War has been defined, A contest between nations and states carried on by force. But this definition is by some considered defective, inasmuch as it would exclude all civil wars.

When war is commenced by attacking a nation in peace, it is called offensive, and when undertaken to repel invasion, or the attacks of an enemy, it is called defensive. A war may be essentially defensive even where we begin it, if intended to prevent an attack or invasion which is under preparation. Besides this general division of war, military writers have made numerous others, such as--

Wars of intervention, in which one state interferes in favor of another. This intervention may either have respect to the internal or to the external affairs of a nation The interference of Russia in the affairs of Poland, of England in the government of India, Austria and the allied powers in the affairs of France during the Revolution and under the empire, are examples under the first head. The intervention of the Elector Maurice of Saxony against Charles V., of King William against Louis XIV., in 1688, of Russia and France in the seven years war, of Russia again between France and Austria, in 1805, and between France and Prussia, in 1806, are examples under the second head Most liberal publicists consider intervention in the internal affairs of nations as indefensible; but the principle is supported by the advocates of the old monarchies of Europe.

Wars of insurrection to gain or to regain liberty; as was the case with the Americans in 1776, and the modern Greeks in 1821.

Wars of independence from foreign dictation and control, as the wars of Poland against Russia, of the Netherlands against Spain, of France against the several coalitions of the allied powers, of the Spanish Peninsula against France, and of China and. India against England. The American war of 1812 partook largely of this character, and some judicious historians have denominated it the war of Independence, as distinguished from the war of the Revolution.

Wars of opinion, like those which the Vendeans have sustained in support of the Bourbons, and those France has sustained against the allies, as also those of propagandism, waged against the smaller European states by the republican hordes of the French Revolution. To this class also belong--

Religious wars, like those of Islamism, of the crusades, and of the Reformation.

Wars of conquest, like those of the Romans in Gaul, of the English in India, of the French in Egypt and Africa, and of the Russians in Circassia.

National wars, in which the great body of the people of a state engage, like those of the Swiss against Austria and the Duke of Burgundy, of the Catalans in 1712, of the Americans against England, of the Dutch against Phillip II., and of the Poles and Circassians against Russia.

Civil wars, where one portion of the state fights against the other, as the war of the Roses in England, of the league in France, of the Guelphs and Ghibelines in Italy, and of the factions in Mexico and South America.

It is not the present intention to enter into any discussion of these different kinds of war, but rather to consider the general subject, and to discuss such general principles and rules as may be applicable to all wars.

War in its most extensive sense may be regarded both as a science and an art. It is a science so far as it investigates general principles and institutes an analysis of military operations; and an art when considered with reference to the practical rules for conducting campaigns, sieges, battles, &c. So is engineering a science so far as it investigates the general principles of fortification, and also artillery, in analyzing the principles of gunnery; but both are arts when considered with reference to the practical rules for the construction, attack, and defence of forts, or for the use of cannon.

This distinction has not always been observed by writers on this subject, and some have asserted that strategy is the science, and tactics the art of war. This is evidently mistaking the general distinction between science, which investigates principles, and art, which forms practical rules.

In popular language, however, it is usual to speak of the military art when we refer to the general subject of war, and of the military sciences when we wish to call attention more particularly to the scientific principles upon which the art is founded. We shall here consider the military art in this general sense, as including the entire subject of war.

As thus defined, the military art may be divided into four distinct branches, viz.: 1st. Strategy; 2d. Fortification, or Engineering; 3d. Logistics; 4th. Tactics. Several general treatises on this art add another branch, called The Policy of War, or the relations of war with the affairs of state.

