How Clausewitz Invented Modern War

Inspired by his combat experience in the Napoleonic wars, Carl von Clausewitz developed theories of warfare so effective that he is still the most quoted man on the battlefield.

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It’s very hard indeed to think of a single thinker or writer who looms as large over their chosen field of study as Carl von Clausewitz. Clausewitz, on the odd chance you haven’t heard of him in this age of wars and rumors of wars, was a Prussian scholar-general. His field of study was warfare—or more precisely, the theory and practice of war, and the vexed, chronically misunderstood relation between the two.

Clausewitz’s magnum opus was begun in 1816 after he’d survived the rigors of more than 30 combat engagements in the revolutionary and Napoleonic wars of Europe, more or less physically intact. The manuscript for On War was left unfinished at the time of his death from a cholera epidemic in 1831, and first published in German in three volumes a few years later by his wife, the former Countess Marie von Bruhl, who possessed a fine, discriminating intelligence, and a passionate devotion to her husband and his life’s work.

What makes Clausewitz’s now longstanding domination of his subject so remarkable is that since his death in 1831, warfare as a field of study has continuously occupied the professional attention of thousands of very smart, thoughtful human beings. A fair number of these men, and a few women, soldiers and civilians alike, have made important contributions to a steadily growing canon of classic works on warfare that began some 2,500 years with Thucydides and Sun Tzu. Yet, when it comes to understanding the nature of war and strategy today, none of the works in that canon is spoken of so often, or with such reverence and respect, as Clausewitz’s On War.

Moreover, since his passing, literally hundreds of wars have been fought, and soldiers and historians have proclaimed uncontroversially that warfare has been transformed and revolutionized not once, but a handful of times.

The American Civil War is generally recognized to be the first industrial war, in which railroads and mass production played a key role. Then came the horrors of World War I, with the advent of tanks and airplanes and poison gas. After that terrible slaughter, the professional military establishments in all the industrialized countries threw out their field manuals, and began again. But they didn’t throw out On War.

Twenty years later came another world war that exploited the tank and the airplane in ways unimaginable to the generals of the First World War, and introduced several new strategic dimensions into warfare: the blitzkrieg, strategic bombing, combined arms war, and finally, nuclear war. Clausewitz not only survived World War II; he emerged from it with his reputation greatly enhanced.

In 1982, Col. Harry Summers’s On Strategy: A Critical Analysis of the Vietnam War masterfully employed Clausewitz’s teachings to offer startling new perspectives on how it was possible for a tiny agricultural country like North Vietnam to defeat the United States. Evoking a key Clausewitzian concept, Summers argued that the Vietnamese communists had struck at America’s critical “center of gravity” in the war—not its army in the field, but the people’s support at home for a distant and ambiguous war—and they had won!

Summers reignited the fiery debate about Vietnam through Clausewitz’s compelling frame of analysis, and On War has remained front and center in the work of American military intellectuals ever since. In 1989, the U.S. Marine Corps issued a new Bible, Field Manual No. 1, to every Marine, with the order to “read it and take it to heart.” Warfighting, its authors freely admitted, was essentially On War in digest form.

Today the official fighting doctrines of the U.S. armed services all draw heavily on Clausewitz unapologetically, and it is next to impossible to find essays in serious defense and military history journals without substantial references to the most famous Prussian officer in history.

Why? The short answer: this brilliant Prussian saw a great deal of combat up close and personal, read military as well as political history and philosophy voraciously, and then wrote, and rewrote, about his subject compulsively for 30 years—often drawing on disciplines far afield from war studies to make his points. He was as much a student of the human soul as he was about war, which lends his writing about the latter a certain breadth and depth that is hard to capture in short essay like this.

In the end, Carl Phillip Gottfried von Clausewitz was able to distinguish war’s timeless elements from its evanescent ones with a laser-like precision that has startled readers for generations, and none more so than this one. This melancholy, introspective Prussian, Professor Donald Stoker argues in his meticulously researched Clausewitz: His Life and Work, was driven above all else by a passion to distinguish himself as one of the great combat soldiers of his generation and ended up producing the most sophisticated and trenchant road map to the study of organized violent conflict yet written: “Clausewitz brought the study of war to a new intellectual level,” Stoker opines, “turning it into a genuine discipline, placing it alongside other fields of study such as art, engineering, or philosophy … No one before or since Clausewitz has used both history and analysis to study war and the forces affecting its conduct so deeply.”

