General Guderian read his paper, and proceeded to put it into practice in May 1940; not by a direct attack on allied headquarters which was impracticable, but indirectly dislocating the allied command and paralysing its will, by breaking the front and exploiting the breakthrough by speed and terror. He succeeded with the French, but the British got away by the skin of their teeth, though not through any fault of his. It had to wait for the War in the Gulf in 1991, before what Alexander did at Issus and Arbela was truly recreated. So the ancients have a good deal to teach us, when they speak about what they know. And I repeat that it is the study of the rules of conflict which should form the basis of the true psychology; and perhaps the most urgent question to which psychologists might address themselves is whether it is good people or bad people who are capable of the greater degree of mutual understanding, and who are therefore the better able to organise themselves. This is the question that Tolstoy asks at the end of War and Peace. On the answer to this question our future may well depend. The only better psychology is the psychology of reconciliation, but then that is what this book is all about. However as the Romans said, if you want peace you have at least to understand war, even if you have never taken part in it.
So it is not a matter of surprise that the only textbook on psychology that I have found of any use in practice is Clausewitz's treatise On War. Of course it is much more besides. The early chapters on the nature of force, and the theory and practice of its application, the chapters he revised, are among the most abstract and universal discussions that I have ever read. But it is a textbook on psychology amongst other things, because he discusses with interest how the military mind works.
I accept that the rules of conflict only give insight into the workings of a healthy mind working properly, although that includes working under the…