With the collapse of the Western Roman Empire in the latter fifth century A.D. the rule of empire vanished in northern Europe, and with it for a time an integrated market economy in the Mediterranean, North Africa, and Asia. The absence of the legions to provide security in the countryside against brigands and invaders at first led to ever greater disruption of farmland, while massive fortifications, not the courage of soldiers in open battle, were seen as the more reliable defense of the cities. The lack of central taxation meant that aqueducts, terraces, bridges, and irrigation canals were not properly maintained and often abandoned, leading not merely to the loss of potable water in the cities but also to a decline in agricultural productivity as valleys silted up and terraced land eroded.

The erosion of central imperial government and the collapse of urban culture also meant an end to large standing armies. Italy, Spain, Gaul, and Britain, in the absence of authority from Rome, were convulsed by a series of invasions and migrations by Vandals, Goths, Lombards, Huns, Franks, and Germans. Yet the victorious newcomers by the sixth and seventh centuries were no longer nomadic, but often had settled permanently in Roman territory, gradually converted to Christianity, learned some Latin, and carved out petty kingdoms guided loosely by the old Roman bureaucratic and legal tradition. If the new armies of western Europe were tiny and fragmented in comparison to Rome and often ensconced in fortified castles and towns, they nonetheless continued to rely on levies of heavy infantrymen fighting in columns, not tribal swarming, when it became necessary to engage in decisive battles.

The final collapse of Rome also brought a population decline in western Europe; and economic activity was lethargic for much of the so-called Dark Ages between 500 and 800. Christianity began to encroach on public and private lands, requiring enormous acreages to support monasteries, churches, and nunneries, whose clergy in the strict economic sense were not especially productive. If the estates of the old Roman patricians were sometimes unwisely expropriated for horse raising by the aristocracy of Franks and Lombards, then similarly the church also used the harvests from scarce and precious farmland to support a vast bureaucracy and an ambitious building program. By the end of the fifth century A.D., no single kingdom from Lombard Italy to Visigoth Spain could muster an army the size of the Roman force that had been annihilated at Cannae seven hundred years earlier.

Yet the fall of Rome often spread, rather than destroyed outright, classical civilization, as the fragments of empire slowly recovered and kept alive the cultural core of the old West. Writing continued. Even literature and scientific investigation were never completely lost. Latin remained the universal script of government, religion, and law from Italy to the North Sea. The Dark Ages (the term originally referred to the dearth of written knowledge that survived about the era) were characterized not so much by the chaos of an empire fallen as by the new diffusion of much of classical culture—language, architecture, military practices, religion, and economic expertise—into northern Europe, especially Germany, France, England, Ireland, and Scandinavia.

Islam had spread in the south and east by the creation of an entirely new theocratic state; in contrast, the remnants of classical culture, fused with Christianity, advanced throughout western and northern Europe due to the collapse of the Roman Empire. “Despite the resulting turmoil and destruction,” Henry Pirenne pointed out in regard to the supposed end of Roman civilization in northern Europe during the fifth century A.D., “no new principles made their appearance either in the economic or social order, nor in the linguistic situation, nor in the existing institutions. What civilization survived was Mediterranean” (Mohammed and Charlemagne, 284).

The sixth and seventh centuries actually saw improvements. Throughout the latter decades of the Roman Empire, there had been a gradual displacement of agrarians, concentrations of huge amounts of wealth, and constant class strife in the cities. The continuance of classical culture in ancient Gaul in the sixth through eight centuries, even under radically different and troubled material conditions, often meant that local government was more responsive to rural problems than had been Rome in its last two centuries. Under the Merovingians and Carolingians there nowhere reappeared the vast numbers of slaves that had characterized Roman civilization (by the fourth century A.D. in certain parts of the empire nearly a quarter of the population had been servile). Though Roman wealth and nationhood were gone for a time from the West, the deadly military tradition of classical antiquity was nevertheless kept alive. Most of the great military discoveries in both weaponry and tactics to come in the next millennium would originate in Europe—the continuing dividends of the Western approach to the dissemination of empirical data, the scientific method, and free inquiry.

