Again, it is known by experience that the head of a column composed of four divisions and a reserve of cavalry, even on indifferent roads, generally gets over a march of three miles in eight hours; now, if we reckon for each division one league in depth, and the same for the reserve cavalry and artillery, then the whole march will last thirteen hours. This is no great length of time, and yet in this case forty thousand men would have marched over the same road. But with such a mass as this we can make use of lateral roads, which are to be found at a greater distance, and therefore easily shorten the march. If the mass of troops marching on the same road is still greater than above supposed, then it is a case in which the arrival of the whole on the same day is no longer indispensable, for such masses never give battle now the moment they meet, usually not until the next day. We have introduced these concrete cases, not as exhausting considerations of this kind, but to make ourselves more intelligible, and by means of this glance at the results of experience to show that in the present mode of conducting war the organisation of marches no longer offers such great difficulties; that the most rapid marches, executed with the greatest precision, no longer require either that peculiar skill or that exact knowledge of the country which was needed for Frederick’s rapid and exact marches in the Seven Years’ War. Through the existing organisation of armies, they rather go on now almost of themselves, at least without any great preparatory plans. In times past, battles were conducted by mere word of command, but marches required a regular plan, now the order of battle requires the latter, and for a march the word of command almost suffices. As is well known, all marches are either perpendicular [to the front] or parallel. The latter, also called flank marches, alter the geometrical position of the divisions; those parts which, in position, were in line, will follow one another, and _vice versa_. Now, although the line of march may be at any angle with the front, still the order of the march must decidedly be of one or other of these classes.