The author of On War, we learn, established his initial reputation in European military circles by exposing the illusions of the pre-eminent strategists of his own time, men who believed that the scientific method and the rationalistic forces of the Enlightenment could be harnessed to make war a science, in which success on the battlefield could be guaranteed merely by working out a series of equations and ratios relating to firepower, terrain, route marches, and supply trains.

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Clausewitz could be intellectually arrogant. He openly scorned the work of the most renowned French strategist of his generation, Antoine-Henri Jomini, and had little good to say in print about his own country’s leading strategist, Adam Heinrich Dietrich von Bulow. These gentlemen, said Clausewitz in brief, had the misfortune of mistaking the accoutrements of war for its essential nature.

“War,” wrote Clausewitz, “is an extreme trial of strength and stamina.” It is “an act of force to compel our enemy to do our will” by spilling blood, and lots of it. It was a duel on a larger scale, with all the uncertainty and danger that implied. In war, he wrote, “everything is uncertain … all military action is intertwined with psychological forces and effects.” So much could go wrong, and so often did! As he famously scribbled, “Fog can prevent the enemy from being seen in time, a gun from firing when it should, a report from reaching the commanding officer. Rain can prevent a battalion from arriving, making another late by keeping it not three but eight hours on the march … Action in war is like movement in a resistant element. Just as the simplest and most natural movements, walking, cannot easily be performed in water, so in war, it is difficult for normal efforts to achieve even moderate results.”

Besides, because war always involves an adversary whose intentions are deliberately masked from us, it “consists of a continuous interaction of opposites.”

Clausewitz’s contemporaries in the strategic arts, and many of his successors in contemporary America and Britain, one hastens to add, have been so captivated by technology’s transformative effects on war as to miss a fundamental truth about war’s nature: it is an unpredictable, supremely violent social process, in which the uncertainties faced by the commander and the soldier alike, and the play of “moral forces” such as courage, self-confidence, fear, exhaustion and danger, invariably cause the most meticulous plans to go awry once the shooting starts. “One might say,” wrote Clausewitz in On War, evoking one of his legion of striking metaphors, “that the physical [factors] seem little more than the wooden hilt, while the moral factors are the precious metal, the real weapon, the fine-honed blade.”

While he homed in on the unchanging essence of war as it was experienced, he was also among the first to see that the Napoleonic wars signaled a sea-change in the way wars were going to be fought in the future—in the complexity of their underlying dynamics, in how they needed to be diagnosed and analyzed with a view to obtaining future success.

In the wake of Prussia’s 1806 humiliating defeat at the hands of France, Clausewitz’s brilliant mentor, Gerd von Scharnhorst, had begun to suss out how Napoleon’s army of poorly trained peasants, with few proper officers and no formal system of administration or supply, could beat the tar off highly disciplined, professional armies of Prussia and her allies. Scharnhorst reckoned correctly that Napoleon’s success was intimately connected with the rise of French nationalism, with the full participation of the populace in the glorious cause of the nation’s martial destiny.

Clausewitz, who had been astonished by Napoleon’s military genius and the resilience of his armies as he had seen them first hand and learned about them through close study, built methodically on Scharnhorst’s insights. Henceforth, war would no longer be restricted to tiny (in relation to population size) professional armies and the princes that led them. Great leaders willing to harness the powers of the people by giving them a stake in the nation’s glory could conduct conflicts on a previously unimaginable scale. The French armies broke all the rules and won, because Napoleon discarded all the normal political and economic constraints that had kept wars limited in time, space, and destructive power for centuries.

Post-Napoleonic War would not be an activity carefully limited in scale by monarchs and carried out by professional soldiers only, with a static set of rules and protocols. It had become a massive, highly volatile national undertaking, best understood as the interaction of a “remarkable trinity,” composed of “primordial violence, hatred and enmity, which are to be regarded as blind natural force; of the play and probability within which the creative spirit is free to roam; and of its element of subordination as an instrument of policy, which makes it subject to reason alone. The first of these three aspects concerns the people; the second the commander and his army; the third the government … When whole communities go to war, whole peoples, the reason always lies in some political situation, and the occasion is always due to some political object. War, therefore, is an act of policy.”

