The Spirit of the Age: Clausewitz on Limited and Absolute War

How the Socio-Political Defines the Militarily Possible

In 1806, Prussia declared war on Napoleonic France. To understate matters slightly, the Prussian army did not impress. At the twin battles of Jena and Auerstedt, Prussia suffered a defeat of uncommon humiliation. A single French corps, outnumbered two-to-one, defeated the army that considered itself the premier land power of Europe. Napoleon himself could not believe the report of his Marshal Davout that the Prussians were beaten, remarking of the bespectacled marshal to his aide-de-camp, “Your marshal must be seeing double.” This defeat proved to be so demoralizing that Prussian fortresses began to surrender without a fight, often to humiliatingly small French forces. Clausewitz was captured at Jena and spent the next year in French captivity, watching helplessly as his country was reduced to a French client state. He was 26 at the time. 

This was to be a formative experience. Imprisoned, Clausewitz had plenty of time to consider how this calamity had come about. He perceived clearly that he had witnessed a revolution in military affairs. He was not alone in this perception, however Clausewitz was exceptional in his understanding of French victory as not just a superiority in training and tactics, but of the state’s ability to harness social and political forces. As he elaborated in On War, the armies and states of the 18th century were so preoccupied with the rules of war that they were familiar with that they failed to comprehend the military effects of the new order created by the French Revolution. 

Clausewitz as a Young Man

Clausewitz, influenced by the Romantic movement, attributed these changes to the “spirit of the age.” While this phrasing is typical of the 19th century, he is explicitly referring to changes in the social and political conditions that affect both the circumstances and means in which wars are fought. The French Revolution unleashed forces that allowed France to use means (such as the levée en masse) that were previously impossible to increase its military strength beyond that of its rivals. 

A common misreading of Clausewitz is to understand that he believed that the methods of his own epoch were superior to those of the past. Indeed, many of his contemporaries made this mistake and it is no less common today. This reflects a common form of chauvinism towards the past where we imagine that the differences between contemporary arrangements and those of the past are a product of our intellectual superiority. 

Rather, Clausewitz as an astute student of history understood that the methods of the past were rational in their contexts. The feudal order of war fought by knights and retinues dominated medieval Europe because it was suitable to the existing political and social relations. It was not that people of that time lacked the ability to imagine the concept of mercenary, professional, or mass armies that dominated later epochs but that they were unsuitable for the circumstances. Harold Godwinson could not have conducted a levée en masse to improve his chances at Hastings in 1066. A mob of confused Anglo-Saxons with sticks would not have upended the balance of power in the same way that the French armies of the Revolution had. In Clausewitz’s view, it was an absurdity to seek to apply one circumstance's methods of war to another time. The methods of Napoleonic War would have ill-suited Frederick the Great, just as the methods of Frederick the Great led Prussia to disaster at the Battle of Jena. it was not that these methods were worse it is that they were unsuitable for the circumstances. 

Thus, in Clausewitz’s view, Napoleon’s grand achievement was not (as other argued) in illuminating a superior form of war, but rather his genius was in finding the form of war most suitable to contemporary social and political conditions. In his view, it was not that the French Revolution and the popular wars it unleashed were a progression past the cabinet wars of the 18th century. Rather, it was that the French (and Bonaparte especially) succeeded in recognizing the spirit and character of the time. Napoleon's methods of war were suitable to the socio-political environment that existed. However, this was no less the case of Frederick the Great.  Clausewitz thus rejects any idea of teleology to the development of war. In his view, the great commanders of history should not be seen as contributing towards a more perfect or “correct” form of war but rather each striving to to master war as it exists in their own time. 

Thus, Clausewitz did not reject the legitimacy of norms and rules as a part of international relations and warfare. The limited “cabinet wars” of the 18th century were rational in their context. But he viewed the Napoleonic Wars and Prussia’s humiliation as clear evidence not to trust a state’s security to them. Norms and rules have both force and purpose when the socio-political environment provides it. Placing too much faith in them risks that “Sooner or later someone will come along with a sharp sword and hack off our arms.” 

The “spirit of the age” may ensure that the conduct of war is limited and remains far from its absolute form, but Clausewitz impresses upon us the fact that at any time, with all the suddenness of a revolution, conditions may change and allow a more absolute form of war.  

This returns us to one of On War’s most fundamental aphorisms: “War has its own grammar but not its own logic.” The “logic of war” is instead borrowed from the realm of politics. Thus, the conduct of war will shift not only with the introduction of new methods and technologies, but with changes in the state of politics and the manner in which society engages with politics. 

This observation is of vital importance as it explains why it is easy for the study of military history and even personal experience to be misleading. A purely military point of view can lead one to attempt to derive lessons of war without thorough consideration of the political circumstances. This was a mistake made by many commentators in the leadup to the First Gulf War who expected a bloody quagmire based on the American experience in Vietnam. Recency bias was substituted for a careful examination of the conditions in which the war takes place. No less destructive, as in the case Clausewitz was most personally familiar with, is blind faith in the successful methods of the past. This led to ignorance of the social and political conditions which made their employment effective. The methods of Frederick the Great had brought Prussia the status of great power during the Seven Years’ War but were utterly unsuited to the era of mass armies unleashed by the nationalist fervor that emerged from the French Revolution. 

In 1940, the French Army overemphasized its experiences in WWI and failed to reckon with the revolution in military affairs brought about by the technology that allowed mechanization. Clausewitz shows us that socio-political changes may change the face of war as radically as any technology and either towards a more limited or more absolute form. The challenge for both policymakers and practitioners is to identify the “spirit of the age” understand how and to what extent the present socio-political environment constrains war.