Strategy is defined to be the art of directing masses on decisive points, or the hostile movements of armies beyond the range of each other's cannon. Engineering embraces all dispositions made to enable troops to resist a superior force the longest time possible; and also the means resorted to by the opposing army to overcome these material obstacles. Logistics embraces the practical details of moving and supplying armies. Tactics is the art of bringing troops into action, or of moving them in the presence of an enemy, that is, within his view, and within the reach of his artillery. All these are most intimately connected. A fault in tactics may occasion the loss of strategic lines; the best combined manoeuvres on the field of battle may lead to no decisive results, when the position, or the direction of the operation is not strategic; sometimes not only battles, but entire campaigns, are lost through neglect of the engineer's art, or faults in his dispositions; again, armies would be of little use without the requisite means of locomotion and of subsistence.

I. Strategy regards the theatre of war, rather than the field of battle. It selects the important points in this theatre, 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 are 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 Cannae, 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 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.

The first point to be attended to in a plan of military operation is to select a good base. Many circumstances influence this selection, such as mountains, rivers, roads, forests, cities, fortifications, military depots, means of subsistence, &c. If the frontier of a state contain strong natural or artificial barriers, it may serve not only as a good base for offensive operations, but also as an excellent line of defence against invasion. A single frontier line may, however, be penetrated by the enemy, and in that case a second or third base further in the interior becomes indispensable for a good defence.

A French army carrying on military operations against Germany would make the Rhine its first base; but if driven from this it would form a second base on the Meuse or Moselle, a third on the Seine, and a fourth on the Loire; or, when driven from the first base, it would take others perpendicular to the front of defence, either to the right, on Befort and Besancon, or to the left, on Mezieres and Sedan. If acting offensively against Prussia and Russia, the Rhine and the Main would form the first base, the Elbe and the Oder the second, the Vistula the third, the Nieman the fourth, and the Dwina and the Dnieper the fifth.

A French army operating against Spain would have the Pyrenees for its first base; the line of the Ebro for a second, resting its wings on the gulf of Gascony and the Mediterranean. If from this position it advance its left, possessing itself of the kingdom of Valencia, the line of the Sierra d'estellas becomes its third base of operations against the centre of Spain.

A base may be parallel, oblique, or perpendicular to our line of operations, or to the enemy's line of defence. Some prefer one plan and some another; the best authorities, however, think the oblique or perpendicular more advantageous than the parallel; but we are not often at liberty to choose between these, for other considerations usually determine the selection.

In 1806, the French forces first moved perpendicular to their base on the Main, but afterwards effected a change of front, and moved on a line oblique or nearly parallel to this base. They had pursued the same plan of operations in the Seven Years War. The Russians, in 1812, based perpendicularly on the Oka and the Kalouga, and extended their flank march on Wiozma and Krasnoi; in 1813, the allies, based perpendicularly on Bohemia, succeeded in paralyzing Napoleon's on the Elbe.

An American army moving by Lake Champlain, would be based perpendicular on the great line of communication between Boston and Buffalo; if moving from the New England states on Quebec and Montreal, the line of operations would be oblique; and if moving from the Niagara frontier by Lake Ontario and the St. Lawrence, the line would be nearly parallel both to our base and to the enemy's line of defence — an operation, under the circumstances, exceedingly objectionable.

Any point in the theatre of operations which gives to the possessor an advantage over his opponent, is regarded as strategic. Their geographical position and political and military character, give them a greater or less influence in directing the campaign. These points are occupied by the defensive army, and attacked by the offensive; if on or near the base, they become the key points for the former, and the objective points for the latter.

It may be well to remark that a strategic point is not necessarily a geometrical point; an entire province, or a considerable portion of a geographical frontier, is, in military language, sometimes denominated a point. In the same way, strategic lines, instead of being mathematical lines, are frequently many miles in width.

The first object of the French in attacking Belgium, is to gain possession of the Mouse, as this position would give them a decided advantage in any ulterior operations. In attacking southern Germany, the course of the Danube offers a series of points which exercise an important influence on the war. For northern Germany, Leipsic and the country bordering on the Saale and the Elbe, are objects often fiercely contested by the French and other belligerent powers. In a war between this country and England, Montreal and the points on the St. Lawrence between Montreal and Quebec, would become objects of the highest importance, and their possession would probably determine the result of the war.

