Decoding Clausewitz: A New Approach to On War, by Jon Tetsuro Sumida, University Press of Kansas, 2008. Pp. xix, 234. $29.95.

Decoding Clausewitz is fun, elegant, thought-provoking, and sometimes convincing. [Sumida's] description of On War “as a set of instructions on how to engage in serious learning of a highly personal nature rather than an impersonal representation of the totality of that which is to be learned” is as intelligent an explanation of the book as one is likely ever to read. Those of us who teach military history in an effort to educate soldiers will find in Decoding Clausewitz an inspiring explanation of what we ought to be doing.

Almost everything in On War is very simple, but the simplest things are so difficult that no previous reader has comprehended Carl von Clausewitz. Or so Jon Sumida would have one believe. The fundamental thesis of Decoding Clausewitz is that, a great deal of “intelligent, rigorous, and productive” study notwithstand ing, previous interpreters of Carl von Clausewitz’s masterwork have missed the point (p.1). Or rather, three points: that Clausewitz had virtually completed On War by the time of his death, that the superiority of defense to offense is the work’s dominant idea, and that Clausewitz sought to present not a comprehensive theory of war but a scientific method by which each individual can prepare himself to practice war knowledgeably. On War is a practical handbook for the peacetime education of wartime commanders, and the essence of that education is “the mental reenactment of historical case studies of command decision” (p.3).

Sumida is a critic by nature; he devotes a good part of his short book to viewing Clausewitz in the reflection of others’ unsatisfactory reactions to On War. In this vein, the preface offers a trenchant discussion of the way what Sumida calls “selective engagement” has vitiated efforts to profit from reading Clausewitz in the institutions of professional military education within the armed forces of the United States (p.xii). There follow brief discussions of Antoine-Henri Jomini’s dismissal of On War, Sir Julian Corbett’s implicit borrowing of key ideas, and B. H. Liddell Hart’s excoriation of the ideas he believed responsible for the carnage of the Great War.

After dealing with these three theorists’ treatments of Clausewitz, Sumida turns to the scholarly critiques of On War by Raymond Aron, Peter Paret, and W. B. Gallie. For Sumida, Aron’s charge that Clausewitz’s unfinished work lacks a comprehensive theory of war misses the point that On War was essentially complete. Clausewitz did not offer a comprehensive theory because that was not his purpose, not because he had not yet gotten around to it.

Paret shares Aron’s belief in On War’s unfinished condition and the conviction that its deficiencies would have been rectified in the final product. In Paret’s view, the revisions would have emphasized the political nature of war and emphasized the distinction between limited and absolute war. But his interest in Clausewitz’s political development led Paret, believes Sumida, to miss the military arguments at the core of Clausewitz’s work.

W. B. Gallie, though less famous among students of military theory than either Aron or Paret, came closer to grasping the nature of On War. A philosopher who published studies of Charles Sanders Peirce and R. G. Collingwood, and was heavily influenced by the preeminent philosopher Ludwig Wittgenstein, Gallie treated Clausewitz as a fellow philosopher, a thinker about war rather than a prescriber. Clausewitz treated war as a social phenomenon. Since war lacks principles and is not amenable to logically complete answers, the ability to make judgments, what Clausewitz referred to as “genius,” is a military commander’s crucial quality.

Gallie treats On War as a significant but imperfect work whose truth remains to be revealed “only when the flaws in [Clausewitz’s] conceptual system are exposed and adequately corrected” (p.77). Sumida believes that Gallie, though he pointed the way to understanding On War, mistook his own failures of interpretation for flaws on Clausewitz’s part. In the second half of Decoding Clausewitz, Sumida builds on Gallie’s theories by focusing on the Prussian theorist’s notion of historical reenactment.

Since the argument for the value of historical reenactment rests on historical study itself, Sumida briefly and cogently sketches the process by which Clausewitz learned from his historical experience of Prussia’s defeat by Napoleon and Napoleon’s defeat by Russia. From these events, and more generally from the wars he lived through from 1792 to 1815, Clausewitz derived two key ideas: the superiority of the defense, especially when followed by counterattack, and the potential of a people’s war.

Clausewitz’s appreciation of the pedagogical role of history grew during his appointment as tutor to Crown Prince Frederick William of Prussia. To guide the prince, Clausewitz sought not only to understand war but also to determine how commanders could be taught. He concluded that the only way to develop the intellectual and moral faculties necessary for command was through mental reenactment of complex historical events. On War, his final presentation of the procedure, taught “how to explore realms of personal thought that included emotional elements in relation to the sorts of difficult problem-solving likely to arise in the course of decision-making in war” (pp.100–101).

Sumida argues that Clausewitz’s theory of self-education through historical reenactment reflected precocious understandings both of the nature of language and of the scientific method. Even more striking was his anticipation of the historian R. G. Collingwood’s notion of reenactment as a method of understanding history.

