Shortly after conquering Fuyu, however, Emperor Taizu fell ill and died while still at Fuyu. Empress Shulü took over effective leadership of the Khitan, and she and Yelü Bei began the trek of escorting Emperor Taizu's casket back to Linhuang, leaving one of Emperor Taizu's younger brother Yelü Anduan (耶律安端) temporarily in charge at Dongdan. Once then returned to Linhuang, she wanted to divert the succession away from Yelü Bei, as she had favored Yelü Deguang. However, formally, she called an assembly of the chieftains, along with Yelü Bei and Yelü Deguang, and stated to them, "I love both of my sons, and I do not know which one to make emperor. You can decide which one you wish to support by holding his rein." The chieftains, knowing that she favored Yelü Deguang, rushed to him and held to his rein. She thereafter declared him emperor (as Emperor Taizong). Yelü Bei, angry over this turn of events, took several hundred soldiers and wanted to flee to Later Tang (Jin's successor state), but was intercepted by Khitan border guards. Empress Shulü did not punish him, but sent him to Dongdan.