The Restrictive Imperial Frontier
Restrictive imperial frontiers often acted as strategic military barriers and socioeconomic filters, where control was achieved by a careful balance between coercion and diplomacy. Selectively located at important nodes of communication, transportation, and trade, these militarized perimeter segments served as effective filters to control trade and the transit of people across borders (Anderson 1996; Martinez 1994; Parker 2002). Frequently, these frontiers took the form of military sections on the weakest flanks or in areas of economic importance. This defensive strategy might have been supplemented by advanced military outposts and mobile troops beyond the fortified segments. Therefore, restrictive frontiers were likely to be established along important economic and ecological interfaces and in valuable exchange network areas that ancient empires intended to control. Archaeologically, these defensive shields were manifested in the construction of strings of fortresses built and manned by the state forces in vulnerable passes, in economically valuable zones, or at important road intersections. Because this strategy entailed the use of force to control frontier surplus extraction and trade, social relations with native transborder groups were not a dominant feature. Rather, their participation was limited.