Carl Philipp Gottfried von Clausewitz (June 1, 1780 – November 16, 1831) was a Prussian soldier and German military theorist who stressed the moral and political aspects of war. His most notable work, Vom Kriege (On War), was unfinished at his death.

Clausewitz espoused a romantic and Hegelian conception of warfare, though he also had at least one foot planted firmly in the more rationalist ideas of the European Enlightenment. He stressed the dialectic of how opposite factors interact, noting how unexpected developments unfolding under the "fog of war" called for rapid decisions by alert commanders. He saw history as a complex check on abstractions that did not accord with experience. In opposition to Antoine - Henri Jomini he argued war could not be quantified or graphed or reduced to mapwork and graphs. Clausewitz had many aphorisms, of which the most famous is "War is the continuation of policy by other means", a description that has won wide acceptance.

Clausewitz's Christian names are sometimes given in non - German sources as Carl Philipp Gottlieb, Carl Maria, or misspelled Karl, due to reliance on mistaken source material, conflations with his wife's name, Marie, or mistaken assumptions about German orthography. Carl Philipp Gottfried appears on Clausewitz's tombstone and is thus most likely to be the correct version.

Clausewitz was born on June 1, 1780 in Burg bei Magdeburg, Kingdom of Prussia, the fourth and youngest son of a lower middle class family. His grandfather, the son of a Lutheran pastor, had been a professor of theology. Clausewitz's father was once a lieutenant in the Prussian army and held a minor post in the Prussian internal revenue service. Clausewitz entered the Prussian military service at the age of twelve as a Lance - Corporal, eventually attaining the rank of Major - General.

Clausewitz served in the Rhine Campaigns (1793 – 1794) including the Siege of Mainz, when the Prussian army invaded France during the French Revolution, and served in the Napoleonic Wars from 1806 to 1815. He entered the Kriegsakademie (also cited as "The German War School," the "Military Academy in Berlin," and the "Prussian Military Academy") in Berlin in 1801 (age 21), studied the writings of the philosopher Immanuel Kant, and won the regard of General Gerhard von Scharnhorst, the future first chief of staff of the new Prussian Army (appointed 1809). Clausewitz, Hermann von Boyen (1771 – 1848) and Karl von Grolman (1777 – 1843) were Scharnhorst's primary allies in his efforts to reform the Prussian army between 1807 and 1814.

Clausewitz served during the Jena Campaign as aide - de - camp to Prince August. At the Battle of Jena - Auerstedt on October 14, 1806 – when Napoleon invaded Prussia and defeated the massed Prussian - Saxon army commanded by Karl Wilhelm Ferdinand, Duke of Brunswick – he was captured, one of the 25,000 prisoners captured that day as the Prussian army disintegrated. He was 26.

Clausewitz was held prisoner in France from 1807 to 1808. Returning to Prussia, he assisted in the reform of the Prussian army and state. He married the socially prominent Countess Marie von Brühl and socialized with Berlin's literary and intellectual elite. Opposed to Prussia's enforced alliance with Napoleon I, he left the Prussian army and served in the Russian army from 1812 to 1813 during the Russian Campaign, including at the Battle of Borodino. Like many Prussian officers living in Russia he joined the Russian - German Legion, in 1813. In the service of the Russian Empire, Clausewitz helped negotiate the Convention of Tauroggen (1812), which prepared the way for the coalition of Prussia, Russia, and the United Kingdom that ultimately defeated Napoleon and his allies.

In 1815, the Russo - German Legion was integrated into the Prussian Army and Clausewitz re-entered Prussian service. He was soon appointed chief of staff of Johann von Thielmann's III Corps. In that capacity, he served at the Battle of Ligny and the Battle of Wavre during the Waterloo Campaign in 1815. The Prussians were defeated at Ligny (south of Mont - Saint - Jean and the village of Waterloo) by an army led personally by Napoleon, but Napoleon's failure to destroy the Prussian forces led to his defeat a few days later at the Battle of Waterloo, when the Prussian forces arrived on his right flank late in the afternoon and joined the Anglo - Dutch forces pressing his front.

