Under these circumstances the march off from the right or left is of no consequence now, otherwise than that when it is done alternately it tends to equalise the fatigue which the troops undergo. This, which is the only object, is certainly an important one for retaining both modes of marching off with large bodies. The advance from the centre as a definite evolution naturally comes to an end on account of what has just been stated, and can only take place accidentally. An advance from the centre by one and the same column in strategy is, in point of fact, nonsense, for it supposes a double road. The order of march belongs, moreover, more to the province of tactics than to that of strategy, for it is the division of a whole into parts, which, after the march, are once more to resume the state of a whole. As, however, in modern warfare the formal connection of the parts is not required to be constantly kept up during a march, but on the contrary, the parts during the march may become further separated, and therefore be left more to their own resources, therefore it is much easier now for independent combats to happen in which the parts have to sustain themselves, and which, therefore must be reckoned as complete combats in themselves, and on that account we have thought it necessary to say so much on the subject. Further, an order of battle in three parts in juxtaposition being, as we have seen in the second 1 chapter of this book, the most natural where no special object predominates, from that results also that the order of march in three columns is the most natural. It only remains to observe that the notion of a column in strategy does not found itself mainly on the line of march of one body of troops. The term is used in strategy to designate masses of troops marching on the same road on different days as well. For the division into columns is made chiefly to shorten and facilitate the march, as a small number marches quicker and more conveniently than large bodies. But this end may, be attained by marching troops on different days, as well as by marching them on different roads. CHAPTER XI. Marches (_Continued_) Respecting the length of a march and the time it requires, it is natural for us to depend on the general results of experience. For our modern armies it has long been settled that a march of three miles should be the usual day’s work which, on long distances, may be set down as an average distance of two miles per day, allowing for the necessary rest days, to make such repairs of all kinds as may be required. Such a march in a level country, and on tolerable roads will occupy a division of 8,000 men from eight to ten hours; in a hilly country from ten to twelve hours. If several divisions are united in one column, the march will occupy a couple of hours longer, without taking into account the intervals which must elapse between the departure of the first and succeeding divisions.