We have called this section “The Age of Migration and Invasion,” and the impact of nomads of various types is one of the key themes in this period. The end of the classical world witnessed significant movements of peoples across Eurasia and considerable flux in the boundaries and cultural content of the major civilized traditions. The instability of the age was one factor in the rise of the salvation religions, and the link between war and religion is the second major theme of this period. Both the impact of nomads and the rise of holy war highlight a central focus of this book as a whole: that warfare is one expression of the societies that wage it, an expression dominated in this age by landed warrior elites.
Horse-archers from the Asian steppes were the dominant nomadic military force at this time, but not the only one. Most of the seminomadic Germanic tribes facing the Roman Empire moved largely on foot, and their movements constituted migrations more than the rapid invasions and withdrawals of the horse peoples. Some, such as the Saxons, also moved by sea, putting them in the second major category of nomadic raiders, the sea peoples, of whom the Vikings are the most famous. The tribesmen of the Saudi Arabian peninsula constitute a special subclass of nomadic horse people. Their tactical traditions, having little emphasis on archery, differed from those of the steppe tribes. Their seventh-century explosion was unique in their history, in contrast to the steady waves of invasion and withdrawal on the steppes, as their homeland was too poor in resources to support the political hierarchies that powered the excursions of the Central Asian horsemen. But they shared many of the advantages, at least briefly, of nomads everywhere.
Mobility, strategic and tactical, was the military key to the success of all types of nomads. Horses or ships, tied to no particular base of operations, let nomadic forces strike from unexpected directions and at unexpected times, making planned responses to their raids difficult. To this advantage, the horsemen of the steppes added accurate firepower on a large scale from their composite bows and their unmatched soldierly skills bred from their lifestyle—the skills honed in constant competition with other nomadic groups, and the hardness that led them to hold settled peoples in contempt as “soft” and “effeminate.” Used to a life on horseback with short rations, the horsemen added a ruthlessness such that massed infantry were viewed as just another slaughterable herd animal. Such conditions also trained effective leaders; unity among nomads was the major limitation on their offensive actions. Sea peoples were less formidable tactically, but fighting them was expensive. Only Byzantium and Song China, big empires with vital maritime interests, could afford the permanent combat navies that could check raiders at sea. Local responses tended toward systems of fortification that were only marginally effective.
The impact of nomadic invasions was felt throughout the Eurasian world in this period, from Rome to China—in the Arab regions, in Byzantium, in India, and again near the end of the period in southwest Asia. Nomadic activity and the movement of peoples created some links and cross-cultural fertilization, especially if the creation of the vast Islamic world is interpreted as resulting from an originally nomadic impulse. The trade networks that spread from the Straits of Gibraltar to the Straits of Malacca tied together a truly world civilization. But, in most cases, the migrations and invasions of 400-1100 probably disrupted existing patterns and links more than they added to them. The early waves certainly coincided with the breakdown of classical empires at both ends of the Silk Road and with the temporary decline of the road itself, and they advanced the political fragmentation that succeeded the Age of Empires everywhere. Nomadic horsemen thus contributed to an increase in the importance of cavalry in the warfare of this age both directly by their tactics and indirectly through the decline of the central authorities necessary to create effective infantry in settled polities.
Horse-archers had appeared on the scene early in the classical age, but their impact increased noticeably after 400. Why? Technological explanations based on the introduction and spread of the stirrup tend to bog down in the details of archaeological dating. The stirrup may have played a role in slowly increasing the military efficiency of nomadic horsemen, but it was not crucial to their increased impact after 400. Instead, larger social and economic trends stand out. Most important, the various civilizations surrounding the steppes had grown in size and wealth over the prior millennium. Not only did their greater wealth make them more attractive targets for nomadic raiders, but the export of some of that wealth to nomadic tribes in the form of trade and tribute stimulated and made possible the formation of the nomadic hierarchies and state structures that were a prerequisite to successful nomadic invasions. The geographic spread of areas under settled control put pressure on nomadic territories while at the same time making routes into settled lands more accessible. Such geographic expansion could also set up a domino effect, as, for example, when the Han expansion in the first century BCE contributed to the westward movement of tribes that eventually put pressure on Rome. Nomad populations, too, though more constrained by the economic limits of their homelands, had grown, as had the size of their herds. The combination of greater inputs of goods from settled areas and larger nomadic tribes resulted in larger confederations of Asiatic tribes that posed a greater threat to their neighbors. Whether the subsequent increase in nomadic activity was a cause or a result of the decline of the big classical empires (probably a combination of both), it certainly contributed to the disorders of the postclassical world. In the specific case of the Arab explosion, the exhaustion of the Byzantine and Persian empires after decades of war opened the door to Arab conquests, while the historically unusual unity of the Arabs flowed in small part from local economics and in large part from the leadership of Muhammad and his successors. The latter links the nomadic impact to the rise of the great salvation religions and their relationship to war.
