The relationship between climate change and wars waged between nomadic and farming groups from the Western Han Dynasty to the Tang Dynasty period

Abstract. In ancient China, shifts in regional productivity of agriculture and animal husbandry, caused by climate change, either led to wars or peaceful relations between nomadic and farming groups. During the period spanning the Western Han Dynasty to the Tang Dynasty, 367 wars were waged between these groups. While 69 % of the wars were initiated by nomads, 62.4 % were won by the farming groups. On a centennial timescale, the battlegrounds were mostly in northern areas (at an average latitude of 38.92° N) during warm periods, moving southward (at an average latitude of 34.66° N) during cold periods. On a decadal timescale, warm climates corresponded to a high incidence of wars (a correlation coefficient of 0.293). While farming groups were inclined to initiate wars during dry and cold periods, their chances of achieving victory were reduced at such times. The main reasons for this are, first, that a warm climate provided a solid material foundation for nomadic and farming groups, contributing especially to enhanced productivity among the former. However, the overriding desire of nomadic groups to expand essential subsistence means led to wars. Second, during cold periods, farming groups moved to and settled in the south, while nomadic groups occupied the Central Plain. Thus, the locations of the battlefields also changed. While other factors also influenced these wars, climate change served as a backdrop, playing an indirect role in wars between these groups.