Elements of Military Art and Science. H. W. Halleck
and the lines of communication by which they may be reached; it forms the plan and arranges the general operations of a campaign; but it leaves it to the engineers to overcome material obstacles and to erect new ones; it leaves to logistics the means of supporting armies and of moving them on the chosen lines; and to tactics, the particular dispositions for battle, when the armies have reached the destined points. It is well to keep in mind these distinctions, which may be rendered still more obvious by a few illustrations. The point where several lines of communications either intersect or meet, and the centre of an arc which is occupied by the enemy, are strategic points; but tactics would reject a position equally accessible on all sides, especially with its flanks exposed to attack. Sempronius at Trebbia and Varro at Cannæ, so placed their armies that the Carthagenians attacked them, at the same time, in front, on the flanks, and in rear; the Roman consuls were defeated: but the central strategic position of Napoleon at Rivoli was eminently successful. At the battle of Austerlitz the allies had projected a strategic movement to their left, in order to cut off Napoleon's right from Vienna; Weyrother afterwards changed his plans, and executed a corresponding tactical movement. By the former there had been some chance of success, but the latter exposed him to inevitable destruction. The little fort of Koenigsten, from its advantageous position, was more useful to the French, in 1813, than the vast works of Dresden. The little fort of Bard, with its handful of men, was near defeating the operations of Napoleon in 1800, by holding in check his entire army; whereas, on the other hand, the ill-advised lines of Ticino, in 1706, caused an army of 78,000 French to be defeated by only 40,000 men under Prince Eugene of Savoy.
War, as has already been said, may be either offensive or defensive. If the attacking army be directed against an entire state, it becomes a war of invasion. If only a province, or a military position, or an army, be attacked, it is simply regarded as taking the initiative in offensive movements.
Offensive war is ordinarily most advantageous in its moral and political influence. It is waged on a foreign soil, and therefore spares the country of the attacking force; it augments its own resources at the same time that it diminishes those of the enemy; it adds to the moral courage of its own army, while it disheartens its opponents. A war of invasion may, however, have also its disadvantages. Its lines of operation may become too deep, which is always hazardous in an enemy's country. All the natural and artificial obstacles, such as mountains, rivers, defiles, fortifications, &c., are favorable for defence, but difficult to be overcome by the invader. The local authorities and inhabitants oppose, instead of facilitating his operations; and if patriotism animate the defensive army to fight for the independence of its threatened country, the war may become long and bloody. But if a political diversion be made in favor of the invading force, and its operations be attended with success, it strikes the enemy at the heart, paralyzes all his military energies, and deprives him of his military resources, thus promptly terminating the contest. Regarded simply as the initiative of movements, the offensive is almost always the preferable one, as it enables the general to choose his lines for moving and concentrating his masses on the decisive point.
The first and most important rule in offensive war is, to keep your forces as much concentrated as possible. This will not only prevent misfortune, but secure victory—since, by its necessary operation, you possess the power of throwing your whole force upon any exposed point of your enemy's position.
To this general rule some writers have laid down the following exceptions:—
1st. When the food and forage of the neighborhood in which you act have been exhausted and destroyed, and your magazines are, from any cause, unable to supply the deficiency, one of two things must be done; either you must go to places where these articles abound, or you must draw from them your supplies by detachments. The former is rarely compatible with your plan, and necessarily retards its execution; and hence the preference which is generally given to the latter.
2d. When reinforcements are about to join you, and this can only be effected by a march through a country actually occupied by hostile corps, or liable to be so occupied, you must again waive the general rule, and risk one party for the security of the other; or, (which may be better,) make such movements with your main body as shall accomplish your object.
3d. When you have complete evidence of the actual, or probable insurrection in your favor, of a town or province of your enemy, or of a division of his army, you must support this inclination by strong detachments, or by movements of your main body. Napoleon's operations in Italy, in 1796–7, furnish examples of what is here meant.
4th. When, by dispatching a detachment, you may be able to intercept a convoy, or reinforcement, coming to the aid of your enemy.
These are apparent rather than real exceptions to the rule of concentration. This rule does not require that all the army should occupy the same position. Far from it. Concentration requires the main body to be in immediate and supporting reach: small detachments, for temporary and important objects, like those mentioned, are perfectly legitimate, and in accordance with correct principles. Napoleon's position in Spain will serve as an illustration. A hand, placed on the map of that country, will represent the position of the invading forces. When opened, the fingers will represent the several detachments, thrown out on important strategic lines, and which could readily be drawn in, as in closing the hand, upon the principal and central mass, preparatory to striking some important blow.
"If, as we have seen, it be the first great rule for an army acting on the offensive principle, to keep its forces concentrated, it is, no doubt, the second, to keep them fully employed. Is it your intention to seize a particular province of your enemy? to penetrate to his capital? or to cut him off from his supplies? Whatever measure be necessary to open your route to these objects must be promptly taken; and if you mean to subsist yourself at his expense, your movements must be more rapid than his. Give him time to breathe—and above all, give him time to rest, and your project is blasted; his forages will be completed, and his magazines filled and secured. The roads of approach will be obstructed, bridges destroyed, and strong points everywhere taken and defended. You will, in fact, like Burgoyne, in 1777, reduce yourself to the necessity of bleeding at every step, without equivalent or use."
"Such cannot be the fate of a commander who, knowing all the value of acting on the offensive, shakes, by the vigor and address of his first movements, the moral as well as physical force of his enemy—who, selecting his own time, and place, and mode of attack, confounds his antagonist by enterprises equally hardy and unexpected—and who at last leaves to him only the alternative of resistance without hope, or of flying without resistance."
The British army, in the war of the American Revolution, must have been most wretchedly ignorant of these leading maxims for conducting offensive war. Instead of concentrating their forces on some decisive point, and then destroying the main body of our army by repeated and well-directed blows, they scattered their forces over an immense extent of country, and became too weak to act with decision and effect on any one point. On the other hand, this policy enabled us to call out and discipline our scattered and ill-provided forces.
The main object in defensive war is, to protect the menaced territory, to retard the enemy's progress, to multiply obstacles in his way, to guard the vital points of the country, and—at the favorable moment, when the enemy becomes enfeebled by detachments, losses, privations, and fatigue—to assume the offensive, and drive him from the country. This combination of the defensive and offensive has many advantages. The enemy, being forced to take the defensive in his turn, loses much of the moral superiority due to successful offensive operations. There are numerous instances of this kind of war, "the defensive-offensive," as it is sometimes called, to be found in history. The last four campaigns of Frederick the Great of Prussia, are examples which may serve as models. Wellington played a similar part in the Spanish peninsula.
To merely remain in a defensive attitude, yielding gradually to the advances of the enemy, without any effort to regain such positions or provinces as may have fallen into his power, or to inflict on him some fatal and decisive blow on the first favorable opportunity; such a system is always within the reach of ignorance, stupidity, and cowardice; but such is far from being the true Fabian system of defensive war.
"Instead