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. In the foregoing observations we have lost sight altogether of _outposts_, and therefore we must now return to them again. In saying, at the commencement, that the relations between outposts and stationary troops is similar to that between advanced guards and troops in motion, our object was to refer the conceptions back to their origin, and keep them distinct in future; but it is clear that if we confine ourselves strictly to the words we should get little more than a pedantic distinction. If an army on the march halts at night to resume the march next morning, the advanced guard must naturally do the same, and always organise the outpost duty, required both for its own security and that of the main body, without on that account being changed from an advanced guard into a line of outposts. To satisfy the notion of that transformation, the advanced guard would have to be completely broken up into a chain of small posts, having either only a very small force, or none at all in a form approaching to a mass. In other words, the idea of a line of outposts must predominate over that of a concentrated corps.