State Agriculture on the Ecological Margins of Empire: Military Colonies and Environmental Adaptation in the Sui–Tang Period (6th–8th Centuries CE)

Throughout the first millennium of East Asian imperial history, Chinese empires periodically extended military control over the semi-arid to arid southern Central and Inner Asia. During warmer, wetter climatic phases, states undertook efforts to establish or restore agricultural settlements in the region. Crop production was primarily intended to sustain frontier garrisons and their livestock through systems of state-organized military colonies (tuntian), in which soldier-farmers cultivated the land. The military colonies addressed growing demand for land and agricultural output to support both people and livestock. Recent scholarship on Han military farming (Trombert 2020) argues that agricultural colonies in the Hexi Corridor and Tarim Basin were largely unproductive and placed heavy demands on soldier-farmers, who had to balance cultivation with military service; the main significance of military colonies was likely not in their productivity, but rather in their role as strategic footholds that facilitated subsequent civilian settlement. Building on this argument, I examine the Tang military colonies along the Yellow River in the northwestern fringes of the empire, from the Qinghai Plateau to the Ordos Loop. This semi-arid region, situated at the edge of the monsoon zone, was traditionally more conducive to an agropastoral economy. It comprised the southern segment of the trade routes connecting Central Asia, extending through the Hexi Corridor. The Tang established large, permanent armies in the region and expanded agricultural settlements to sustain them. Scholars argue that the expansion of cropland into typically unsuitable areas was likely enabled by a particularly favorable climatic period in the 7^th century, characterized by warm and humid conditions. Rising temperatures could have enabled earlier planting dates and extended growing seasons, while also expanding arable land into higher-altitude regions. Increased precipitation would have further supported crop growth by boosting water availability. Unlike earlier periods, Tang administrative records detail the civil and military populations, livestock numbers, farm counts, crop types, and the man-days of labor needed to cultivate each crop. This extensive data can serve as a proxy for productivity and sustainability. By combining historical and administrative data with climatic data, the paper emphasizes the importance of studying how state institutions addressed environmental challenges and climate variability in the empire's semi-arid peripheries. It shows how military farms relied on continuous state intervention, particularly in land distribution, irrigation system maintenance, and labor enforcement.