The capital of a state, from its political importance as well as its military influence, is almost always a decisive strategic point, and its capture is therefore frequently the object of an entire campaign. The possession of Genoa, Turin, Alexandria, Milan, &c., in 1796, both from their political and military importance, had a decided influence upon the results of the war in these several states. In the same way Venice, Rome, and Naples, in 1797, Vienna, in the campaigns of 1805 and 1809, Berlin, in 1806, Madrid, in 1808, and Paris, in 1814 and 1815. If Hannibal had captured the capital immediately after the battle of Cannae, he would thus have destroyed the Roman power. The taking of Washington, in 1814, had little or no influence on the war, for the place was then of no importance in itself, and was a mere nominal capital. It, however, greatly influenced our reputation abroad, and required many brilliant successes to wash the blot from our national escutcheon.

Lines of defence in strategy are either permanent or temporary. The great military frontiers of a state, especially when strengthened by natural and artificial obstacles, such as chains of mountains, rivers, lines of fortresses, &c., are regarded as permanent lines of defence. The Alpine range between France and Piedmont, with its fortified passes; the Rhine, the Oder, and the Elbe, with their strongly-fortified places; the Pyrenees, with Bayonne at one extremity and Perpignon at the other; the triple range of fortresses on the Belgian frontier — are all permanent lines of defence. The St. Lawrence river is a permanent line of defence for Canada; and the line of lake Champlain, the upper St. Lawrence, and the lakes, for the United States.

Temporary lines of defence are such as are taken up merely for the campaign. Napoleon's position in Saxony, in 1813; the line of the allies in Belgium, in 1815; the line of the Marne, in 1814, are examples of temporary lines of defence.

It will be seen from these remarks that lines of defence are not necessarily bases of operation.

Strategic positions are such as are taken up during the operations of a war, either by a corps d'armee or grand detachment, for the purpose of checking or observing an opposing force; they are named thus to distinguish them from tactical positions or fields of battle. The positions of Napoleon at Rivoli, Verona, and Legnano, in 1796 and 1797, to watch the Adige; his positions on the Passarge, in 1807, and in Saxony and Silesia in front of his line of defence, in 1813; and Massena's positions on the Albis, along the Limmat and the Aar, in 1799, are examples under this head.

Before proceeding further it may be well to illustrate the strategic relations of lines and positions by the use of diagrams.

(Fig. 1.) The army at A covers the whole of the ground in rear of the line Dc perpendicular to the line Ab, the position of the enemy being at B.

(Fig. 2.) Aj being equal to Bj, A will still cover every thing in rear of Dc.

(Fig. 3.) If the Army A is obliged to cover the point a, the Army B will cover all the space without the circle whose radius is aB; and of course A continues to cover the point a so long as it remains within this circle aB.

A line of operations embraces that portion of the theatre of war which an army or corps d'armee passes over in attaining its object; the front of operations is the front formed by the army as it advances on this line.

When an army acts as a single mass, without forming independent corps, the line it follows is denominated a simple line of operations.

If two or more corps act in an isolated manner, but against the same opposing force, they are said to follow double or multiple lines.

The lines by which Moreau and Jourdan entered Germany in 1796, were double lines; but Napoleon's advance by Bamberg and Gera, in 1806, although moving in seven distinct corps d'armee, formed but a single line of operations.

Interior lines of operations are those followed by an army which operates between the enemy's lines in such a way as to be able to concentrate his forces on one of these lines before the other can be brought to its assistance. For example, Napoleon's line of operations in 1814, between the Marne and the Seine, where he manoeuvred with so much skill and success against the immensely superior forces of the allies.

Exterior lines present the opposite results; they are those which an army will form in moving on the extremities of the opposing masses. For example, the lines of the Marne and the Seine, followed by the army of Silesia and the grand Austro-Russian army, in the campaign of 1814. Burgoyne's line of operations, in 1777, was double and exterior.

