On War

Overview

About six hundred pages, an unfinished treatise by the Prussian general and military theorist Carl von Clausewitz, assembled and published posthumously by his widow Marie von Clausewitz in 1832 from manuscripts he had been revising, in some cases repeatedly and with genuine dissatisfaction, over roughly the last decade of his life. Clausewitz had served through the Napoleonic Wars, including at Borodino and Waterloo, and drew on this direct, extensive combat experience, together with wide historical reading, to attempt something no earlier military writer had really achieved: not a manual of tactics or a set of prescriptive maxims for specific situations, but a general theory of what war actually is, beneath the surface variation of weapons, terrain, era and opposing forces.

The book’s unfinished state is itself worth understanding before reading it. Clausewitz died of cholera in 1831 having substantially revised only the first chapter of Book I to his own satisfaction, and left a note indicating he considered much of the rest still a rough manuscript requiring further work, a fact that helps explain some genuine tensions and apparent contradictions between different sections, most notably around how absolutely the book’s most famous claims should be taken.

The argument

War as the continuation of policy. The book’s most famous and most consequential claim, stated in its first chapter, is that war is nothing but the continuation of political intercourse by other, violent means, a formulation that subordinates military action entirely to political purpose. War, on this account, has no legitimate logic of its own separate from the political goal that justified beginning it, and Clausewitz insists that commanders and statesmen who lose sight of this relationship risk pursuing military victories that serve no coherent political end, or fighting wars whose violence has escaped rational political control altogether.

The trinity of violence, chance and reason. Clausewitz’s second major theoretical contribution describes war’s essential nature as a trinity of three distinct forces in tension: the primordial violence, hatred and enmity most naturally associated with the people; the play of chance and probability that governs the army and its commander, operating within genuine uncertainty; and war’s element of subordination to policy, which makes it, ultimately, an instrument of the government’s rational calculation. Real wars, Clausewitz suggests, vary enormously depending on how these three forces balance against one another in any particular conflict, which is part of why no single set of tactical maxims can capture war’s full range.

Absolute war and real war. Clausewitz distinguishes between war in its pure theoretical form, absolute war, an extreme of unlimited violence pursued to its logical conclusion, and real war as it is actually fought, always constrained, moderated and complicated by political limits, resource constraints, and the practical difficulties of actually executing military plans. This distinction lets Clausewitz reason rigorously about war’s theoretical extremes while still accounting for the messier, incomplete, compromise-laden character of actual historical conflicts.

Friction. One of the book’s most durable and widely cited concepts describes the countless small difficulties, delays, miscommunications and unforeseen obstacles that separate a battle plan on paper from its actual execution in the field. Clausewitz argues that everything in war is individually simple, but that these simple difficulties accumulate into a friction no one who has not experienced actual combat can fully imagine, a friction that explains why even brilliant strategic plans routinely fail to unfold as intended.

Strategy, the culminating point, and the superiority of defence. In the book’s later sections, Clausewitz works through more specific strategic concepts, including the culminating point of the attack, the moment past which an offensive’s momentum and resources are exhausted and continuing to advance becomes counterproductive, and a genuinely counterintuitive argument that defence, properly understood, is actually the inherently stronger form of war, since the defender holds the advantage of terrain, supply lines and the ability to wait for the attacker’s own exhaustion before striking decisively.

How to read it

Read Book I, and especially its first chapter, as the most carefully finished and most theoretically authoritative section of the book; Clausewitz himself considered it the only portion revised to his full satisfaction, and its central claims, the continuation of policy, the trinity, frame everything that follows.

Approach the later books with some awareness that they represent earlier, less polished drafts, and be alert to apparent tensions between sections, particularly around how absolutely to take the continuation-of-policy formula, since scholars have long debated whether Clausewitz meant it as a strict definitional claim or a looser, more qualified generalization.

Read the friction concept as something closer to a general theory of the gap between planning and execution than a narrowly military idea; it has been applied well beyond warfare, in business strategy and organizational theory among other fields, precisely because it captures something true about complex human undertakings generally.

Pay attention to how much of Clausewitz’s argument depends on distinguishing theoretical extremes, absolute war, from practical reality, real war, a method of reasoning that lets him make strong claims about war’s essential nature without being immediately refuted by any specific historical counterexample.

Read this book against a basic outline of the Napoleonic Wars, since Clausewitz draws constantly, if often implicitly, on Napoleon’s campaigns as his primary source of concrete military example, and understanding this historical background sharpens many otherwise abstract-seeming passages.

Questions it raises

• Does subordinating war entirely to political purpose, as Clausewitz’s central formula insists, adequately describe wars that seem to escape rational political control once begun, driven instead by accumulated hatred, momentum or internal military logic?
• Clausewitz’s trinity assigns war’s essential character to the people’s passion, the army’s exposure to chance, and the government’s reason. How well does this three-part model apply to modern warfare, where the boundaries between people, army and government are often far less distinct than in Clausewitz’s own era?
• Is the concept of friction primarily a practical military observation, or does it function as something closer to a general theory of why any complex human plan tends to fail in execution? How far can the concept be usefully extended beyond warfare?
• Clausewitz argues defence is the inherently stronger form of war. Does this claim hold up given how many historical conflicts have been decided by decisive offensive action, or does Clausewitz’s argument rest on a narrower, more technical sense of strength than ordinary usage assumes?
• The book was left unfinished at Clausewitz’s death, with the author himself expressing dissatisfaction with much of the manuscript. How should a reader weigh apparent contradictions between sections, as genuine unresolved tensions in Clausewitz’s thinking, or as artifacts of incomplete revision that a finished version might have resolved?
• Given how directly Clausewitz draws on the Napoleonic Wars for his examples, how much of his theory represents insight into war’s nature that holds across eras, and how much reflects the specific military conditions, mass conscript armies, decisive set-piece battles, of his own particular historical moment?