Clausewitz was promoted to Major - General in 1818 and appointed director of the Kriegsakademie, where he served until 1830. In that year the outbreak of several revolutions around Europe and a crisis in Poland appeared to presage another major European war. Clausewitz was appointed chief of staff of the only army Prussia was able to mobilize, which was sent to the Polish border. He died after commanding the Prussian army's efforts to construct a 'cordon sanitaire' to contain the great cholera outbreak in 1831 (the first time cholera had appeared in Europe, causing a continent - wide panic). His widow was left to publish his magnum opus on the philosophy of war in 1832, which he had started working on in 1816 but had not completed.

Clausewitz was a professional soldier who was involved in numerous military campaigns, but he is famous primarily as a military theorist interested in the examination of war. He wrote a careful, systematic, philosophical examination of war in all its aspects, as he saw it and taught it. The result was his principal work, On War, the West's premier work on the philosophy of war. It was only partially completed by the time of his death, but just how close to completion it was is a matter of considerable scholarly debate. Clausewitz constantly sought to revise the text, particularly between 1827 and his departure on his last field assignment, to include more material on "people's war" and forms of war other than between states, but little of this material was included in the book. Soldiers before this time had written treatises on various military subjects, but none had undertaken a great philosophical examination of war on the scale of Clausewitz's and Leo Tolstoy's, both of which were inspired by the events of the Napoleonic Era.

Clausewitz's work is still studied today, demonstrating its continued relevance. More than ten major English language books focused specifically on his work were published between 2005 and 2010. Lynn Montross, writing on that topic in War Through the Ages (1960), said; "This outcome... may be explained by the fact that Jomini produced a system of war, Clausewitz a philosophy. The one has been outdated by new weapons, the other still influences the strategy behind those weapons." Although Jomini also wrote extensively on war, he did not attempt to define war. Clausewitz did, providing the following definition:

Clausewitz introduced systematic philosophical contemplation into Western military thinking, with powerful implications not only for historical and analytical writing but also for practical policy, military instruction, and operational planning. He relied on his own experiences, contemporary writings about Napoleon, and on historical sources. His historiographical approach is evident in his first extended study, written when he was 25, of the Thirty Years War. He rejects the Enlightenment's view of the war as a chaotic muddle and instead explains its drawn out operations by the economy and technology of the age, the social characteristics of the troops, and the commanders' politics and psychology. In On War, Clausewitz sees all wars as the sum of decisions, actions, and reactions in an uncertain and dangerous context, and also as a socio - political phenomenon. He has several definitions, the most famous one being that war is the continuation of politics by other means. He also stressed the complex nature of war, which encompasses both the socio - political and the operational and stresses the primacy of state policy.

The word "strategy" had only recently come into usage in Modern Europe, and Clausewitz's definition is quite narrow: "the use of engagements for the object of war." Some modern readers find this narrow definition disappointing, but his focus was on the conduct of military operations in war, not on the full range of the conduct of politics in war. Nonetheless, Clausewitz conceived of war as a political, social, and military phenomenon which might — depending on circumstances — involve the entire population of a nation at war. In any case, Clausewitz saw military force as an instrument that states and other political actors use to pursue the ends of policy, in a dialectic between two opposing wills, each with the aim of imposing his policies and will upon his enemy.

Clausewitz's emphasis on the inherent superiority of the defense suggests that habitual aggressors are likely to end up as failures. However, the inherent superiority of the defense obviously does not mean that the defender will always win: there are other asymmetries to be considered. He was interested in cooperation between the regular army and militia or partisan forces, or citizen soldiers, as one possible — sometimes the only — method of defense. In the circumstances of the Wars of the French Revolution and with Napoleon, which were energized by a rising spirit of nationalism, he emphasized the need for states to involve their entire populations in the conduct of war. This point is especially important, as these wars demonstrated that such energies could be of decisive importance and for a time led to a democratization of the armed forces much as universal suffrage democratized politics.

