Therefore supposing the distance to be a march of four miles, for which usually ten hours are required, then from the moment that the enemy appears in force in front of the advanced corps, we may reckon upon fifteen hours before he is in a condition to attack our main body. On the other hand, if the advanced guard is posted only a mile in advance, then the time which will elapse before our army can be attacked will be more than three or four hours, and may very easily come up to double that, for the enemy still requires just as much time to mature his first measures against our advanced guard, and the resistance offered by that guard in its original position will be greater than it would be in a position further forward. The consequence is, that in the first of these supposed cases the enemy cannot easily make an attack on our main body on the same day that he presses back the advanced corps, and this exactly coincides with the results of experience. Even in the second case the enemy must succeed in driving our advanced guard from its ground in the first half of the day to have the requisite time for a general action. As the night comes to our help in the first of these supposed cases, we see how much time may be gained by an advanced guard thrown further forward. With reference to corps placed on the sides or flanks, the object of which we have before explained, the mode of action is in most cases more or less connected with circumstances which belong to the province of immediate application. The simplest way is to look upon them as advanced guards placed on the sides, which being at the same time thrown out somewhat in advance, retreat in an oblique direction upon the army. As these corps are not immediately in the front of the army, and cannot be so easily supported as a regular advanced guard, they would, therefore, be exposed to greater danger if it was not that the enemy’s offensive power in most cases is somewhat less at the outer extremities of his line, and in the worst cases such corps have sufficient room to give way without exposing the army so directly to danger as a flying advanced guard would in its rapid retreat. The most usual and best means of supporting an advanced corps is by a considerable body of cavalry, for which reason, when necessary from the distance at which the corps is advanced, the reserve cavalry is posted between the main body and the advanced corps. The conclusion to be drawn from the preceding reflections is, that an advanced corps effects more by its presence than by its efforts, less by the combats in which it engages than by the possibility of those in which it might engage: that it should never attempt to stop the enemy’s movements, but only serve like a pendulum to moderate and regulate them, so that they may be made matter of calculation. CHAPTER IX. Camps