 The western army , led by Wanyan Zonghan , departed from <unk> and headed towards Taiyuan through the mountains of Shanxi , on its way to the Song western capital Luoyang . The Song forces were not expecting an invasion and were caught off guard . The Chinese general Tong Guan was informed of the military expedition by an envoy he had sent to the Jin to obtain the <unk> of two prefectures . The returning envoy reported that the Jurchens were willing to <unk> an invasion if the Song ceded control of Hebei and Shanxi to the Jin . Tong Guan retreated from Taiyuan and left command of his troops to Wang Bing . Jin armies besieged the city in mid January 1126 . Under Wang Bing 's command , Taiyuan held on long enough to stop the Jurchen troops from advancing to Luoyang . 