“Greek fire” emerged at Byzantium somewhere around 675. Although the exact ingredients and their ratios of mixture remain unknown to this day, the torrent of flame that was shot out of Byzantine galleys was apparently a potent fusion of naphtha, sulfur, petroleum, and quicklime that could not be extinguished by water—a nearly unquenchable toxic spume that could incinerate enemy ships in seconds. Equally ingenious as the chemistry of Greek fire was its method of delivery, which involved a keen knowledge of pumps, pressurization, and mechanical engineering. A sealed container was heated from below with fuel and bellows and injected with forced air from a pump. Then the compressed mixture was forced out another outlet into a long bronze tube. The jellied mass was ignited at the end of the barrel, resulting in a sea of continuous flame spurting out from this ancient flamethrower. Ships with such fiery contraptions allowed the small Byzantine navy mastery of the eastern Mediterranean and saved Constantinople itself on occasion—none more dramatic than Leo III’s incineration of the Islamic armada of the caliph Sulaymān in 717 in waters surrounding the capital.

Controversy surrounds the exact origins of the stirrup—it may have been originally of Asian design—but by A.D. 1000 most Western cavalrymen were employing new saddles equipped with stirrups, even if they learned of their use via the Arabs, who had copied the original designs either from the Byzantines or by trading with the Orient in the early seventh century. Under the western European kingdoms, the stirrup was envisioned not merely as an aid to horse mastery but as integral to the emergence of a new lance-bearing knight, who could for the first time absorb the shock of spearing a fixed target on the gallop without being thrown from his mount. While such lancers could never break true infantry, small corps could easily ride down isolated groups of foot soldiers during both attack and retreat. The stirrup meant not that western European militaries were dominated by heavy lancers, but that their mostly infantry armies, at key moments in the battle—when gaps appeared in enemy lines or during the rout—could send out small corps of deadly horsemen to slaughter with impunity light infantrymen and poorly organized foot soldiers.

The crossbow—in use throughout Europe by 850—was a smaller-sized derivative of the classical “belly-bow,” through substitution of a handheld crank for large torsion cables and sprockets. Scholars cite the crossbow’s deficiencies in comparison with either the later English long-bow or the Eastern composite bow, both of which had greater range and rates of fire. The crossbow, however, required far less training to use than either, did not tire the archer to the same degree as hand-pulled bows, and its smaller all-metal bolts had greater penetrating power at short ranges. Crossbow bolts alone were able to slice through the heavy chain mail of the knight, and meant that a relatively poor man without much training could kill both an aristocratic horseman and his armored mount in seconds for the cost of a tiny metal projectile. Consequently, the church often issued edicts against its use—a doomed prospect of technological repression with no heritage in the West—and finally retreated to the position that crossbows should be outlawed in all intramural wars between Christians.

Siege engines underwent constant improvement. After 1180, vast catapults were powered by counterbalances rather than torsion alone. Such trebuchets often had ten-ton counterweights and could throw stones of three hundred pounds well over one hundred yards, exceeding the delivery weight of the old Roman traction catapults fivefold, while maintaining nearly the same range. In turn, fortifications were built entirely of stone and to heights unimagined by classical engineers, replete with intricate towers, crenellations, and interior keeps. It was not merely that European castles and walls were larger and stouter than those in Africa and the Near East, they were more numerous as well, due to improvements in the cutting, transportation, and lifting of stone. Plate armor, common by 1250, was also a European specialty, ensuring that most European knights and infantrymen were far better protected than their Islamic opponents. When gunpowder was introduced from the Chinese in the fourteenth century, Europe alone was able to craft dependable and heavy cannon—Constantinople fell in 1453 through the efforts of Western-fabricated artillery—and handheld matchlock weapons in any great number. So, too, fully rigged, multisailed ships were common in European waters by 1430, and were superior to any vessels in either the Ottoman or the Chinese navies.

