What knowledge of Dunhuang do we have before the introduction of Buddhism? Crossroads of trade routes, Dunhuang and its environs is a territory that is paradoxically fairly poorly known in the period preceding the manuscripts of Mogao. At the turn of the second and first centuries BCE, the area of Dunhuang is occupied by the Xiongnu armies, then conquered and occupied by the military forces of the Western Hans. In the span of twenty years, this same area becomes the western border with the Chinese Empire as well as the doorway to the western lands. In parallel, such an important route is equipped with defenses against the threats of the populations repelled from this same area. The local geography is completely reorganized and Dunhuang becomes an imperial prefecture with its districts. In a few years, important migrations of populations from the center of the Empire come and colonize this new administrative region: new sectors, until then marshy, become irrigated villages. Dunhuang becomes an important town as well as a military outpost for the western regions and its “limes” constitutes the western border of the Han Empire. This development takes place in the span of a few dozens of years. This communication will present new aspects of the Imperial prefecture of Dunhuang under the Western Han relying on historical, epigraphic and archeological unpublished data.