can only be done by a strong hand, and this cannot be effected thoroughly without sacrifices and difficulties, nor is it the work of a moment—From this it follows that a change of the system of communication is much less easy of accomplishment in an enemy’s country than in our own, where it is at least possible; and it also follows that the army is more restricted in its movements, and must be much more sensitive about any demonstrations against its communications. But the choice and organisation of lines of communication is from the very commencement subject also to a number of conditions by which it is restricted. Not only must they be in a general sense good high roads, but they will be the more serviceable the wider they are, the more populous and wealthy towns they pass through, the more strong places there are which afford them protection. Rivers, also, as means of water communication, and bridges as points of passage, have a decisive weight in the choice. It follows from this that the situation of a line of communication, and consequently the road by which an army proceeds to commence the offensive, is only a matter of free choice up to a certain point, its situation being dependent on certain geographical relations. All the foregoing circumstances taken together determine the strength or weakness of the communication of an army with its base, and this result, compared with one similarly obtained with regard to the enemy’s communications, decides which of the two opponents is in a position to operate against the other’s lines of communication, or to cut off his retreat, that is, in technical language to _turn him_. Setting aside all considerations of moral or physical superiority, that party can only effectually accomplish this whose communications are the strongest of the two, for otherwise the enemy saves himself in the shortest mode, by a counterstroke. Now this turning can, by reason of the double signification of these lines, have also two purposes. Either the communications may be interfered with and interrupted, that the enemy may melt away by degrees from want, and thus be compelled to retreat, or the object may be directly to cut off the retreat. With regard to the first, we have to observe that a mere momentary interruption will seldom have any effect while armies are subsisted as they now are; a certain time is requisite to produce an effect in this way in order that the losses of the enemy by frequent repetition may compensate in number for the small amount he suffers in each case. One single enterprise against the enemy’s flank, which might have been a decisive stroke in those days when thousands of bread-waggons traversed the lines of communication, carrying out the systematised method then in force for subsisting troops, would hardly produce any effect now, if ever so successful; one convoy at most might be seized, which would cause the enemy some partial damage, but never compel him to retreat.