The smaller a body of troops the more easily it can be moved, and therefore the less it requires that subdivision which is not a result of the separate disposition, but of the unwieldiness of the mass. A small body, therefore, can march upon one road, and if it is to advance on several lines it easily finds roads near each other which are as good as it requires. The greater the mass the greater becomes the necessity for subdividing, the greater becomes the number of columns, and the want of made roads, or even great high roads, consequently also the distance of the columns from each other. Now the danger of this subdivision is arithmetically expressed in an inverse ratio to the necessity for it. The smaller the parts are, the more readily must they be able to render assistance to each other; the larger they are, the longer they can be left to depend on themselves. If we only call to mind what has been said in the preceding book on this subject, and also consider that in cultivated countries at a few miles distance from the main road there are always other tolerably good roads running in a parallel direction, it is easy to see that, in regulating a march, there are no great difficulties which make rapidity and precision in the advance incompatible with the proper concentration of force. In a mountainous country parallel roads are both scarce, and the difficulties of communication between them great; but the defensive powers of a single column are very much greater. In order to make this idea clearer let us look at it for a moment in a concrete form. A division of 8,000 men, with its artillery and other carriages, takes up, as we know by experience in ordinary cases, a space of one league; if, therefore, two divisions march one after the other on the same road, the second arrives one hour after the first; but now, as said in the sixth chapter of the fourth book, a division of this strength is quite capable of maintaining a combat for several hours, even against a superior force, and, therefore, supposing the worst, that is, supposing the first had to commence a fight instantaneously, still the second division would not arrive too late. Further, within a league right and left of the road on which we march, in the cultivated countries of central Europe there are, generally, lateral roads which can be used for a march, so that there is no necessity to go across country, as was so often done in the Seven Years’ War.