On War Book Summary - On War Book explained in key points
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On War summary

Carl von Clausewitz

Observations on the Nature, Theory and Strategy of War and Combat

4.3 (383 ratings)
20 mins

Brief summary

"On War" by Carl von Clausewitz is a classic military strategy book that examines the nature of war and its complexities. Clausewitz stresses the importance of understanding the political motives behind wars and the role of chance in determining outcomes.

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    On War
    Summary of 4 key ideas

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    Key idea 1 of 4

    War is about disarming your opponent through force, and it requires great presence of mind.

    Before we dive into the heady subject of nineteenth-century warfare, let’s take a quick moment to break down the text. Carl von Clausewitz’s On War is divided into four sections. The first deals with establishing an agreed-upon definition for war, the second gets into theory and criticism, while the third and fourth sections touch upon strategy and tactics. So, let’s follow Clausewitz’s lead by looking at four Blink chapters that grab some of the main points from each section.

    The first question is: What is war? The author boils it down to its most basic elements and says that war is essentially a duel that is carried out on a large scale. He also compares it to a wrestling match, in that we have two forces, each attempting to bend the other to its will. The goal for both sides is to reach a point where the other is incapable of fighting any further. More often than not, this means that the goal is to disarm the opponent.

    How is this goal achieved? In one word: violence. These days we have culture wars and information wars, but in the context of the early nineteenth century, the war we’re talking about is by its very nature violent. It uses physical force to achieve its ends. For the most part, we’re still talking about two armies, with columns of soldiers, squaring off against each other on a battlefield.

    Now, this leads us to one of the first of moral quandaries. Every step of the way, the author is interested in exploring the moral issues of war. And right from the get-go, we find ourselves faced with a tricky question. Let’s say that we admit that war is an inescapably violent affair. How violent must it be? Even back then, there were some folks who believed that a war could be decided with a minimum amount of bloodshed. The author, however, isn’t convinced. In fact, he cautions that such an approach would likely backfire. If the goal is the disarmament and bending of your opponent's will, then using your physical power to its utmost extent is the only logical approach. As the author sees it, the idea of moderation in war is absurd.

    Clausewitz continues to define war in other ways. He makes a point of stating that war isn’t a single battle, nor is it an isolated event. For every war, there’s a backstory of events and political decisions that led up to the conflict. Therefore, we can see war as a matter of reciprocal actions. This means that every step of the way, each side is reacting to the other. Each side must make judgments on how best to react. But for the most part, there’ll be an escalation during this process until war is declared and one side is disarmed.

    That said, it’s important to note that the result of a war is never the final word. If you disarm your opponent today, that doesn’t mean they won’t rearm and attack you again tomorrow. In fact, whatever hostility they felt toward you before may be small potatoes compared to the anger they feel after being defeated. This anger and fierce resentment shouldn’t be underestimated, either. Such motivations of spirit can be a deciding factor in an army’s performance.

    This circles back to the author’s insistence that war is a matter of using utmost power. Leaving your opponent well-armed and capable of resuming their attack just doesn’t make sense. This also touches upon another important characteristic of war: the unknown. Some people credit Clausewitz with popularizing the concept of the “fog of war.” Indeed, it’s often the case that neither opponent fully knows the full extent of the other’s armament, their position, or how many soldiers they have in reserve. As a result, commanders are often forced to make decisions with incomplete information. This fact can also be seen to support the idea that one uses their utmost power as a general rule.

    The lack of complete information also plays a large role in determining the qualities that make the best military commanders. What makes someone a military genius? While it should go without saying that a commander be intelligent, and have a keen understanding of human behavior, one must also be able to overcome the physical danger and suffering that goes hand-in-hand with war.

    He describes war as a “great conquest over the unexpected,” and for this reason, he cites courage as a primary quality of a great leader. Courage in the face of physical danger, but also in the face of moral responsibility – in making tough decisions. One must be both firm and resolute, and calm under pressure, but also willing to take quick and bold action when faced with the unexpected.

    In other words, a great commander needs a steady presence of mind. All the qualities of war – the danger, the suffering, the chance, the unknown – these are all things that can lead to a mind being consumed with doubt, which is about the worst thing a military commander can have.

    Leaders also need to grapple with what the author considers the primary “friction” of war, which is that the aims of war are usually simple while achieving those aims is often incredibly difficult. This is one of the last points he makes in the first section. And it's a good note to leave on as we head into the second chapter. In many ways, war is simple. Like a wrestling match. But in other ways, it’s infinitely complex.

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    What is On War about?

    On War (1832) is widely considered to be a landmark book on the subject of war. In its serious and thoughtful consideration of why and how states engage in warfare, it continues to be an influential piece of writing centuries later.

    On War Review

    On War (1832) by Carl von Clausewitz is an insightful exploration of the nature of war and its complexities. Here are three reasons why this book is definitely worth reading:

    • It offers a detailed analysis of the strategic, political, and social aspects of war, providing readers with a comprehensive understanding of the subject.
    • Supported by historical examples, the book illustrates Clausewitz's theories and principles, making it relevant and applicable to both past and present conflicts.
    • The author's thought-provoking ideas challenge conventional wisdom and invite readers to critically assess their own understanding of war, making it a thought-provoking and engaging read.

    Who should read On War?

    • History buffs
    • Those interested in the politics and morality of war
    • Anyone curious about military strategy

    About the Author

    Carl von Clausewitz was a general in the Prussian army who fought in many battles during the Napoleonic Wars, including the Battle of Jena and the Battle of Borodino. Following these experiences, he spent over ten years writing On War. Though it was incomplete at the time of his death in 1831, it was posthumously published by his wife the following year.

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    On War FAQs 

    What is the main message of On War?

    The main message of On War is an examination of the nature and theory of warfare.

    How long does it take to read On War?

    The reading time for On War varies depending on the reader's speed, but it typically takes several hours. However, the Blinkist summary can be read in just a few minutes.

    Is On War a good book? Is it worth reading?

    On War is a compelling book that offers valuable insights into the nature of warfare. It is definitely worth reading.

    Who is the author of On War?

    The author of On War is Carl von Clausewitz.

    What to read after On War?

    If you're wondering what to read next after On War, here are some recommendations we suggest:
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