of parts is a thing as obvious as it is positive, and this idea furnishes real strategic motives for determining the number of the greater divisions of an army, consequently their strength, whilst the strength of the smaller divisions, such as companies, battalions, etc., is left to be determined by tactics.
We can hardly imagine the smallest independent body in which there are not at least three parts to be distinguished, that one part may be thrown out in advance, and another part be left in rear: that four is still more convenient follows of itself, if we keep in view that the middle part, being the principal division, ought to be stronger than either of the others; in this way, we may proceed to make out eight, which appears to us to be the most suitable number for an army if we take one part for an advanced guard as a constant necessity, three for the main body, that is a right wing, centre and left wing, two divisions for reserve, and one to detach to the right, one to the left. Without pedantically ascribing a great importance to these numbers and figures, we certainly believe that they represent the most usual and