China's expansion to the south in the imperial period has generally produced uncomplicated stories. Han migrants seeking opportunities beyond the central plains spread to the frontier through successive waves of migration and cultivated roots in the hostile but sparsely inhabited country. They transformed the landscape of the border zone with their agricultural tools and techniques, introduced to the territory their social and economic institutions, and disseminated throughout the region the beliefs and practices of Chinese culture. In their new surrounding, settlers found opportunities not only in farming but also in hunting, fishing, gathering, logging, mining, and trading. Many who migrated to the south did so to escape wars or natural calamities, but others were soldiers sent by Chinese rulers to establish control. Han settlement was almost always accompanied by the extension of the Chinese state: civil administration was organized in areas where the fiscal base was considered sufficiently stable, and garrisons were set up at strategic locations where military presence was deemed essential. China's “march toward the tropics” – as Herold Wiens suggestively titled his now-classic study published over half a century ago – has thus been regarded by many as a process of colonization, sustained by the economic needs of Han settlers, the political interests of the state, and the “urge to civilize” of Chinese rulers and elites.