conquer Mongolia first, then start moving west, including conquering Hsi Hsia and Kara Khitai and Tibet before taking on Song China. The Jurchen realize that they need to unify all of the steppe peoples (and the Siberian forest too, if possible, or they will not have the numbers to conquer China. If the Jurched arrive in Europe in the 8th Century having built the kind of institutions that will hold an empire together, they stand an excellent chance of conquering most or all of continental Europe since the nations of Europe have not completely gelled yet. After unifying the steppe and Europe, the Jurched may be able to take on China and conquer the Song completely. And hopefully, they do not have the problem with alcohol that the Mongols appear to have. IOTL.