Carl Philipp Gottfried von Clausewitz died almost 200 years ago, yet he remains one of the most important and influential of all military thinkers. His teachings combined strategy with military knowledge to produce a dialectic approach to the philosophy of warfare, and his work is still widely taught in military academies around the world. There are few senior military leaders anywhere who are not familiar with his seminal book, On War.
In fact, with the exception of Napoleon Bonaparte, no man was more influential on the military tactics and strategy of 19th century warfare than Clausewitz, a Prussian soldier and military theorist who stressed the moral and political aspects of war. On War was mandatory for all military students and officers to read during the 19th century, and it was common practice for generals during the American Civil War to carry Clausewitz’s treatise and read it to assist them in strategy and tactics.
On War covered every conceivable facet of warfare, using historical battles as examples of what to do and what not to do. The treatise discusses how opposite forces interact, and how unexpected new developments unfolding under the "fog of war" called for rapid decisions by alert commanders. In opposition to Antoine-Henri Jomini, he argued war could not be quantified or graphed or reduced to mapwork and graphs.
Perhaps most importantly, Clausewitz realized the correlation between politics and war. Clausewitz had many aphorisms, of which the most famous is, "War is not merely a political act, but also a political instrument, a continuation of political relations, a carrying out of the same by other means.” This view of warfare is still the standard viewpoint of war today. What it is easy to overlook is that when On War was first published, Clausewitz was regarded as a fairly insignificant figure, but in hindsight it’s easy to understand why his concepts have stood the test of time.