A History of Warfare

John Keegan, a faculty member at the Royal Military Academy Sandhurst, Britain's cadet college, opens with a personal reflection on how a childhood illness left him with a permanent physical disability that disqualified him from military service, yet fate placed him among professional warriors for most of his adult life. From his years at Sandhurst he came to recognize that soldiers inhabit a world apart, bound by tribal regimental loyalties and a warrior culture that exists parallel to civilian society. This observation leads to the book's central argument: War is not, as the Prussian military theorist Carl von Clausewitz maintained in On War, merely a continuation of political intercourse by other means. War is always an expression of culture, often a determinant of cultural forms, and in some societies the culture itself.

Keegan challenges Clausewitz's dictum by pointing out that it presupposes the existence of states, rational calculation, and diplomacy, whereas warfare is far older than any of these institutions, reaching into primal human instincts of pride, emotion, and the urge to kill. He traces Clausewitz's biography to show how the Prussian officer's regimental upbringing, his experience of Napoleon Bonaparte's revolutionary armies, and his immersion in German idealist philosophy produced a theory that, while describing European state warfare with some accuracy, ignored the endemic warfare of pre-state peoples entirely. Keegan draws a parallel between Clausewitz and the German political theorist Karl Marx: Both used reductive logic to construct theories that purported to be scientific but were ideological, and both bore responsibility for catastrophic consequences when their ideas were taken to extremes.

To demonstrate that war is culturally rather than politically determined, Keegan presents four non-Western case studies. On Easter Island, a Polynesian theocracy regulated by mana (priestly authority) and taboo (sacred rights) degenerated into endemic warfare as population growth exhausted the island's resources, proving that war could terminate politics and culture rather than serve them. In early nineteenth-century southern Africa, the Zulu chief Shaka transformed a pastoral people into a militarized state with permanent age-regiments and close-order encirclement tactics, devastating communities across a vast region, yet the Zulus' rigid adherence to their methods led to destruction by British firepower in 1879. In the Islamic world, the prohibition against Muslim fighting Muslim produced the Mameluke institution, a system of military slavery in which Turkish youths were trained in mounted combat and formed into an elite warrior caste whose rejection of firearms led to their defeat by Ottoman gunpowder armies. In Japan, the samurai first adopted and then systematically eliminated firearms under the Tokugawa shogunate, the country's military ruling government, demonstrating that a warrior culture could resist technological change for centuries.

Keegan examines the deeper origins of warfare by surveying the debate over whether human aggression is innate or culturally produced and presenting four ethnographic case studies. The Yanomamö of the Orinoco basin escalate violence through graded stages from ritual duels to lethal raids, showing that even fierce peoples limit combat through graduated escalation. The Maring of highland New Guinea fight ritualized battles timed to 10-year pig-fattening cycles. The Maoris of New Zealand practice revenge warfare constrained by hilltop fortifications. The Aztecs of central Mexico wage ritual wars designed to capture sacrificial victims rather than conquer territory. From these studies Keegan draws the lesson that primitive warfare, for all its violence, was circumscribed by ritual and convention in ways that later warfare was not.

He traces the transition from constrained violence to organized warmaking through the development of agriculture and the rise of the first civilizations in Mesopotamia. There, the world's first cities, writing, and organized warfare emerged together, and by about 2340 BC, Sargon, the ruler of Agade, had founded the first empire, establishing the pattern of bureaucratic military organization that later empires would follow.

The book's middle chapters trace successive material revolutions. The domestication of the horse and the invention of the chariot and composite bow enabled pastoralist peoples from the borderlands between steppe and civilization to overwhelm the settled kingdoms of Egypt, Mesopotamia, the Indus valley, and China between roughly 1700 and 1400 BC. Keegan argues that the pastoralists' experience of managing and slaughtering animal herds gave them a tactical and psychological advantage over sedentary farmers. The Assyrian empire brought chariot warfare to its fullest expression, creating a long-range military apparatus with supply depots, bridging trains, and ethnically diverse armies.

The cavalry revolution superseded the chariot when selective breeding produced horses strong enough to carry mounted archers. From the Scythians who helped destroy Assyria in 612 BC through the Huns, Turks, and Mongols, the horse peoples brought long-range campaigning at speed, emotional detachment in killing, and the deliberate use of atrocity. Keegan devotes particular attention to the Arab conquests, arguing that Islam dissolved the traditional principles of territoriality and kinship in warfare, and to the Mongol conquests under Genghis Khan, whose combination of discipline, strategic intelligence, and pitiless paganism created the most extensive military domination in history. The horse peoples' most lasting legacy, Keegan argues, was the transmission of their ruthlessness to the settled civilizations they attacked.

The advent of cheap iron democratized access to weapons, enabling Greek city-states to develop phalanx warfare, in which citizen-farmers fought face-to-face in dense ranks until one side broke. Drawing on the military historian Victor Hanson, Keegan identifies this as the invention of "the Western way of war": a commitment to decisive battle that passed from Greece to Rome, from the Roman legions through medieval knighthood, and into the modern European tradition. Rome's centurionate, the first body of professional fighting officers in history, formed the backbone of a military culture that endured for five centuries.

The final chapter traces the gunpowder revolution. In 1494, Charles VIII of France marched mobile cannon into Italy and demolished fortress after fortress, rendering medieval castles obsolete. Italian engineers responded with the angular bastion fortress, whose low, earth-backed walls absorbed cannon fire and restored the advantage of defense. The mounted aristocracy's resistance to the displacement of personal combat by mechanical firepower was gradually overcome through the adoption of musket-bayonet infantry, standardized drill, and professional armies. The French Revolution then created the first citizen army through universal conscription, and Napoleon's campaigns seemed to validate Clausewitz's thesis that war served political ends.

Keegan traces the escalating destructiveness of industrialized warfare through the American Civil War, where railroads and mass-produced weapons proved decisive, to the First World War, where universal military service produced casualty rates that shattered nations and broke armies. The Second World War carried the process further: Adolf Hitler, the leader of Nazi Germany, combined technological obsession, warrior ideology, and Clausewitzian philosophy to wage the most total war in history, culminating in the atomic bombs dropped on Hiroshima and Nagasaki. Keegan presents nuclear weapons as the logical conclusion of the Western technological trend and the ultimate denial of Clausewitz's proposition that war can serve rational political ends.

In his conclusion, Keegan argues that humanity is not doomed to make war: The spirit of cooperativeness, not confrontation, prevails in everyday life, and profound cultural changes such as the abolition of slavery and human sacrifice suggest that warfare may follow a similar trajectory of decline. He characterizes the Western way of warfare as comprising three elements: a moral element inherited from the Greeks, an intellectual element borrowed from Islam's concept of holy war, and a technological element developed through the gunpowder revolution. This combination proved irresistible against all other military cultures but, turned inward, brought catastrophe in the World Wars and threatened annihilation through nuclear weapons. Politics must continue, Keegan maintains, but war in the Clausewitzian sense cannot. Future peacekeepers must learn from what he calls Oriental traditions of evasion, delay, and indirectness, as well as from the primitive world's wisdom of ritual limitation, and must recognize that "politics leading to war are a poisonous intoxication" (436).