The appropriation of resources beyond the borders often took the form of asymmetric exchange. Craft goods were regularly traded in the frontier for exotic and valuable raw materials (Cooter 1977; Paynter 1985; Waller- stein 1976). These activities often occurred in frontier trading depots, and beyond, in advance posts (Algaze 1993; Gorenstein 1985; Gorenstein and Perlstein 1983; Redmond 1983). In the New World, the Zapotecs, in the Cuicuitlan Canada, instituted neutral ports of trade to channel valuable materials after blocking existing commercial routes (Redmond 1983). Likewise, in the frontier region of Acambaro between the Tarascan and Aztec states, the military installations also served as nodes of exchange and diplomatic negotiation (Gorenstein 1985:104).
Ancient frontiers also witnessed the formation of prestige-good economies, and competing elite segments used imperial goods to display emergent social affiliations and political allegiances (Kristiansen 1991). This in turn promoted sharp status differentiation and competition (Helms 1992; Kristiansen 1991; Schortman and Urban 1987). This was the case of the steppe Mongols of the thirteenth century, who recurrently formed alliances with—or against—the Chinese empire to force more favorable trading conditions. These coalitions disintegrated and reorganized periodically, and raids against the Chinese frontier often correlated with changing trading circumstances (Barfield 2001; Hall 1991).