Yelü Bei subsequently served as Emperor Taizu's forward commander in campaigns against the Wugu () and the Tangut tribes. Later, on incursions that Emperor Taizu made into the Chinese/Shatuo state Former Jin territory — specifically, Jin's Lulong Circuit (盧龍, headquartered in modern Beijing) — he left Yelü Bei in charge at his capital Linhuang Municipality (臨潢, in modern Chifeng, Inner Mongolia). It was during this time that Yelü Bei was said to have drafted a plan to conquer Khitan's eastern neighbor Balhae.