Key to this continuing Western ability to craft good weapons, along with fluid and innovative tactical doctrine, was the embrace of published military research, which married theory with field experience to offer pragmatic advice to commanders in the field. The late Roman handbooks of Frontinus, and to a greater extent Vegetius, were copied even throughout the Dark Ages and became a bible of sorts to many western European warlords. Rabanus Maurus, the ninth-century archbishop of Mainz, published an annotated De re militari specifically to improve Frankish warfare. For the next four hundred years, adaptations and translations of Vegetius appeared throughout Europe by Alfonso X (1252–84), Bono Gimaboni (1250), and Jean de Meung (1284).

European siegecraft itself was unmatched, precisely because it followed in the past tradition of classical poliorkētika (the arts of “polis enclosing”). Manuals such as the Mappae Clavicula instructed besiegers in the use of engines and incendiary devices. The emperors Maurice (Ars militaris) and Leo VI (Tactica) outlined Byzantine infantry and naval tactics in preparing manuals for their generals and admirals to keep the Mediterranean Sea and its harbors free from Arab fleets. In contrast, Islamic writing on war was rarely abstract or theoretical—or even practical—but more holistic and philosophical, and largely concerned itself with the proper rules and conduct of the jihad.

Among the early Franks this need to write about war and to publish manuals about its practice were in direct emulation of Roman and Greek thinkers. Military practice did not operate in a vacuum, but was closely connected to the presence of an educated elite familiar with classical ideas of military organization and weaponry. Under the Carolingians, a systematic approach was undertaken to the preservation of classical manuscripts, along with efforts to assure education in the Greco-Roman tradition:

Though defined by religion, Europe was also a community of scholars who read and wrote the same Latin language and who rescued a great part of the legacy of antiquity from irretrievable loss. In the ninth and tenth centuries, schoolmasters devised a new curriculum of studies based in part on the classics that they had rediscovered. In doing so they laid the foundations of educational practices for centuries. (P. Riché, The Carolingians, 361)

In addition, the historiographic tradition of Greece and Rome continued in the Christian East and West, especially the Hellenic and Roman propensities of Herodotus, Thucydides, Livy, and Tacitus to see history largely as the story of war and politics. Thus, Gregory of Tours (534–94, History of the Franks), Procopius (born ca. 500, History of the Wars of Justinian), Isidore of Seville (History of the Goths, written 624), and Venerable Bede (672–735, Ecclesiastical History of England ) all provided anthropological detail about various tribes as part of larger exegeses of intercultural conquests and defeats. The works of hundreds of other lesser-known chroniclers and compilers circulated throughout Europe, the sheer number of titles unmatched by anything published elsewhere.

There were numerous early Islamic historians, many of whom were candid and remarkably critical, but few saw history as really existing before the era of the Prophet (thus the maxim “Islam cancels all that was before it”). And the parameters of inquiry were limited by the Koran, whose literary and historical primacy tolerated no competition from mere mortals. Contrary to classical historiography—there seems to be little evidence of any early Arabic translation of the major Greek historians— lapses in morality, not tactical blunders or structural flaws, were cited as reasons for Islamic defeats. After Poitiers, Arab chroniclers, as would be true of Ottoman observers in the aftermath of Lepanto, attributed the Muslim slaughter to their own wickedness and impiety that had brought on the wrath of Allah.

