Elements of Military Art and Science / Or, Course Of Instruction In Strategy, Fortification, Tactics Of Battles, &C.; Embracing The Duties Of Staff, Infantry, Cavalry, Artillery, And Engineers; Adapted To The Use Of Volunteers And Militia; Third Edition; With Critical Notes On The Mexican And Crimean Wars.

by H. W. Halleck

"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 of finding security only in flight; instead of habitually refusing to look the enemy in the face; instead of leaving his march undisturbed; instead of abandoning, without contest, points strong by nature or by art;—instead of all this, the true war of defence seeks every occasion to meet the enemy, and loses none by which it can annoy or defeat him; it is always awake; it is constantly in motion, and never unprepared for either attack or defence. When not employed in efforts of courage or address, it incessantly yields itself to those of labor and science. In its front it breaks up roads or breaks down bridges; while it erects or repairs those in its rear: it forms abbatis, raises batteries, fortifies passes, or intrenches encampments; and to the system of deprivation adds all the activity, stratagem, and boldness of la petite guerre. Dividing itself into detachments, it multiplies its own attacks and the alarms of the enemy. Collecting itself at a single point, it obstructs his progress for days, and sometimes for weeks together. Does it even abandon the avenues it is destined to defend? It is but for the purpose of shielding them more securely, by the attack of his hospitals, magazines, convoys, or reinforcements. In a word, by adopting the maxim, that the enemy must be made to pay for whatever he gains, it disputes with him every inch of ground, and if at last it yields to him a victory, it is of that kind which calls forth only his sighs."

In discussing the subject of strategy, certain technical terms are employed, such as theatre of war; theatre of operations; base of operations, or the line from which operations start; objective points, or points to which the operations are directed; line of operations, or the line along which an army moves; key points, or points which it is important for the defensive army to secure; line of defence, or the line which it is important to defend at all hazards: and in general, strategic points, strategic lines, strategic positions, &c. As these terms are very generally used in military books, it may be well to make ourselves thoroughly acquainted with their import. After defining these terms and explaining their meaning and application, it is deemed best to illustrate their use by reference to well-known and striking historical examples.

The theatre of a war embraces not only the territory of the two belligerent powers, but also that of their allies, and of such secondary powers as, through fear or interest, may be drawn into the contest. With maritime nations it also embraces the seas, and sometimes crosses to another continent. Some of the wars between France and England embraced the two hemispheres.

The theatre of operations, however, is of a more limited character, and should not be confounded with the theatre of war. In general, it includes only the territory which an army seeks, on the one hand, to defend, and on the other, to invade. If two or more armies be directed towards the same object, though by different lines, their combined operations are included in the same theatre but if each acts independently of the others, and seeks distinct and separate objects, each must have its own independent theatre of operations.

A war between France and Austria may embrace all Italy and Germany, but the theatre of operations may be limited to only a portion of these countries. Should the Oregon question lead to hostilities between the United States and England, the theatre of war would embrace the greater part of North America and the two oceans, but the theatre of operations would probably be limited to Canada and our northern frontier, with naval descents upon our maritime cities.