Sumida closes this central chapter of Decoding Clausewitz with brief discussions of Alan Beyerchen’s argument about Clausewitz’s understanding of war’s nonlinearity and Guy Claxton’s cognitive research into the role of intuition. Both of these studies reinforce the value of the method Sumida imputes to Clausewitz. Historical reenactment prepares the mind to deal with nonlinear events by developing the intuitive capacity that Claxton sees as providing “good judgment in hard cases” (p.119).

So smoothly has Sumida corralled Aron, Paret, Gallie, Peirce, Collingwood, and Wittgenstein into his analysis that his own exegesis of On War in the fourth chapter of the book seems almost redundant. The opening section, “Absolute War and Genius,” begins, however, with jarring dismissal of any apparent contradiction between Clausewitz’s initial treatment of absolute war as an abstraction and Sumida’s later acknowledgment “that war that involves that unrestrained use of violence can occur and thus presumably is also real” (p.123, author’s italics). For the rest of the book, the author refers insouciantly to “(real) absolute war” and “defensive (real) absolute war,” which can also be “limited war” (p.125). If this were not complicated enough, there is also the contrast between (real) absolute war and “(less than absolute) real war” (p.136). One can defer the chore of working out the exact difference between the two forms of war—or the two forms of brackets. As Sumida says in one of the more opaque passages of the book, “because the potential for (real) absolute war is contained within [less than absolute] real war, the two forms are conjoined rather than distinct taxonomic categories until after the conflict has ended, at which time the occurrence or nonoccurrence of escalation in violence has been established as fact” (p.169, author’s brackets). There has to be a more plausible understanding of Clausewitz’s use of “absolute war.”

Sumida’s discussion of genius—of the intellectual qualities of the true military commander—is as compelling as his notion of “absolute war” is not. Having established that Clausewitz believed in the centrality of genius and that both the conscious and unconscious elements of military intellect could be taught, the author moves naturally to the relationship between history and theory in the process of historical reenactment. History may be the basic arena in which the imagination plays its educational games, but the historical record is full of holes. In the absence of evidence, crucial causal connections are unclear. To produce a useful history requires that gaps be filled—validly, if not with perfect historical accuracy. It is the role of theory, of critical analysis, to provide rigorous solutions to historical questions. As depicted in an appendix, Clausewitz’s critical analysis is the process by which Verifiable Historical Fact combines with Theory-Based Historical Surmise to produce Synthetic Experience, which combines in turn with Reflection on Synthetic Experience to produce Improved Capacity for Judgment (p.196).

Armed with the intellectual tool of critical analysis, the student of war is now ready to use it in deriving the central lesson of On War—that defense is the stronger form of war. The statement itself is hardly exceptional since Clausewitz clearly chose to devote the longest chapter of On War to the defense, but Sumida brings out a number of less obvious points. Of particular interest are his observation that Book 7, “The Attack,” contains numerous backhanded references to the defenders’ advantages and Sumida’s discussion of Clausewitz’s attitude toward a people’s war.

The concluding chapter offers a thorough summary of the book’s argument, and many readers will find it a good place to start. For although the writing is clear, the plot’s twists and turns may baffle the uninitiated. Sumida’s argument is more fun if one knows where it is going.

Decoding Clausewitz is fun, elegant, thought-provoking, and sometimes convincing. His description of On War “as a set of instructions on how to engage in serious learning of a highly personal nature rather than an impersonal representation of the totality of that which is to be learned” (p.5, author’s italics) is as intelligent an explanation of the book as one is likely ever to read. Those of us who teach military history in an effort to educate soldiers will find in Decoding Clausewitz an inspiring explanation of what we ought to be doing.

Still, one can believe most of what Sumida says and feel that questions, both methodical and substantive, remain unanswered. The author’s discovery that Clausewitz beat Collingwood to the practice of historical reenactment is fascinating but implies that On War became comprehensible only after Collingwood reinvented the technique. That argument helps to explain why previous Clausewitz scholars failed to see the central themes of On War, but it raises the “tree falling in the forest” question. If Collingwood had not been heard—if Gallie had not heard Collingwood and Sumida had not heard Gallie—would On War exist as a book about historical reenactment?

Sumida’s economical reading of On War also leaves one wondering about those sections that do not concern the strength of the defensive or critical analysis and, at the least, dilute the message. If his intent was to offer a clear protocol for understanding war, Clausewitz might have done his future readers the favor of using his own method of critical analysis to place himself mentally in their shoes. Surely the exercise of reenacting the reading of his own book while imagining himself to be of mere mortal intelligence would have shown him that On War is a more difficult book than it need be. It might even have spurred him to undertake some revisions.

Dr. Eugenia C. Kiesling is professor of history at the United States Military Academy. Educated at Yale, Oxford, and Stanford universities, she is the author of Arming Against Hitler: France and the Limits of Military Planning (Lawrence, Kans., 1996) and the editor and translator of Admiral Raoul Castex’s Strategic Theories (Annapolis, Md., 1994).

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