Technology and complexities of the Inner Asian frontier reflected in crossbow bolts

The Inner Asian frontier along the Gobi Desert was an arena for competition between the Xiongnu (ca. 209 BCE-100/150 CE) and Han (206 BCE-220 CE) empires. A number of crossbow bolts from two military outposts there were examined to infer technological and political environments of this region. The analytical results reveal evidence of an established bolt-manufacturing technology based on the Cu-Sn-Pb system typical of the Han dynasty. It was also found that alloys within a specific composition range were most frequently selected as a preferred material. In many cases, however, the tin and lead contents were significantly away from this standard formula. Moreover, the dependency on non-standard methods showed notable variation between the outposts under consideration. The above results demonstrate that these sites shared in a common tradition based on a Han dynasty standardized model, but differed significantly in the implementation of these standards. The non-standard technologies likely represented manufacturing away from well-supplied production centers and reflected shifting frontier environments that often imposed restrictions on transport, communications, and access to material or technological resources. The occurrence of such alloys, therefore, may be indicative of the nature of supporting systems available to these peripheral sites. This observation suggests that crossbow bolts might serve as a medium for clarifying complex and dynamic border situations in terms of supply chains, interaction networks, and political affiliations.