Lines of Communication. This term is applied to all the practicable routes and roads connecting the different parts of an army occupying the theatre of war. Therefore, as the army moves from its base, the lines of operations become lines of communication, and since these “lines of operations” are generally the longest and most important lines of communication, it is to them that the simple term “communications” generally refers. All the routes used by the trains employed in provisioning an army, form a part of the communications. The most important, safest, and most convenient of these routes, all other things being equal, will be the central one, or the one leading from the centre of the army back to its base. This particular route is sometimes designated as the “line of supplies.”—Prof. J. B. Wheeler.
Lines of Contravallation. See [Contravallation].
Lines of Operations. The roads or routes by which an army moves from its base towards its objective-point have been designated by the term “lines of operations.” Lines of operations are classified from their number into [single], [double, or multiple] lines; from their positions with respect to the lines of operations of the enemy into [interior] or [exterior] lines; and from their position with respect to each other into [convergent] or [divergent] lines. Other classifications are sometimes used descriptive of the nature or other quality of the line.
Single Line of Operations.—An army moving in a given direction with all its parts united, or with those parts so situated that they can be readily joined when required, is said to use a “single line of operations.” Sometimes this line is called a simple line. A single line of operations does not mean a single road, but embraces all the roads or routes taken by the fractions of the army for the purpose of reaching a common point of concentration; the condition being imposed that these roads shall not be so far apart, or have intervening such obstacles, that the different parts of an army will be prevented from uniting at any given time which may be appointed.
Double and Multiple Lines of Operations.—When there are obstacles intervening between the roads or routes passed over by an army, or the roads are so far apart as to prevent the parts of the army from being readily united, the army is then said to employ “double” or “multiple” lines of operations.
Interior Lines of Operations.—If these lines are within those employed by the enemy, they are known as “interior” lines.
Exterior Lines of Operations.—If these lines are outside of the lines employed by the enemy, they are called “exterior” lines.
Convergent Lines of Operations.—If these lines of operations start from points some distance apart, approach each other, and meet at some point in advance, they are called “convergent.” Sometimes the term “concentric” is employed to designate them.
Divergent Lines of Operations.—These lines are the reverse of convergent lines, as they continue to separate, or the distance between them to widen, as the army advances. The term “eccentric” is also applied to them.
Accidental Lines of Operations.—Lines of operations are sometimes employed different from those proposed in the original plan of campaign. To these lines the term “accidental” is applied. It does not follow that their adoption is a matter of accident, as might be inferred from their name. They are frequently the result of a change in the original plan, which probable change was foreseen and provided for.