The nature of the things does not allow of a completely satisfactory definition of these three factors, denoting respectively, space, mass, and time in war; but that we may not sometimes be quite misunderstood, we must try to make somewhat plainer the usual meaning of these terms, to which we shall in most cases adhere.
1.—Theatre of War.
This term denotes properly such a portion of the space over which war prevails as has its boundaries protected, and thus possesses a kind of independence. This protection may consist in fortresses, or important natural obstacles presented by the country, or even in its being separated by a considerable distance from the rest of the space embraced in the war.—Such a portion is not a mere piece of the whole, but a small whole complete in itself; and consequently it is more or less in such a condition that changes which take place at other points in the seat of war have only an indirect and no direct influence upon it. To give an adequate idea of this, we may suppose that on this portion an advance is made, whilst in another quarter a retreat is taking place, or that upon the one an army is acting defensively, whilst an offensive is being carried on upon the other. Such a clearly defined idea as this is not capable of universal application; it is here used merely to indicate the line of distinction.
2.—Army.
With the assistance of the conception of a Theatre of War, it is very easy to say what an Army is: it is, in point of fact, the mass of troops in the