The essence of every profession is expressed in the writings of its unifying theorists: Freud for psychology, Adam Smith on economics, Justice Marshall on law, and — depending on one's preferences — Marx or Jefferson on governance. War is no exception. The 19th-century Prussian writer Carl von Clausewitz is regarded as a prophet whose views on the character and nature of war have held up best over the past two centuries.

http://www.armedforcesjournal.com/2006/07/1866019