Scholars have long debated the extent to which political and demographic change from the mid-fourth to the early seventh centuries affected the exchange of goods within the borders of what was or had been the Roman empire, and between those in it and those situated on its shrinking borders. Clearly, Rome's vibrant long-distance trade with Han China and parts of the Indian Ocean had long since withered. Nonetheless, in the East the emerging Byzantine empire, with its sustained imperial leadership and bureaucracy, coinage, urban life, military viability, and naval control of the eastern Mediterranean basin retained its economic vitality while the West receded.
The relative poverty in the West and that of its Celtic, African, Germanic, and Scandinavian neighbors meant that much was lost when the money economy, viable and secure roadways, and safe coastal seaways disappeared as Germanic tribes and then kingdoms replaced the relatively unified and effective Roman state. Wealth had been flowing eastward since the early fourth century, with the flow turning to a flood as Germanic tribes moved through Gaul, northern Italy, and Spain at will. New and unstable coinages served local needs, but found little acceptance elsewhere. Piracy at sea, brigandage on land, and urban decay discouraged both movement of goods and the accumulation of wealth. Rome itself shrank to perhaps 5 percent of its highest population level, after having been sacked in 410 by Goths and again in 455 by Vandals. Disease took its toll on the population, too, in both the East and West, killing buyer and supplier alike (Cantor, pp. 384).
By the seventh and eighth centuries, large-scale migrations in the West had ended; tribal kingdoms of Lombards, Franks, Burgundians, and Anglo-Saxons had organized rudimentary territorial governments. Kings, nobles, and higher Christian clergy demanded and obtained some measures of luxury goods, but trade had hardly revived: the vast majority of people produced what they needed and exchanged locally for what they could not. Town life had not died out, especially in southern Gaul and Italy, but neither had it become a force in the economy of any Western region.
During the same period, the Muslim world emerged and raced across the former Persian empire and much of the Byzantine. While this erased many of the barriers to trade within the area now to be deemed Islamic, it erected barriers between the Byzantine world in the East and its former territories and lands beyond. Arab pirates preyed on Byzantine and what Western shipping still remained. Constantinople became the true metropolis of eastern Christendom, and both the major supplier and market for goods of all sorts. Its wealthy and lavish imperial court supported manufacturers of luxury goods in the city and scattered throughout the empire and imported goods when practicable.
Muslim capitals at Damascus and Baghdad, and later Cordoba and Cairo, did likewise. Placed as they were along major trade routes from Africa, the Indian Ocean and further east, Muslim merchants outstripped their Christian counterparts in variety, quantity, and quality of merchandise handled. Through trade, ...