Diverging or exeentric lines of retreat are eminently wrong. As an instance may be given Wurmser's retreat before Bonaparte. Bona parte having directed his whole force on one division, overthrew it at Trent ; then getting in rear, and on time communications of the other division, destroyed it at l Bassano and Mautua ; he, Bonaparte himself, having by a concentric retreat just previously been enabled to beat Wurmser.
The retreat of the Russian armies in 1812, under Barclay de Tolli and Prince Bagration, before Napoleon, is an example of the gees advantages of concentric retreats. Though Napoleon made repeated attempts to intercept them, he was unable to prevent their retiring on, and joining at, Smolensk°, whence they retired on Moscow ; and though they were beaten at 3loskwa, the battle was not very decisive ; and their armies, by keeping together, were enabled to menace Napo leon's communications. This, according to Jumini, was the commence ment ef Napoleon's disasters.
Concentric lines of retreat require care in using them, that the divi sions joining do not get intermingled, which may lead to inextricable confusion and disaster, as was time case with the Prussians after Jena, by which they suffered a severe augmentation of their disasters. Lastly, when an army employs converging or concentric lines of opera tions, it is necessary to organiso the marches so that the divisions may arrive at their place of assemblemeut before the enemy can reach it, so as to intercept and defeat the divisions separately.
In the campaign of 1809, the British and Spanish armies were com pelled to act un what are called double excentric lines of operations ; for Lord Wellington was on the line of the Tagus, having Lisbon for a base, while Vencgas with a Spanish army was employed in La Mancha; and there were besides the forces in Gallieia and Leon. The armies, being thus separated from each other, were quite unable to co-operate for one object, even had the Spanish generals and armies been capable of executing any combined operations.
Having thus far slightly considered the main principles of strategy, which space only permits us to touch on, we must for a further eluci dation of them refer our readers to the various works, such as Joininra, on this subject; and we cannot recommend a better work than the ' Elementary Treatise on Strategy,' by Edward Yates, B.A., as an intro duction to the works mentioned at the end of the article, and to general military history, by the close study of which alone can a clear know ledge of the principles of war be obtained in the cabinet, the full knowledge and power of applying which must be obtained by expe rience in time field. Yatea's • Eletnentary Treatise on Tactics' cannot be too strongly recommended as an introductory work to the study of the other branch of the science of war.
Tho manner of reconnoitring ground and performing the details of military manceuvres, has been described under Reconsstsssen, and EVOLUTIONS, MILITART. We will now proceed to a consideration of military positions and the principles of tactics with relation to the marches of armies, and the general movements on a field of battle and in a retreat.
Military positions are the sites occupied by armies either for the purpose of covering and defending certain tracts of country, or pre paratory to the commencement of offensive operations against an enemy.
A position is considered as advantageously chosen when it is on elevated ground ; when it is not commanded by eminences within the range of artillery ; and when, from the existence of natural obstacles, as rivers or marshes, on the wings, it is incapable of being turned, that is, the enemy cannot, without making an extensive movement, get to the rear of the army by which the position is occupied. In the event of such points of support being wanting, the position, whether it be a plain or an eminence, should have its flanks protected by villages, or by redoubts raised for the purpose ; for the flanks being the weakest points of the line, since the troops there are only defended by their own fire, they particularly require to be strengthened by the impedi ments of the ground, or by fortifications, in order that the enemy, in any attempt to turn the position, may be retarded till reinforcements can be brought up to oppose him.
The advantages possessed by an army on commanding ground consist in the troops being able to see the manoeuvres of the enemy while their own are concealed ; the fire, also, being directed downwards, is more effective than that of the enemy, which is made upwards from a lower level. The existence of woods or hollow ways in front of a position is considered as an unfavourable circumstance, since an enemy might there place divisions or parties for the purpose of attacking the line by surprise ; but, on the other hand, a wood in the rear, if it should not be such as to create an impediment to the passage of the troops through it, might become advantageous in the event of a retreat, as it would afford a temporary cover for the retiring columns. A village or even a single building on the ground occupied by the army may become the key of the position ; and, as frequently on the preservation of this point depends the possession of the field of battle, such point should be well supported by troops and artillery. At the battle of Coruna. in 1809, the village of Elvina was twice contested by the opposing armies ; and on the field of Waterloo, the Chateau d' Hougoumont was the object about which the action raged with the greatest violence. The highest point of ground, particularly if near the lines of operation (the roads leading to the magazines), may also constitute the key, and it is usually strengthened by one or more redoubts. It would evidently be advan tageous if such key were near the centre of the line, because, on any change in the disposition of the latter, the key might still be retained, and if the are separated from each other, it might prevent either of them from being cut off by the enemy ; whereas, if situated at one extremity, it might, on a wheel of the army taking place, become so remote as to he incapable of being supported.