Stoker’s biography was written in part to reconstruct the Master’s largely unreported roles in the various wars in which engaged from 1792 until 1815; to suggest some connections between those experiences and the vast flow of written works he produced when he was away from the battlefield; and to give us some sense of man’s inner life and temperament.

Certainly the vast correspondence between Marie and Carl has been skillfully exploited by Stoker to flesh out our picture of the man. He shows their deep affection, Carl’s dependence on Marie’s love to sustain him through bouts of melancholy and career setbacks, of which there were more than a few, and their unusual (for the time) intellectual partnership. There is ample evidence in the letters to support Stoker’s claim that Clausewitz was consumed by a desire to excel in combat through individual acts of courage, and that he was deeply disappointed that he never commanded more than a single battalion in combat, and then only briefly.

Most of his long career was spent not where he wanted it, but probably where it should have been, given his temperament and inclinations: as a staff officer, a planner and organizer, and as one of the main reformers of the Prussian army after its defeat in 1806.

Clausewitz: His life and Work is a fine, carefully crafted book, but it seems to me it could have more imaginatively illuminated the relationship between its subject’s experience at war and his influential and original ideas if the author had elected to write a more selective narrative, focusing closer attention on those battles and campaigns where we know a fair amount about Clausewitz’s own role in the engagements at hand, and less attention on campaigns in which his role is unclear, or negligible.

As it stands, the book rather heavily foregrounds detailed battle narrative, and Clausewitz, our ostensible subject, fades into the woodwork on a regular basis. At times I felt I was reading a slightly dry, systematic survey of European conflict sprinkled with references to Clausewitz, rather than a study which sought to connect his experience as a soldier to his huge corpus of writing.

Granted, partly this is a problem of sources the author identifies in the introduction. Documents and firsthand accounts of Clausewitz at war by others are few and far between. Still, Prof. Stoker might have been a bit less tentative, a bit more adventurous, in making connections between the life in the field and the ideas in the books, even if the connections were of necessity somewhat speculative.

And readers with little familiarity with European wars of Clausewitz’s time—and there were a great many—will look in vain for “big picture” introductions explaining what was basically at stake in each conflict. The many campaigns have an unfortunate way of blurring into one another.

In many ways Stoker’s battle narrative works best when it gives us rich context for Clausewitz’s own accounts of his combat experience, which are invariably as keenly observed as they are harrowing. Stoker provides an excellent account of the long siege battle on the Rhine at the battle of Mainz in 1793, in which Clausewitz first encounters war’s vast devastation in a night attack on one of the French bastions on the west side of the River:

“Let us accompany a novice to the battlefield. As we approach the rumble of guns grows louder and alternates with the whir of cannonballs, which begin to attract his attention. Shots begin to strike close around us. We hurry up the slope where the commanding general is stationed … Here cannonballs and bursting shells are frequent, and life begins to seem more serious than the young man has imagined … Now we enter the battle raging before us, still almost like a spectacle, and join the nearest divisional commander … A noise is heard that is a certain indication of increasing danger—the rattling of grapeshot on roofs and on the ground. Cannonballs tear past, whizzing in all directions, and musket balls begin to whistle around us … The air is filled with hissing bullets that sound like a sharp crack if they pass close to one’s head. For a final shock, the sign of men being killed and mutilated moves our pounding hearts to awe and pity.”

Such quotes certainly whet the appetite to read more of Clausewitz’s own, more obscure histories of campaigns in which he played a part. Regrettably, not many of them have been adequately translated.

Despite Clausewitz’s unfortunate tendency to permit battle narrative to dominate the main subject, this is an important and worthy book, especially for those who already have a reasonable familiarity with Clausewitz’s thought, and want to gain a sense of the personality and the experiences that gave rise to his ideas. For those less familiar with the ideas, the best place to start is Michael Howard’s recently re-issued classic, Clausewitz: A Very Short Introduction, and Peter Paret’s extraordinarily cogent essays on the man and his work in Understanding War.