But this disposition in three columns of equal strength is one which is by no means to be recommended, partly on that account, and also because the division of a whole army into three parts makes it very unmanageable, as stated in the fifth chapter of the third book.
When the whole is formed into a centre with two wings separate from it, which we have represented in the preceding chapter as the most natural formation as long as there is no particular object for any other, the corps forming the advanced guard, according to the simplest notion of the case, will have its place in front of the centre, and therefore before the line which forms the front of the wings; but as the first object of corps thrown out on the flanks is to perform the same office for the sides as the advanced guard for the front, it will very often happen that these corps will be in line with the advanced guard, or even still further thrown forward, according to circumstances.
With respect to the strength of an advanced guard we have little to say, as now very properly it is the general custom to detail for that duty one or more component parts of the army of the first class, reinforced by part of the cavalry: so that it consists of a corps, if the army is formed in corps; of a division, if the organisation is in divisions.
It is easy to perceive that in this respect also the great number of higher members or divisions is an advantage.
How far the advanced guard should be pushed to the front must entirely depend on circumstances; there are cases in which it may be more than a day’s march in advance, and others in which it should be immediately before the front of the army. If we find that in most cases between one and three miles is the distance chosen, that shows certainly that circumstances have usually pointed out this distance as the best; but we cannot make of it a rule by which we are to be always guided.