In close combat the essence of defence consists in standing firm, as if rooted to the ground; the essence of the attack is movement. Cavalry is entirely deficient in the first quality; on the other hand, it possesses the latter in an especial manner. It is therefore only suited for attack. Infantry has especially the property of standing firm, but is not altogether without mobility.
From this division of the elementary forces of war into different arms, we have as a result, the superiority and general utility of Infantry as compared with the other two arms, from its being the only arm which unites in itself all the three elementary forces. A further deduction to be drawn is, that the combination of the three arms leads to a more perfect use of the forces, by affording the means of strengthening at pleasure either the one or the other of the principles which are united in an unalterable manner in Infantry.
The destructive principle of fire is in the wars of the present time plainly beyond measure the most effective; nevertheless, the close combat, man to man, is just as plainly to be regarded as the real basis of combat. For that reason, therefore, an army of artillery only would be an absurdity in war, but an army of cavalry is conceivable, only it would possess very little intensity of force An army of infantry alone is not only conceivable but also much the strongest of the three. The three arms, therefore, stand in this order in reference to independent value—Infantry, Cavalry, Artillery.
But this order does not hold good if applied to the relative importance of each arm when they are all three acting in conjunction. As the destructive principle is much more effective than the principle of motion, therefore the complete want of cavalry would weaken an army less than the total want of artillery.
An army consisting of infantry and artillery alone, would certainly find itself in a disagreeable position if opposed to an army composed of all three arms; but if what it lacked in cavalry was compensated for by a proportionate increase of infantry, it would still, by a somewhat different mode of acting, be able to do very well with its tactical economy. Its outpost service would cause some embarrassment; it would never be able to pursue a beaten enemy with great vivacity, and it must make a retreat with greater hardships and efforts; but these inconveniences would still never be sufficient in themselves to drive it completely out of the field.—On the other hand, such an army opposed to one composed of infantry and cavalry only would be able to play a very good part, while it is hardly conceivable that the latter could keep the field at all against an army made up of all three arms.
Of course these reflections on the relative importance of each single arm result only from a consideration of the generality of events in war, where one case compensates another; and therefore it is not our intention to apply the truth thus ascertained to each individual case of a particular combat. A battalion on outpost service or on a retreat may, perhaps, choose to have with it a squadron in preference to a couple of guns. A body of cavalry with horse artillery, sent in rapid pursuit of, or to cut off, a flying enemy wants no infantry, etc., etc.
If we summarise the results of these considerations they amount to this.
1. That infantry is the most independent of the three arms.
2. Artillery is quite wanting in independence.
3. Infantry is the most important in the combination of the three arms.