While Clausewitz was intensely aware of the value of intelligence at all levels, he was also very skeptical of the accuracy of much military intelligence: "Many intelligence reports in war are contradictory; even more are false, and most are uncertain.... In short, most intelligence is false." This circumstance is generally described as the fog of war. Such skeptical comments apply only to intelligence at the tactical and operational levels; at the strategic and political levels he constantly stressed the requirement for the best possible understanding of what today would be called strategic and political intelligence. His conclusions were influenced by his experiences in the Prussian Army, which was often in an intelligence fog due partly to the superior abilities of Napoleon's system but even more to the nature of war. Clausewitz acknowledges that friction creates enormous difficulties for the realization of any plan, and the fog of war hinders commanders from knowing what is happening. It is precisely in the context of this challenge that he develops the concept of military genius, whose capabilities are seen above all in the execution of operations.

Clausewitz's "fascinating trinity" (wunderliche Dreifaltigkeit) comprises (1) a blind impulse, located in the people and their passions, including hate and enmity, (2) free will, which belongs to the army and its leader and includes chance and probability, and (3) pure reason, which pertains to the government. The theory of war needs to deal with all three factors.

Key ideas discussed in On War include:

• the dialectical approach to military analysis
• the methods of "critical analysis"
• the nature of the balance - of - power mechanism
• the relationship between political objectives and military objectives in war
• the asymmetrical relationship between attack and defense
• the nature of "military genius" (involving matters of personality and character, beyond intellect)
• the "fascinating trinity" (wunderliche Dreifaltigkeit) of war
• philosophical distinctions between "absolute" or "ideal war," and "real war"
• in "real war," the distinctive poles of a) limited war and b) war to "render the enemy helpless"
• "war" belonging fundamentally to the social realm — rather than to the realms of art or science
• "strategy" belonging primarily to the realm of art
• "tactics" belonging primarily to the realm of science
• the importance of "moral forces" (more than simply "morale") as opposed to quantifiable physical elements
• the "military virtues" of professional armies (which do not necessarily trump the rather different virtues of other kinds of fighting forces)
• conversely, the very real effects of a superiority in numbers and "mass"
• the essential unpredictability of war
• the "fog" of war
• "friction" - the disparity between the ideal performance of units, organization or systems and their actual performance in real world scenarios
• strategic and operational "centers of gravity"
• the "culminating point of the offensive"
• the "culminating point of victory"

Clausewitz used a dialectical method to construct his argument, leading to frequent misinterpretation of his ideas. British military theorist B.H. Liddell Hart contends that the enthusiastic acceptance by the Prussian military establishment – especially Moltke the Elder – of what they believed to be Clausewitz's ideas, and the subsequent widespread adoption of the Prussian military system worldwide, had a deleterious effect on military theory and practice, due to their egregious misinterpretation of his ideas:

As so often happens, Clausewitz's disciples carried his teaching to an extreme which their master had not intended.... [Clauswitz's] theory of war was expounded in a way too abstract and involved for ordinary soldier - minds, essentially concrete, to follow the course of his argument – which often turned back from the direction in which it was apparently leading. Impressed yet befogged, they grasped at his vivid leading phrases, seeing only their surface meaning, and missing the deeper current of his thought.

As described by Christopher Bassford, professor of strategy at the National War College of the United States:

One of the main sources of confusion about Clausewitz's approach lies in his dialectical method of presentation. For example, Clausewitz's famous line that "War is a mere continuation of politics by other means," ("Der Krieg ist eine bloße Fortsetzung der Politik mit anderen Mitteln") while accurate as far as it goes, was not intended as a statement of fact. It is the antithesis in a dialectical argument whose thesis is the point – made earlier in the analysis – that "war is nothing but a duel [or wrestling match, a better translation of the German Zweikampf] on a larger scale." His synthesis, which resolves the deficiencies of these two bold statements, says that war is neither "nothing but" an act of brute force nor "merely" a rational act of politics or policy. This synthesis lies in his "fascinating trinity" [wunderliche Dreifaltigkeit]: a dynamic, inherently unstable interaction of the forces of violent emotion, chance, and rational calculation.

