The book is a representative monograph on the history, ethnic relations and foreign relations of medieval China. It focuses on the complex relations between Tang, Tubo and Dashi in the 7th and 8th centuries. The author examines a variety of first-hand materials, including the Chinese and Tibetan documents discovered in Dunhuang and Turpan as well as a substantial quantity of historical materials written in Arabic before reaching convincing conclusions that would help to advance academic research in related fields.