The rise of the great salvation religions—Buddhism, Christianity, and Islam (and perhaps parts of Hinduism)—was not fundamentally a military phenomenon, even in the case of Islam, whose early expansion was so closely tied to conquest. The religions responded to spiritual and political needs raised by the conditions of the classical and postclassical ages, meeting those needs across a broad spectrum of society. Indeed, all of them tended toward a democratization of classical cultures, helping create more peasant-friendly systems of belief in response to troubled times.
Inevitably, however, religion and war, two activities that along with agriculture dominated life in the traditional world, became intimately linked. The link was often forged early on: The rise of Buddhism and Christianity as mass religions is associated with the careers of converted conquerors, Asoka and Constantine, and Islam’s founder, Muhammad, also acted as early Islam’s military leader. And with Christianity and Islam, the link developed into forms and theories of holy war, warfare conducted on behalf of religion and rewarded by the religion’s god. Jihad motivated the early Arab explosion; militant religion proved a powerful weapon in the expansion of western Christianity into pagan lands and in the defense of eastern Christianity against pagans, Persians, and Muslims. “Holy war” cultures rose from a number of causes. The intolerance of the monotheistic religions meant that they could accommodate force (with more or less comfort) as a tool of converting or punishing unbelievers. The wide class appeal of the religions also meant that they could mobilize popular commitment, and so contributed to a deeper rootedness of the various civilized traditions that sometimes brought them into more lasting conflict. And the prospect of martyrdom and salvation tied the ultimate reward promised by these religions directly to heroic military effort. The end result of this link was the creation of an ideological dimension to war that had not existed before and that tended to emphasize the differences rather than the similarities between competing traditions.
One job of the world historian, military or otherwise, is to recognize but see past differences to the underlying similarities and comparisons. It is true that different peoples have fought in different ways throughout history. In this period, nomads differed from settled peoples in styles of warfare; and, among the settled civilizations, there were a wide variety of tactical traditions and strategic patterns influenced by varying social, economic, religious, and cultural contexts. But fundamental economic constraints also imposed an underlying similarity on many of Eurasia’s peoples in terms of social and therefore military organization, a similarity that stands out with particular clarity in this age.
All traditional, or preindustrial, civilizations drew the vast majority of their wealth from agriculture, making land (and control of land) the key to power and prestige. In this period, with the decline or contraction in many areas of the centralized monetary and administrative systems of the great classical empires, control of landed estates became even more directly a source of power as well as economic support. This was even more true where contractions or disruptions in trade damaged the economies of cities. Even temporary declines opened the door to a greater role for rural elites with lordship of some sort over peasantry. The need to protect their source of wealth, especially in the absence of a strong central authority, led such men naturally to the role of warrior strongman, while considerations of prestige and strategic mobility usually led them onto horseback wherever horses could be raised, though how they fought (mounted or on foot, with missile weapons or hand-to-hand) could vary widely.
This widespread tendency to the domination of society by a mounted, rural warrior elite manifested itself in a number of ways throughout Eurasia. In less centralized polities, arrangements for the landed support of warriors were formalized in one way or another, becoming central to the sociopolitical organization of such areas. The emergence of feudalism in western Europe, of the iqta , in Islamic lands (especially under the Seljuk Turks), and of similar institutions in India exemplify this process. In areas that retained or recovered traditions of central control, accommodating the role and power of rural warrior elites proved a lasting challenge, for their very military usefulness made them a potential threat to state power. The Tang dynasty tried several ways to incorporate effective cavalry forces in their armies, and it was the dynasty most dominated by great warrior aristocrats. The Byzantine government’s Farmer’s Law institutionalized central protection of small farmers against the depredations of great landowners; when that balance broke down, the empire’s defenses collapsed.
In military terms, the same factors that heightened the role of mounted rural warriors—weakened central authority and urban economies in decline or disruption— also made the creation of effective infantry forces more difficult. Thus, after the emphasis in the classical age on the emergence of trained massed infantry forces, this age appears, in contrast, to be an age of cavalry. The effectiveness of nomadic horsemen adds to this impression, and, in some cases, nomadic cavalry were the rural warrior elites of various civilizations: The Tang and many Islamic states drew heavily on the military skills of their nomadic neighbors and rewarded them with land.
Against this fundamental background, we may now turn to the developments of the next age of world history, developments that would affect social, economic, and political structures and, in turn, the military systems linked to them.