This is not an easy book to understand. It takes sustained attention, several readings of the most important parts, guidance from supplementary articles, time and interest. After the required investment, the diligent reader will come to understand Clausewitz's system and the remarkable way that it stills aides in understanding the phenomenon of war. Readers who know of what I speak will agree that the results of the recent NATO war against Serbia over Kosova can be explained very accurately in Clausewitzian terms. Much has been made of the fact that Clausewitz died before he could complete the work. We will never know what added insights the Prussian philosopher may have been able to come up with or the additional nuances that he may have added to the framework that he had established. While true, this attitude detracts from what he was able to accomplish. The only finished portion of the book, Part 1 of Book 1 is also the most important. The rest of Book 1, Book 2, Book 3 and Book 8 (the last) are in Bernard Brodie's words, "pure gold". The other books have relevant information for our times too, but one must shift through much which belongs to the past. Clausewitz's theory of war considered war to be "a remarkable trinity" of rational action (policy), irrational action (passion) and the play of chance (friction versus genius). These three points act as poles above which "theory" itself is suspended like a magnet. Alan D. Beyerchen has pointed out that Clausewitz was talking about a non-linear system in that the course the magnet will take as it hovers above and in and out of the three fields of attraction produces an irreproducible trajectory highly sensitive to the initial conditions which set it in motion. In addition we have other important concepts such as the duel nature of war, the importance and uses of theory, friction, war's psychological element, tactical and strategic centers of gravity, and of course the primacy of policy over purely military concerns in strategic planning. All of these are still of interest today. Not bad for a work that was published initially in 1832! One additional note. I recommend the Everyman's Library Edition of On War. First it is the Michael Howard / Peter Paret translation which is the best in English. Second it contains four interesting and enlightening articles by Howard, Paret and Bernard Brodie and last it is a hard cover book printed and bound in Germany and of excellent quality.