Concentric lines are such as start from distant points, and are directed towards the same object, either in the rear or in advance of their base.

If a mass leaves a single point and separates into several distinct corps, taking divergent directions, it is said to pursue eccentric lines.

Lines are said to be deep, when the end to be attained is very distant from the base.

The lines followed by a secondary or auxiliary force are denominated secondary lines.

The lines pursued by the army of the Sombre-et-Meuse in 1796, and by Bagration in 1812, were secondary lines, as the former were merely secondary to the army of the Rhine, and the latter to that of Barclay.

Accidental lines are those which result from a change in the primitive plan of campaign, which give a new direction to the operations. These are of rare occurrence, but they sometimes lead to important results.

The direction given to a line of operations depends not only on the geographical situation of the country, but also on the positions occupied by the enemy. The general plan of campaign is frequently determined on previous to beginning operations, but the choice of lines and positions must ordinarily result from the ulterior events of the war, and be made by the general as these events occur.

As a general rule, a line of operations should be directed upon the centre, or one of the extremities of the enemy's line of defence; unless our forces be infinitely superior in number, it would be absurd to act against the front and extremities at the same time.

If the configuration of the theatre of operations be favorable to a movement against the extremity of the enemy's line of defence, this direction may be best calculated to lead to important results. (Fig. 4.)

In 1800 the army of the Rhine was directed against the extreme left of the line of the Black Forest; the army of reserve was directed by the St. Bernard and Milan on the extreme right and rear of Melas's line of defence: both operations were most eminently successful. (Fig. 5.)

It may be well to remark that it is not enough merely to gain the extremity and rear of the enemy, for in that case it may be possible for him to throw himself on our communications and place us in the very dilemma in which we had hoped to involve him. To avoid this danger it is necessary to give such a direction to the line of operations that our army shall preserve its communications and be able to reach its base.

Thus, if Napoleon, in 1800, after crossing the Alps, had marched by Turin on Alexandria and received battle at Marengo, without having first secured Lombardy and the left of the Po, his own line of retreat would have been completely cut off by Melas; whereas, by the direction which he gave to his line of operations he had, in case of reverse, every means for reaching either the Var or the Valois. (Fig. 6.) Again, in 1806, if he had marched directly from Gera to Leipsic, he would have been cut off from his base on the Rhine; whereas, by turning from Gera towards Weimar, he not only cut off the Prussians from the Elbe, but at the same time secured to himself the roads of Saalfield, Schleitz, and Hoff, thus rendering perfectly safe his communications in his rear. (Fig. 7.)

We have said that the configuration of the ground and the position of the hostile forces may sometimes render it advisable to direct our line of operations against the extremity of the enemy's line of defence; but, as a general rule, a central direction will lead to more important results. This severs the enemy's means of resistance, and enables the assailant to strike, with the mass of his force, upon the dissevered and partially paralyzed members of the hostile body. (Fig. 8.)

Such a plan of operations enabled Napoleon, in the Italian campaigns of 1796 and 1797, to pierce and destroy, with a small force, the large and successive armies which Austria sent against him. In 1805 his operations were both interior and central: in 1808 they were most eminently central: in 1809, by the central operations in the vicinity of Ratisbonne, he defeated the large and almost victorious army of the Archduke Charles: in 1814, from his central position between the Marne and Seine, with only seventy thousand men against a force of more than two hundred thousand, he gained numerous victories, and barely failed of complete success. Again in 1815, with an army of only one hundred and twenty thousand men against an allied force of two hundred and twenty thousand, by his central advance on Charleroi and Ligny, he gained a most decided advantage over the enemy — an advantage lost by the eccentric movement of Grouchy: and even in 1813, his central position at Dresden would have secured him most decisive advantages, had not the faults of his lieutenants lost these advantages in the disasters of Kulm and the Rosbach.

