On War ('Vom Kriege) is a book written by 19th Century Prussian military thinker Carl von Clausewitz, published in 1848 and widely regarded as that authors' magnum opus. The book, whilst primarily focused on military strategy, also provides tactical and operational guides and deals with political and economic problems arising from war.
As an officer in the Prussian Army in 1806, Clausewitz had had first had experience of how the forces of the ancien regime had crumbled before the Napoleonic armies, and the issues this raised deeply unsettled the young officer. Though Clausewitz dismissed the war as being a total departure from previous wars, as some claimed, he noted it raised important issues which his book tries to address.
The book is divided into a series of books, each with a specific focus on a set of topics. It is best to consider On War for what is was meant to be - a manual for the Prussian Military Academy - rather than a simple book to be read cover to cover. In order, the books are:
- On the Nature of War
- On the Theory of War
- On Strategy in General
- The Engagement
- Military Forces
- The Attack
- War Plans
Clausewitz makes a large number of "key observations" throughout his work, returning again and again to a number of themes. Broadly, these can be boiled down to a handful of points:
- "War is a continuation of politics by other means" - war is not an end in itself, rather, a means to achieving a political goal by attaining power over another actor.
- There are broadly two types of war "limited war" and "disarming war".
- Theoretically, "total" war is the "ideal" - that is, what war is at it's theoretical purist. However, because of real-world concerns and issues, no war can ever be truly "total". Clausewitz famously warns against thinking like this, stating that "over-exertion can be as dangerous in war as under-exertion. A state that lives beyond it's means in war invites defeat."
There are a number of other ideas that Clausewitz refers to in a more military context. These include, in no special order:
- Fog of War
- The "fascinating trinity" of government, military and people
- The asymmetry of war and, in particular, attack and defence
- Centres of gravity
- That "war" belongs to the social realm, "strategy" to art and "tactics" to science
- Military Genius
- The relationship between politics and the military, especially in terms of objectives