army has run its career, and therefore can neither make use of a fresh victory over our army, nor can he pursue us if we evade a combat by moving out of the way.
This last case, which is by no means so uncommon as might be supposed, we shall lay aside for the moment, and occupy ourselves with the accessory conditions of the first.
The first of these is, that the communications have a certain length, and cannot be protected by a few good posts; the second point is, that the situation of the line is such as exposes it to our action.
This weakness of the line may arise in two ways—either by its direction, if it is not perpendicular to the strategic front of the enemy’s army, or because his lines of communication pass through our territory; if both these circumstances exist, the line is so much the more exposed. These two relations require a closer examination.