For the same frontier it is objectionable to form more than one army; grand detachments and corps of observation may frequently be used with advantage, but double or multiple lines of operation are far less favorable than one simple line. It may however sometimes occur that the position of the enemy's forces will be such as to make this operation the preferable one. In that case, interior lines should always be adopted, unless we have a vast superiority in number. Double exterior lines, with corps several days' march asunder, must be fatal, if the enemy, whether acting on single or double interior lines, take advantage of his position to concentrate his masses successively against our isolated forces. The Roman armies under the consuls Flaminius and Servilius opposed Hannibal on exterior lines, the one by Florence and Arrezzio, and the other by Modena and Ariminum. Hannibal turned the position of Flaminius and attacked the Roman armies separately, gaining a complete and decisive victory. Such also was the character of the operations of the French in 1795, under Pichegru and Jourdan; they met with a bloody and decisive defeat. Again in 1796, the French armies under Jourdan and Moreau, pursued exterior lines; the Archduke Charles, from his interior position, succeeded in defeating both the opposing generals, and forcing them to retreat. If the two armies united had pursued a single line, the republican flag had been carried in triumph to Vienna.

Converging lines of operation are preferable, under most circumstances, to diverging lines. Care should be taken, however, that the point of meeting be such that it may not be taken as a strategic position by the enemy, and our own forces be destroyed in detail, before they can. effect a junction. In 1797 the main body of the Austrians, under Alvinzi, advanced against Napoleon, on three separate lines, intending to concentrate at Rivoli, and then attack the French in mass; but Napoleon took his strategic position at Rivoli, and overthrew the enemy's corps as they successively appeared. In the same way the Archduke Charles took an interior position, between Moreau and Jourdan, in 1796, and prevented them from concentrating their forces on a single point. Wurmser and Quasdanowich attempted to concentrate their forces on the Mincio, by moving on the opposite shores of Lake Garda; but Napoleon took an interior position and destroyed them. In 1815 Blucher and Wellington, from their interior position, prevented the junction of

Diverging lines may be employed with advantage against an enemy immediately after a successful battle or strategic manoeuvre; for by this means we separate the enemy's forces, and disperse them; and if occasion should require it, may again concentrate our forces by converging lines. Such was the manoeuvre of Frederick the Great, in 1757, which produced the battles of Rosbach and Leuthen; such also was the manoeuvre of Napoleon at Donawert in 1805, at Jena in 1806, and at Ratisbon in 1809.

Interior lines of operations, when properly conducted, have almost invariably led to success: indeed every instance of failure may be clearly traced to great unskilfulness in their execution, or to other extraneous circumstances of the campaign. There may, however, be cases where it will be preferable to direct our forces on the enemy's flank; the geographical character of the theatre of war, the position of other collateral forces, &c., rendering such a direction necessary. But as a general rule, interior and central lines, for an army of moderate forces, will lead to decisive results.

Napoleon's Italian campaigns in 1796 and 1797, the campaign of the Archduke Charles in 1796, Napoleon's campaigns of 1805 and 1809 against Austria, and of 1806 and 1807 against Prussia and Russia, of 1808 in Spain, his manoeuvres in 1814, between the battle of Brienne and that of Paris, and his operations previous to the battle of Ligny in 1815, are all brilliant examples under this head.

