Destructive Creation? The Incredible Shrinking Byzantine and Tang Empires

Leonard Dudley, Université de Montréal

Consider the Mosque-Cathedral in Cordoba and the Tianning Temple in Beijing, each constructed between the tenth and twelfth centuries by an invading culture. These structures symbolize the unprecedented contractions of the Byzantine and Tang empires between the seventh and the ninth centuries. In each case, a region that had maintained its territorial integrity for many centuries was successfully invaded by a foreign cultural group – the Umayyad Caliphate in the west and the Kuchans in the east. The principal previous explanations are: (1) cultural determinism (2) technological determinism; (3) climate change. Each offers elements of a possible explanation; however, something important is missing. Why had such changes not occurred before? Why did they occur almost simultaneously at opposite ends of the Eurasian landmass? Why were their effects so long-lasting? The answer proposed here is recombinant innovation: that is, relatively short intervals in which evolving information technology combined suddenly with parallel evolution in tools technology. This paper argues that (1) there are heavy fixed costs to maintaining an empire; (2) a shock that lowers these fixed costs will tend to reduce the empire’s equilibrium territory; (3) such a shock will also increase the equilibrium rate of taxation. Consider the following evidence. From the seventh to ninth centuries, the diffusion of the Aramean consonantal alphabet and heavy cavalry technology provided the pastoral cultures of Arabia and central Asia with unprecedented organizational capability and mobility. Consequently, the large infantry armies controlled by stationary bureaucracies that constituted the basic defensive force of agricultural societies were no longer able to compete. When dry, cool weather struck the pastoral homelands of Asia, the inhabitants invaded the agricultural regions of northern China and the Mediterranean basin. By the mid-tenth century, there were multiple quasi-feudal states in regions previously controlled by the Tang and Byzantine empires.

No extended abstract or paper available

 Presented in Session 24. Empire and Its Perils