Another example of this confusion is the idea that Clausewitz was a proponent of total war as used in the Third Reich's propaganda in the 1940s. He did not use the term: rather, he discussed "absolute war" or "ideal war" as the purely logical result of the forces underlying a "pure," Platonic "ideal" of war. In what he called a "logical fantasy," war cannot be waged in a limited way: the rules of competition will force participants to use all means at their disposal to achieve victory. But in the real world, such rigid logic is unrealistic and dangerous. As a practical matter, the military objectives in real war that support political objectives generally fall into two broad types: "war to achieve limited aims"; and war to "disarm" the enemy, "to render [him] politically helpless or militarily impotent." Thus the complete defeat of the enemy may not be necessary, desirable, or even possible.

In modern times the reconstruction of Clausewitzian theory has been a matter of some dispute. One analysis was that of Panagiotis Kondylis, a Greek - German writer and philosopher, who opposed the interpretations of Raymond Aron in Penser la Guerre, Clausewitz, and other liberal writers. According to Aron, Clausewitz was one of the first writers to condemn the militarism of the Prussian general staff and its war proneness, based on Clausewitz's argument that "war is a continuation of politics by other means." In Theory of War, Kondylis claims that this is inconsistent with Clausewitzian thought. He claims that Clausewitz was morally indifferent to war (though this probably reflects a lack of familiarity with personal letters from Clausewitz, which demonstrate an acute awareness of war's tragic aspects) and that his advice regarding politics' dominance over the conduct of war has nothing to do with pacifist ideas. For Clausewitz, war is simply a means to the eternal quest for power, of raison d'État in an anarchic and unsafe world.

Other notable writers who have studied Clausewitz's texts and translated them into English are historians Peter Paret of Princeton University and Sir Michael Howard, and the philosopher, musician, and game theorist Anatol Rapoport. Howard and Paret edited the most widely used edition of On War (Princeton University Press, 1976 / 1984) and have produced comparative studies of Clausewitz and other theorists, such as Tolstoy. Bernard Brodie's A Guide to the Reading of "On War", in the 1976 Princeton translation, expressed his interpretations of the Prussian's theories and provided students with an influential synopsis of this vital work.

The British military historian John Keegan has attacked Clausewitz's theory in his book A History of Warfare. Keegan argued that Clausewitz assumed the existence of states, yet 'war antedates the state, diplomacy and strategy by many millennia'.

Clausewitz died without completing On War, but despite this his ideas have been widely influential in military theory and have had a strong influence on German military thought specifically. Later Prussian and German generals such as Helmuth Graf von Moltke were clearly influenced by Clausewitz: Moltke's notable statement that "No campaign plan survives first contact with the enemy" is a classic reflection of Clausewitz's insistence on the roles of chance, friction, "fog", uncertainty and interactivity in war.

After 1890 or so, Clausewitz's influence spread to British thinking as well. One example is naval historian Julian Corbett (1854 – 1922), whose work reflected a deep if idiosyncratic adherence to Clausewitz's concepts. Clausewitz had little influence on American military thought before 1945, but influenced Karl Marx, Friedrich Engels, Vladimir Lenin and Mao Zedong, and thus the Communist and Soviet traditions, as Lenin emphasized the inevitability of wars among capitalist states in the age of imperialism and presented the armed struggle of the working class as the only path toward the eventual elimination of war. Because Lenin was an admirer of Clausewitz and called him "one of the great military writers", his influence on the Red Army was immense. The Russian historian A.N. Mertsalov commented that "It was an irony of fate that the view in the USSR was that it was Lenin who shaped the attitude towards Clausewitz, and that Lenin's dictum that war is a continuation of politics is taken from the work of this anti - humanist anti - revolutionary." Clausewitz directly influenced Mao Zedong, who read On War in 1938 and organized a seminar on Clausewitz as part of the educational program for the Party leadership in Yan'an. Thus the "Clausewitzian" content in many of Mao's writings is not merely second - hand knowledge via Lenin (as many have supposed), but reflects Mao's own in-depth study.