The horse-drawn, iron-tipped plow first emerged in Europe, allowing farmland to be broken up more quickly and deeply than with the old wooden blades drawn by oxen. The ability to farm more efficiently gave Westerners greater food and opportunity than their counterparts to the south and east. By the end of the twelfth century, windmills, which were unlike anything in the Near East or Asia, appeared in England and northern Europe. With a rotating horizontal axis and a system of gears, such machines could mill wheat at rates unimagined either in classical antiquity or the contemporary non-West. Improved water wheels—more than 5,000 in eleventh-century England alone—were used not only to grind grain but to manufacture paper, cloth, and metal. The result was that Western armies were able to campaign farther from home—both because they could take greater amounts of supplies with them and because farmers could go on campaigns for longer periods. Historians often remark on the unruliness of Crusader armies, constant bickering in command, horrendous camp conditions, and the occasional imbecility of their tactics, forgetting that the transportation and supply of thousands of soldiers to the other side of the Mediterranean was a feat of logistical genius unmatched by Islamic armies of the day.

Science and technology alone did not save the smaller and more fragmented western European armies from their adversaries. The classical traditions of infantry organization and landed musters were kept alive as well. Military command and discipline followed Roman tradition, and so naturally nomenclature remained Greek and Latin. Byzantine emperors, in the manner of Macedonian lords, addressed their soldiers as systratiōtai— “comrades-in-arms.” Generals, as in classical Greece, remained stratēgoiand soldiers stratiōtai, while in the West free soldiers were milites, both pedites (foot soldiers) and equites (knights). Citizens continued to be recruited under legal and published codes of conduct—the so-called “capitularies”—with explicit rights and responsibilities.

Charles Martel’s army was not as disciplined or as large as a Roman consular army, but the manner in which its heavily armed spearmen and swordsmen were mustered, attacked on foot, and kept in rank was consistent with the classical tradition. Campaigns required the approval of assemblies, and rulers were subject to audit after battle.

By the end of the eighth century two seemingly insurmountable obstacles that had once weakened the old Roman imperial levies of the fifth and sixth centuries A.D.—the failure of Roman citizens to serve in their own armies, and the religious strictures against civic militarism and wars of conquest by the early Christian church—were beginning to erode. Augustine had composed his City of God after the sack of Rome in A.D. 410 to associate divine punishment with the sins of Romans. Even earlier, a few Christian emperors, like Gratian, had dismantled public statues and commemoration of military victory as somehow antithetical to Christ’s message of peace and forgiveness. Yet by early medieval times the earlier pacifism of the Roman church fathers like Tertullian (Ad martyres, De corona militis), Origen (Exhortatio ad martyrium, De Principiis), and Lactantius (De mortibus persecutorum) was often ignored, as the creed of the Old Testament and its idea of wars against the unbelievers regained primacy over the message of the Gospels. Thomas Aquinas, for example, could outline the conditions of “just” Christian wars, in which the cause of the conflict could make war a moral Christian enterprise. Christianity would never exhibit the martial fervor of Islam, but during the Dark Ages it more or less curbed its early pacifist pretenses and its distance from the affairs of worldly politicians. The military of Joshua and Samson, not the loving remonstrations of Jesus, was invoked to keep Islam at bay.

Franks, Lombards, Goths, and Vandals may have been tribal, and their armies were poorly organized; yet such “barbarians” nevertheless shared a general idea that as freemen of their community they were obligated to fight—and free to profit from the booty of their enemies. In that sense of civic militarism, they were more reminiscent of the old classical armies of a republican past than had been the hired imperial legionaries on Rome’s defensive frontier:

The massive reliance on citizen-soldiers in the West lowered the demands on the central government for expenditures to support the military. . . . Indeed, the flexibility of the West in building on developments that took place during the later Roman Empire resulted in immense military strengths, which, for example, proved their worth in the success for two centuries of the crusader states against overwhelming odds. (B. Bachrach, “Early Medieval Europe,” in K. Raaflaub and N. Rosenstein, eds., War and Society in the Ancient and Medieval Worlds, 294)

The legions had crumbled not because of organizational weaknesses, technological backwardness, or even problems of command and discipline, but because of the dearth of free citizens who were willing to fight for their own freedom and the values of their civilization. Such spirited warriors the barbarians had, and when they absorbed the blueprint of Roman militarism, a number of effective local Western armies arose—as the Muslims learned at Poitiers.