Book Review: “On War” by Carl von Clausewitz


As we begin to discuss history and the operational art of war we need to examine Clausewitz.

Carl von Clausewitz was a Prussian general with more than 25 years of experience when he started writing “On War.” He was a veteran of the Napoleonic Wars (1803–1815), a series of wars that was sparked by the French Revolution of 1789.

General Carl von Clausewitz

These wars revolutionized European armies. Over the 12 years new and complex ideas played out on an unprecedented scale, mainly owing to the application of modern mass conscription.

Napoleon was responsible for much of this innovation. He created a highly mobile army. He outfitted a well-armed artillery force. He gave artillery increased tactical importance.

Rather than relying on infantry to wear away the enemy’s defenses with men dying in linear columns, he massed his artillery as a spearhead to pound a break in the enemy’s line. Once that was achieved, he sent in infantry and cavalry to kill the survivors.

These tactics forever changed the way of war. Historians argue over Napoleon’s influence, but in more than 60 battles, he only lost seven, mostly at the end of his career. His enemies adopted his tactics. One of these was Clausewitz.


Clausewitz, was captured by the French at a young age. As an officer, he was given the opportunity to tour France. He was intrigued by the manner in which the leaders of the French Revolution, especially Napoleon, had changed the conduct of war.

Their ability to motivate the populace and to gain access to the full resources of the state. He realized this was unleashing war on a greater scale than had previously been seen in Europe.

His insights he gained from his political and military experiences. He was a professional soldier who spent a considerable part of his life fighting against Napoleon. All this combined with a solid grasp of European history, provided the basis for his book.

The Book

The book contains a wealth of historical examples used to illustrate its various concepts based directly on the man who had become a soldier at 12, and his baptism of fire at 13.

Israeli military historian Azar Gat writes, “the ‘general message’ of the book was that “the conduct of war could not be reduced to universal principles.”

Among many strands of thought, three stand out as essential to Clausewitz’s concept:

  • War must never be seen as having any purpose in itself, but should be seen as an instrument of “Politik” – a German word that conflates the meanings of the English words policy and politics: “War is not merely a political act, but also a real political instrument, a continuation of political commerce, a carrying out of the same by other means.”


  • The military objectives in war that support one’s political objectives fall into two broad types: “war to achieve limited aims” and war to “disarm” the enemy: “to render [him] politically helpless or militarily impotent.”


  • All else being equal, the course of war, will tend to favor the party with the stronger emotional and political motivations, but especially the defender (contrary to the common prejudice that soldiers generally endorse aggressive warfare).


Role of Theory

Clausewitz thought of war as a complex phenomenon. The one thing theory does is to allow you to peel those concepts apart. He wrote, “Clarify concepts and idea that have become, as it were, confused and entangled.”

Clausewitz saw his book as a critical exercise about all aspects of war. His writing was a way for him to organize his thoughts on the wonder of how wars were fought and why. He wrote, “…illuminate all phases of war in a through critical inquiry.”

He wanted his book to be a tool to educate the mind of a future military commander. He knew that you didn’t want to enter into a war and to be starting with everything from the beginning to be new.

He wanted his book to be used a checklist to have everything lined up to understand the concept and nature of war before you embark on a campaign. His ideas were meant to be used as part of the education in the development of the mind of the commander.

He cautioned, “… theory is not something you take the battlefield.” He uses an analogy of taking your teacher with you once you leave the classroom. He says you don’t take theory with you once you are on the battlefield.

He lets his readers know that education of war is to prepare leaders and commanders for by studying the theory of war.

Key Ideas

Woven throughout his work he states is that war is an instrument of policy. In short, wars are fought for political ends.

He writes, “… war is an act of force to compel our enemy to do our will.” He saw war as an active force. He saw the use of military force to compel your adversary to do what you want him to do.

He believed that the whole purpose was about fighting. You train, arm and equip soldiers to put him in the right place and right place on the battlefield- he wrote this was the only reason that a standing army exists.

Battle is the decisive means in war. In eighteenth century warfare was a lot about maneuver. You move your army to a point of strategic advantage (the high ground).

You don’t maneuver for the sake of maneuver. You maneuver to get to a strategic position of advantage so you can defeat the enemy in battle.

He introduced the ideas of friction and fog in war, together bring both chance and uncertainty into play. You can’t account for friction. It just occurs. It’s everything from a fuel tank that leaks to weather conditions. All these have an interplay that causes the friction that leads to uncertainty, both good and bad.

Clausewitz points out that the good commander understands that and accounts for it. By lubricating friction by being flexible and resilient in the face of friction has the will to see through the fog of war to grab the dim in pursuit are the commanders that will win.

He points out the dominance of “psychological forces and effects.” War is not simply about lines on a map or large block charts. There is “a continuous interaction of opposites.” Your adversary is a living, thinking being just like you are. In short, the enemy always has a vote.

War as a Paradoxical Trinity

Some historians think that Clausewitz was writing about three factors that contribute to war: the people, the government and the army. He wrote about connections between the three. He wrote about, “primordial violence, hatred and enmity.” If left unchecked, will take you to absolute, senseless war.

He says war is connected to policy and reason. War is subordinate to policy. You have a triangle of reason, violence all carried out in a backdrop that is characterized by fog and friction. All three have to be kept in balance and in a subordinate relationship.

He wrote, “Our task, therefore, is to develop a theory that maintains a balance between these three tendencies, like an object suspended between three magnets.”

Final Thoughts

Clausewitz writes to ask us a question, “How much is the military profession a thinking profession?” Clausewitz goal throughout his work is to get the military professional to think before they act.

He wants the reader to think about the phenomenon of war, to weave and think throughout before, during and after. His goal is to have the military professional reach a form of enlightenment as they go along. His book is his attempt to professionalize the profession of arms. It is a classic.

Clausewitz Theory of War