ACCORDING to the ordinary use of language, under the term diversion is understood such an incursion into the enemy's country as draws off a portion of his force from the principal point. It is only when this is the chief end in view, and not the gain of the object which is selected as the point of attack, that it is an enterprise of a special character, otherwise it is only an ordinary attack.
Naturally the diversion must at the same time always have an object of attack, for it is only the value of this object that will induce the enemy to send troops for its protection; besides, in case the undertaking does not succeed as a diversion, this object is a compensation for the forces expended in the attempt.
These objects of attack may be fortresses, or important magazines, or rich and large towns, especially capital cities, contributions of all kinds; lastly, assistance may be afforded in this way to discontented subjects of the enemy.
It is easy to conceive that diversions may be useful, but they certainly are not so always; on the contrary, they are just as often injurious. The chief condition is that they should withdraw from the principal theatre of the war more of the enemy's troops than we employ on the diversion; for if they only succeed in drawing off just the same number, then their efficacy as diversions, properly called, ceases, and the undertaking becomes a mere subordinate attack. Even where, on account of circumstances, we have in view to attain a very great end with a very small force, as, for instance, to make an easy capture of an important fortress, and another attack is made adjoining to the principal attack, to assist the latter, that is no longer a diversion. When two states are at war, and a third falls upon one of them, such an event is very commonly called a diversion—but such an attack differs in nothing from an ordinary attack except in its direction; there is, therefore, no occasion to give it a particular name, for in theory it should be a rule only to denote by particular names such things as are in their nature distinct.
But if small forces are to attract large ones, there must obviously be some special cause, and, therefore, for the object of a diversion it is not sufficient merely to detach some troops to a point not hitherto occupied.
If the assailant with a small corps of 1000 men overruns one of his enemy's provinces, not belonging to the theatre of war, and levies contribution, etc., it is easy to see beforehand that the enemy cannot put a stop to this by detaching 1000 men, but that if he means to protect the province from invaders, he must at all events send a considerably larger force. But it may be asked cannot a defender, instead of protecting his own province, restore the balance by sending a similar detachment to plunder a province in our country? Therefore, if an advantage is to be obtained by an aggressor in this way, it must first be ascertained that there is more to be got or to be threatened in the defender's provinces than in his own. If this is the case, then no doubt a weak diversion will occupy a force on the enemy's side greater than that composing the enterprise. On the other hand, this advantage naturally diminishes as the masses increase, for 50,000 men can defend a province of moderate extent not only against equal but even against somewhat superior numbers. The advantage of large diversions is, therefore, very doubtful, and the greater they become the more decisive must be the other circumstances which favour a diversion if any good is to come out of such an enterprise upon the whole.
Now these favourable circumstances may be:—
a. Forces which the assailant holds available for a diversion without weakening the great mass of his force.
b. Points belonging to the defender which are of vital importance to him and can be threatened by a diversion.
c. Discontented subjects of the same.
d. A rich province which can supply a considerable quantity of munitions of war.
If only these diversions are undertaken, which, when tested by these different considerations, promise results, it will be found that an opportunity of making a diversion does not offer frequently.
But now comes another important point. Every diversion brings war into a district into which the war would not otherwise have penetrated: for that reason it will always be the means, more or less, of calling forth military forces which would otherwise have continued in abeyance, this will be done in a way which will be very sensibly felt if the enemy has any organised militia, and means of arming the nation at large. It is quite in the natural order of things, and amply shown by experience, that if a district is suddenly threatened by an enemy's force, and nothing has been prepared beforehand for its defence, all the most efficient official functionaries immediately lay hold of and set in motion every extraordinary means that can be imagined, in order to ward off the impending danger. Thus, new powers of resistance spring up, such as are next to a people's war, and may easily excite one.
This is a point which should be kept well in view in every diversion, in order that we may not dig our own graves.
The expeditions to North Holland in 1799, and to Walcheren in 1809, regarded as diversions, are only to be justified in so far that there was no other way of employing the English troops; but there is no doubt that the sum total of the means of resistance of the French was thereby increased, and every landing in France, would have just the same effect. To threaten the French coast certainly offers great advantages, because by that means an important body of troops becomes neutralised in watching the coast, but a landing with a large force can never be justifiable unless we can count on the assistance of a province in opposition to the Government.
The less a great decision is looked forward to in war the more will diversions be allowable, but so much the smaller will also certainly be the gain to be derived from them. They are only a means of bringing the stagnant masses into motion.
1. A diversion may include in itself a real attack, then the execution has no special character in itself except boldness and expedition.
2. It may also have as an object to appear more than it really is, being, in fact, a demonstration as well. The special means to be employed in such a case can only suggest themselves to a subtil mind well versed in men and in the existing state of circumstances. It follows from the nature of the thing that there must be a great fractioning of forces on such occasions.
3. If the forces employed are not quite inconsiderable, and the retreat is restricted to certain points, then a reserve on which the whole may rally is an essential condition.