To change the line of operations, in the middle of a campaign, and follow accidental lines, is always a delicate affair, and can only be resorted to by a general of great skill, and with disciplined troops. In such a case it may be attended with important results. It was one of Napoleon's maxims, that a line of operations, when once chosen, should never be abandoned. This maxim, however, must sometimes be disregarded by an army of undisciplined troops, in order to avoid entire destruction; but the total abandonment of a line of operations is always attended with great loss, and should be regarded as a mere choice of evils. A regular army can always avoid this result, by changing the direction of its line; thus frequently gaining superior advantages in the new theatre of action. If the plan of this change be the result of a good coup d'oeil, and it be skilfully executed, the rear of the operating army will be secure from the enemy; and moreover, he will be left in doubt respecting its weak points. But such is the uncertainty of this manoeuvre, that it is very rarely taken by the best troops, unless actually forced upon them. If the army be of incongruous materials, generally a change of direction will be less advantageous than to entirely abandon the line, and save as many as possible of the troops for some new plan of operations. (Maxim 20.) If, however, the undisciplined army be sustained by fortifications, it can take up the accidental line of operations in the same manner, and with the same probability of success, as is done by a regular force.

We have examples of accidental lines in the operations of the king of Prussia, after the battle of Hohenkirchen, and of Washington, in New-Jersey, after the action of Princeton. This is one of the finest in military history. Napoleon had projected a change in his line of operations, in case he lost the battle of Austerlitz; but victory rendered its execution unnecessary. Again in 1814 he had planned an entire change of operations; but the want of co-operation of the forces under Mortier and Marmont forced him to abandon a plan which, if properly executed, had probably defeated the allies. Jomini pronounced it one of the most brilliant of his military career.

Having explained the principal terms used in strategy, let us trace out the successive operations of war in their usual strategic relations.

We will suppose war to be declared, and the army to be just entering upon a campaign. The political and military authorities of the state determine upon the nature of the war, and select the theatre of its enterprises. The chief selects certain points, on or near the borders of the seat of war, where his troops are to be assembled, and his materiel collected. These points, together, form his base of operations. He now selects some point, within the theatre of the war, as the first object of his enterprises, and chooses the line of operations most advantageous for reaching this objective point. The temporary positions taken on this line become strategic positions, and the line in his rear, a line of defence. When he arrives in the vicinity of his first object, and the enemy begins to oppose his enterprises, he must force this enemy to retreat, either by an attack or by manoeuvres. For this purpose he temporarily adopts certain lines of manoeuvre, which may deviate from his general line of operations. The ulterior events of the campaign may possibly cause him to make these new, or accidental lines, his lines of operations, The approach of hostile forces may cause him to detach secondary corps on secondary lines; or to divide his army, and pursue double or multiple lines. The primitive object may also be relinquished, and new ones proposed, with new lines and new plans of operations. As he advances far from his primitive base, he forms new depots and lines of magazines. He may encounter natural and artificial obstacles. To cross large rivers in the face of an enemy is a hazardous operation; and he requires all the art of the engineer in constructing bridges, and securing a safe passage for his army. If a fortified place is to be taken, he will detach a siege corps, and either continue his march with the main army, or take a strategic position to cover this siege. Thus Napoleon, in 1796, with an army of only 50,000 combatants, could not venture to penetrate into Austria, with Mantua and its garrison of 25,000 men in his rear, and an Austrian force of 40,000 before him. But in 1806 the great superiority of his army enabled him to detach forces to besiege the principal fortresses of Silesia, and still to continue his operations with his principal forces. The chief of the army may meet the enemy under circumstances such as to induce or compel him to give battle. If he should be victorious, the enemy must be pursued and harassed to the uttermost. If he should be defeated, he must form the best plan, and provide the best means of retreat. If possible, he must take shelter in some line of fortifications, and prepare to resume the offensive. Lines of retrenchment and temporary works may sometimes serve him as a sufficient protection. Finally, when the unfavorable season compels him to suspend his operations, he will go into winter cantonments, and prepare for a new campaign.

Such are the ordinary operations of war: its relations to strategy must be evident, even to the most superficial reader.

Not unfrequently the results of a campaign depend more upon the strategic operations of an army, than upon its victories gained in actual combat. Tactics, or movements within the range of the enemy's cannon, is therefore subordinate to the choice of positions: if the field of battle be properly chosen, success will be decisive, and the loss of the battle not disastrous; whereas, if selected without reference to the principles of the science, the victory, if gained, might be barren, and defeat, if suffered, totally fatal: thus demonstrating the truth of Napoleon's maxim, that success is oftener due to the genius of the general, and to the nature of the theatre of war, than to the number and bravery of the soldiers. (Maxim 17, 18.)

