concentrated, pregnant, and far-reaching thoughts on every subject. Through all these it is, of course, impossible to follow him in any introduction. One can really do no more than urge all to read Clausewitz for themselves, to go to the fountain-head, to the master-work itself. In the short space to which I have restricted myself, I propose, therefore, to concentrate on a few of his leading ideas, reluctantly leaving out many others which are really almost just as good.

Theory and Practice

One of the things for which we are most deeply indebted to Clausewitz is that he has shown us clearly the proper place of theory in relation to practice. "It should educate the mind of the future leader in war, or, rather, guide him in his self-instruction, but not accompany him on to the battlefield; just as a sensible tutor forms and enlightens the opening mind of a youth without therefore keeping him in leading-strings all his life."8 Again, "In real action most men are guided by the tact of judgment, which hits the object more or less accurately, according as they possess more or less genius. This is the way in which all great generals have acted, and therein partly lay their greatness and their genius, in that they always hit upon what was right by this tact. Thus also it will always be in action, and so far this tact is amply sufficient. But when it is a question not of acting one's self, but of convincing others in consultation, then all depends upon clear conceptions and demonstrations and the inherent relations; and so little progress has been made in this respect that most deliberations are merely a contention of words, resting on no firm basis, and ending either in every one retaining his own opinion, or in a compromise from mutual considerations of respect, a middle course really without any value. Clear ideas on these matters are not, therefore, wholly useless."9

How true this is any one will admit who reflects for a moment upon the great diversity of opinions on almost every subject held in our army, just because of this want of a central theory common to all. In the domain of tactics it is evident that this holds good even as in strategy, for a common central theory of war will produce a more or less common way of looking at things, from which results more or less common action towards the attainment of the common object.

Rejection of Set and Geometrical Theories

"It should educate the mind of the future leader in war" is what Clausewitz demands from a useful theory; but he most expressly and unreservedly rejects every attempt at a method "by which definite plans for wars or campaigns are to be given out all ready made as if from a machine."10 He mocks at Bülow's including at first in the one term "base" all sorts of things, like the supply of the army, its reinforcements and equipments, the security of its communications with the home country, and lastly the security of its line of retreat, and then fixing the extent of the base, and finally fixing an angle for the extent of that base: "And all this was done merely to obtain a pure geometrical result utterly useless" (Von Caemmerer).

For the same reason Jomini's principle of the Inner Line does not satisfy him, owing to its mere geometrical nature, although he right willingly acknowledges "that it rests on a sound foundation, on the truth that the combat is the only effectual means in war" (Von Caemmerer). All such attempts at theory seem to him therefore perfectly useless, "because they strive to work with fixed quantities, while in war everything is uncertain, and all considerations must reckon with all kinds of variable quantities; because they only consider material objects, while every action in war is saturated with moral forces and effects; lastly, because they deal only with the action of one party, while war is a constant reciprocal effect of both parties" (Von Caemmerer).

"Pity the warrior," says Clausewitz, "who is contented to crawl about in this beggardom of rules." "Pity the theory which sets itself in opposition to the mind"11 (note, the moral forces).

A Theory to be Practically Useful

Clausewitz insists that a useful theory cannot be more than a thorough knowledge of military history and "reflection upon all the situations in which we can be placed in war." "What genius does must be just the best of all rules, and theory cannot do better than to show just how and why it is so." "It is an analytical investigation of the subject which leads to exact knowledge: and if brought to bear on the results of experience, which in our case would be military history, to a thorough familiarity with it. If theory investigates the subjects which constitute war; if it separates more distinctly that which at first sight seems amalgamated; if it explains fully the properties of the means; if it shows their probable effects; if it makes evident the nature of objects; if it brings to bear all over the field of war the light of essentially critical investigation,​—​then it has fulfilled the chief duties of its province. It becomes then a guide to him who wishes to make himself acquainted with war from books; it lights up the whole road for him, facilitates his progress, educates his judgment, and shields him from error."12

Knowledge must be Thorough

This Clausewitz considers most important. He says that "Knowledge of the conduct of war ... must pass completely into the mind, and almost cease to be something objective." For in war "The moral reaction, the ever-changing form of things makes it necessary for the chief actor to carry in himself the whole mental apparatus of his knowledge, in order that anywhere and at every pulse-beat he may be capable of giving the requisite decision from himself. Knowledge must, by this complete assimilation with his own mind and life, be converted into real power."

So much for Clausewitz, therefore, as the greatest yet the simplest and least theoretical of theorists on war. Mark well his comforting dictum that "Theory is nothing but rational reflection upon all the situations in which we can be placed in war." That is a task which we have all more or less attempted.