The conception of law in relation to perception is not necessary for the conduct of War, because the complex phenomena of War are not so regular, and the regular are not so complex, that we should gain anything more by this conception than by the simple truth. And where a simple conception and language is sufficient, to resort to the complex becomes affected and pedantic. The conception of law in relation to action cannot be used in the theory of the conduct of War, because owing to the variableness and diversity of the phenomena there is in it no determination of such a general nature as to deserve the name of law.
But principles, rules, prescriptions, and methods are conceptions indispensable to a theory of the conduct of War, in so far as that theory leads to positive doctrines, because in doctrines the truth can only crystallise itself in such forms.
As tactics is the branch of the conduct of War in which theory can attain the nearest to positive doctrine, therefore these conceptions will appear in it most frequently.
Not to use cavalry against unbroken infantry except in some case of special emergency, only to use firearms within effective range in the combat, to spare the forces as much as possible for the final struggle—these are tactical principles. None of them can be applied absolutely in every case, but they must always be present to the mind of the Chief, in order that the benefit of the truth contained in them may not be lost in cases where that truth can be of advantage.
If from the unusual cooking by an enemy’s camp his movement is inferred, if the intentional exposure of troops in a combat indicates a false attack, then this way of discerning the truth is called rule, because from a single visible circumstance that conclusion is drawn which corresponds with the same.
If it is a rule to attack the enemy with renewed vigour, as soon as he begins to limber up his artillery in the combat, then on this particular fact depends a course of action which is aimed at the general situation of the enemy as inferred from the above fact, namely, that he is about to give up the fight, that he is commencing to draw off his troops, and is neither capable of making a serious stand while thus drawing off nor of making his retreat gradually in good order.
Regulations and methods bring preparatory theories into the conduct of War, in so far as disciplined troops are inoculated with them as active principles. The whole body of instructions for formations, drill, and field service are regulations and methods: in the drill instructions the first predominate, in the field service instructions the latter. To these things the real conduct of War attaches itself; it takes them over, therefore, as given modes of proceeding, and as such they must appear in the theory of the conduct of War.