Again, any point which covers the line of retreat of a defensive army, which is strong enough to be maintained by that army, and which from its position cannot be turned or passed by an enemy with impunity, is a decisive strategical point — for defence.

From this definition it will be seen that any point on the theatre of war may become a decisive strategical point. Its doing so must depend on the relative situations of the hostile armies.

But those which are most likely to become so are as below enumerated, in the order of their import

ance.

Class 1. Fortified places or strong positions commanding the principal great roads which traverse the theatre of war. The greater the number of roads which centre in such places the greater the importance of those places as strategical points.

Class 2. Fortified places commanding a permanent bridge over a great river. A fortress which defends the approach to a bridge on both sides is evidently of more importance as a strategical point than one which commands one side only. And a fortress situated at the confluence of two great rivers and commanding a passage over both, is evidently more important still.

Class 3. Fortified places blocking up the approach to passes over a range of mountains. These are

analogous to Class 2. And fortresses which block

up the valleys where two ranges cross or meet one another are analogous to those which are described in Class 2 as situated at the confluence of two great rivers.

It is possible for a strategical point to combine the conditions of all the above three classes; it will then become, if employed, a decisive strategical point of the very highest order. Ulm may be cited as an example of such a point. It satisfies the conditions of Class 1 by being at the junction of five principal roads; those of Class 2 by being situated at the confluence of the Danube and Iller; those of Class 3 by blocking up the valleys of both those rivers, being situated at the point where their valleys cross one another.

Fortified harbours may be considered as a 4th class where the command of the sea accompanies their

session.

pos

F

CHAP. II.

BASES AND COMMUNICATIONS.

"Le secret de la guerre est dans le secret des communications."-Napoleon.

THE first consideration in commencing a campaign either offensive or defensive, is the base of operations.

The base of an offensive army is generally a part of the line of frontier which separates it from the theatre of war.

The base of a defensive army whose territory is invaded is, generally speaking, the capital of the country. If this should fall into the power of the invaders, in all probability the war would terminate ; but if still able to continue the contest, the defensive force can choose any convenient point, line, or district in the country, not actually occupied by the invading army, as its base. It will naturally be that from which the greatest amount of injury can be inflicted on the enemy; and this object will be best accomplished by operating on his communications in accordance with Principle 2.

The choice of a base depends on the considerations which have determined the plan of a campaign.

But here the question will be considered purely in a military view, without reference to political or moral influences.

Any part of a frontier may be chosen as the base from which an army marches to invade an enemy's territory, provided it satisfy the conditions given in the definition.

Its configuration may be straight, curved, or angular.

Of these the least advantageous is a straight base. In this case the line of march of the army is necessarily perpendicular to its base, and the strategical front of the army is parallel to it.

If it should happen that the enemy's base is of the same description and parallel to that of the army, there is no advantage on either side in this particular.

For let

A and B be two armies, which have respectively advanced from parallel bases a b, c d; it is clear that A cannot place itself in a position A', so as to apply Principle 2; for, although that position would

threaten B's communications, those of A would be equally exposed to attack from B.

Curved or angular bases have different degrees of advantage according to circumstances; but they are all more advantageous than a straight base, as they all more or less afford an opportunity of applying Principle 2.

A curved base may be either convex towards the enemy or concave. The accompanying diagrams will explain the peculiar advantages of each.

a b (No. 1) is the concave base of a.

The flanks being advanced, an army operating from either flank can place itself more or less on the flank and rear of a hostile army B advancing towards a b, evidently more the nearer B approaches. This is an advantage. The disadvantage is that when A shall have fallen back before B, and retired