INTRODUCTION The purpose of this book is to provide a systematic commentary on the records about the Western Regions preserved in the “Xiyu zhuan 西域傳” (Monograph on the Western Regions) in the official histories of the Western and Eastern Han 漢, Wei 魏, Jin 晉, Southern and Northern dynasties. The “Xiyu zhuan 西域傳” (Monograph on the Western Regions) in the official histories of the Western and Eastern Han 漢, Wei 魏, Jin 晉, Southern and Northern dynasties, collectively constituting a complete system, are important primary sources for studies on Central Asia, South Asia, Western Asia, and even Europe and North Africa prior to the seventh century CE and are specially valued by scholars in China and elsewhere. Since the annotations by Ding Qian 丁謙 [1843-1919] toward the end of the Qing 清 dynasty, there have been no attempts to interpret this body of materials in a systematic manner, except for some works on individual pieces. Today, when great progress has been made in the historical study of the area, particularly Central Asia, a new annotated edition of this body of literature with a commentary should be on our agenda. There are fifteen official histories for the period the Western and Eastern Han 漢, Wei 魏, Jin 晉, Southern and Northern dynasties, eleven of which include the “Xiyu zhuan 西域傳” (Monograph on the Western Regions); namely, the “Dayuan liezhuan 大宛列傳” (Monograph on Dayuan) of Shiji 史記 (ch. 123), the “Xiyu zhuan 西域傳” (Monograph on the Western Regions) of Hanshu 漢書 (ch. 96), the “Xiyu zhuan 西域傳” (Monograph on the Western Regions) of Houhanshu 後漢書 (ch. 88), the “Xirong zhuan 西戎傳” (Monograph on the Western Rong ) of Jinshu 晉書 (ch. 97), the “Xibei zhurong zhuan 西北諸戎傳” (Monograph on the Various Rong 戎 of the Northwest) in Liangshu 梁書 (ch. 54), the “Xiyu zhuan 西域傳” (Monograph on the Western Regions) of Weishu 魏書 (ch. 102), the “Yiyu zhuan 異域傳 B” (Monograph on Foreign Lands) of Zhoushu 周書 (ch. 50), the “Xiyu zhuan 西域傳” (Monograph on the Western Regions) of Suishu 隋書 (ch. 83), the “Xiyu zhuguo zhuan 西域諸國傳” (Monograph on the Various States in the Western Regions) of Nanshi 南史 (ch. 79), the “Xiyu zhuan 西域傳” (Monograph on the Western Regions) of Beishi 北史 (ch. 97), and the “Xirong zhuan 西戎傳” (Monograph on the Western Rong) chapter of Weilüe 魏略 as quoted in Sanguozhi 三國志 (ch. 30) annotated by Pei Songzhi 裴松之. Specifically, it can be noted.