The idea that war involves inherent "friction" that distorts, to a greater or lesser degree, all prior arrangements, has become common currency in fields such as business strategy and sport. The phrase fog of war derives from Clausewitz's stress on how confused warfare can seem while immersed within it. The term center of gravity, used in a military context derives from Clausewitz's usage, which he took from Newtonian Mechanics. In U.S. military doctrine, "center of gravity" refers to the basis of an opponent's power, at the operational, strategic, or political level, though this is only one aspect of Clausewitz's use of the term.

After 1970, some theorists claimed that nuclear proliferation made Clausewitzian concepts obsolete after the 20th century period in which they dominated the world. John E. Sheppard, Jr., argues that by developing nuclear weapons, state based conventional armies simultaneously both perfected their original purpose, to destroy a mirror image of themselves, and made themselves obsolete. No two powers have used nuclear weapons against each other, instead using conventional means or proxy wars to settle disputes. If such a conflict did occur, presumably both combatants would be annihilated.

The end of the 20th century and the beginning of the 21st century have seen many instances of state armies attempting to suppress insurgencies, terrorism, and other forms of asymmetrical warfare. If Clausewitz focused solely on wars between countries with well defined armies, as many commentators have argued, then perhaps On War has lost its analytical edge as a tool for understanding war as it is currently fought. This is an ahistorical view, however, for the era of the French Revolution and Napoleon was full of revolutions, rebellions and violence by "non-state actors", such as the wars in the French Vendée and in Spain. Clausewitz wrote a series of “Lectures on Small War” and studied the rebellion in the Vendée (1793 - 1796) and the Tyrolean uprising of 1809. In his famous “Bekenntnisdenkschrift” of 1812, he called for a “Spanish war in Germany” and laid out a comprehensive guerrilla strategy to be waged against Napoleon. In On War he included a famous chapter on “The People in Arms.”

One prominent critic of Clausewitz is the Israeli military historian Martin van Creveld. In his book The Transformation of War, Creveld argued that Clausewitz's famous "Trinity" of people, army, and government was an obsolete socio - political construct based on the state, which was rapidly passing from the scene as the key player in war, and that he (Creveld) had constructed a new "non - trinitarian" model for modern warfare. Creveld's work has had great influence. Daniel Moran replied, 'The most egregious misrepresentation of Clausewitz’s famous metaphor must be that of Martin van Creveld, who has declared Clausewitz to be an apostle of Trinitarian War, by which he means, incomprehensibly, a war of 'state against state and army against army,' from which the influence of the people is entirely excluded." Christopher Bassford went further, noting that one need only read the paragraph in which Clausewitz defined his Trinity to see "that the words 'people,' 'army,' and 'government' appear nowhere at all in the list of the Trinity’s components.... Creveld's and Keegan's assault on Clausewitz's Trinity is not only a classic 'blow into the air,' i.e., an assault on a position Clausewitz doesn't occupy. It is also a pointless attack on a concept that is quite useful in its own right. In any case, their failure to read the actual wording of the theory they so vociferously attack, and to grasp its deep relevance to the phenomena they describe, is hard to credit."

Some have gone further and suggested that Clausewitz's best known aphorism, that war is a continuation of policy by other means, is not only irrelevant today but also inapplicable historically. Others argue that the essentials of Clausewitz's theoretical approach remain valid, but that our thinking must adjust to the realities of particular times and places. Knowing that "war is an expression of politics by other means" does us no good unless we use a definition of "politics" that is appropriate to the circumstance and to the cultural proclivities of the combatants in each situation; this is especially true when warfare is carried on across a cultural or civilizational divide, and the antagonists do not share as much common background as did many of the participants in the First and Second World Wars.

In military academies, schools and universities worldwide, Clausewitz's literature is mandatory reading.