In 926, Emperor Taizu decided to conquer Balhae. In a campaign, he captured the important Balhae city Fuyu (夫餘, in modern Siping, Jilin). (This appeared to have ended the Balhae state, even though Emperor Taizu did not at this time capture Balhae's capital Longquan.) Emperor Taizu set up a Dongdan Kingdom over the old Balhae territory, with its capital at Fuyu, and made Yelü Deguang's older brother Yelü Bei its king, with the title of "Imperial King of Man" (人皇王, "Ren Huangwang"), echoing the titles used by himself ("Imperial Emperor of Heaven," 天皇帝, "Tian Huangdi") and his wife (Yelü Bei's mother) Empress Shulü ("Imperial Empress of Earth," 地皇后, "Di Huanghou"). He gave Yelü Deguang the title of "Generalissimo Crown Prince" and made Yelü Deguang in charge of the Khitan capital Linhuang (臨潢, in modern Chifeng, Inner Mongolia), which Yelü Bei had previously been in charge of.