We have a striking illustration of this in the French army of the Danube, which, from the left wing of General Kray, marched rapidly through Switzerland to the right extremity of the Austrian line, and by this movement alone conquered all the country between the Rhine and Danube without pulling a trigger.

Again, in 1805, the army of Mack was completely paralyzed, and the main body forced to surrender, at Ulm, without a single important battle. In 1806, the Prussians were essentially defeated even before the battle of Jena. The operations about Heilesberg, in 1807, the advance upon Madrid, in 1808, the manoeuvres about Ratisbon, in 1809, the operations of the French in 1814, and the first part of the campaign of 1815, against vastly superior numbers, are all familiar proofs of the truth of the maxim.

Strategy may therefore be regarded as the most important, though least understood, of all the branches of the military art.

Strategy may be learned from didactic works or from general military histories. There are very few good elementary works on this branch of the military art. The general treatises of the Archduke Charles, and of General Wagner, in German, (the former has been translated into French,) are considered as the best. The discussions of Jomini on this subject in his great work on the military art, are exceedingly valuable; also the writings of Rocquancourt, Jacquinot de Presle, and Gay de Vernon. The last of these has been translated into English, but the translation is exceedingly inaccurate. The military histories of Lloyd, Templehoff, Jomini, the Archduke Charles, Grimoard, Gravert, Souchet, St. Cyr, Beauvais, Laverne, Stutterheim, Wagner, Kausler, Gourgaud and Montholon, Foy, Mathieu Dumas, Segur, Pelet, Koch, Clausewitz, and Thiers, may be read with great advantage. Napier's History of the Peninsular War is the only English History that is of any value as a military work: it is a most excellent book. Alison's great is utterly worthless to the military man; the author is ignorant of the first principles of the military art, and nearly every page is filled with the grossest blunders.

We subjoin the titles of a few of the best works that treat of strategy, either directly or in connection with military history. par le Prince Charles, traduit de l'allemand, 3 vols. in 8vo. This is a work of great merit. The technical terms, however, are very loosely employed. par le Baron Jomini. His chapter on strategy embodies the principles of this branch of the art. Von Wagner. par Rocquancourt. This work contains much valuable information connected with the history of the art of war; but it is far too diffuse and ill-arranged for an elementary book. par Jacquinot de Presle. This work is especially designed for cavalry officers, and the other branches of military service are but very briefly discussed. De Vernon's Treatise on the Science of War and Fortification contains much valuable information; but, as an elementary book, it has the same objections as that of Rocquancourt. by Lloyd and Templehoff. The military writings of Lloyd and Templehoff are valuable as connected with the history of strategy; but many of the principles laid down by these writers are now regarded as erroneous. , as dictated by himself to Gourgaud and Montholon, have been translated into English. It is hardly necessary to remark that they contain all the general principles of military art and science. No military man should fail to study them thoroughly. The matter is so condensed, and important principles are embodied in so few words, that they are not easily understood by the ordinary reader, and probably will never be popular with the multitude. par Guibert. A work very popular in its day, but now far less valuable than the writings already mentioned. von Gravert. Regarded by military men as a valuable historical fragment. Souchet. de Gouvion St. Cyr. par Reveroni St. Cyr. par Grimoard. Beauvais. Laverne. Foy. Mathieu Dumas. . Segur , Pelet. Koch. Clausewitz. Thiers. Vaudoncourt. Vaudoncourt. Vaudoncourt. Vaudoncourt. Carion-Nisas. Chambray. John Jones. Napier. Armstrong.

All the above are works of merit; but none are more valuable to the military man than the military histories of Jomini and Kausler, with their splendid diagrams and maps.