Further it is consistent with the nature of things that for the immediate wants of the present hour the _subsistence_ is the main point, but for the general efficiency of the army through a long period of time the _refitment_ and _recruitment_ are the more important, because the latter can only be done from particular sources while the former may be obtained in many ways; this again defines still more distinctly the influence of the base on the operations of the army. However great that influence may be, we must never forget that it belongs to those things which can only show a decisive effect after some considerable time, and that therefore the question always remains what may happen in that time. The value of a base of operations will seldom determine the choice of an undertaking in the first instance. Mere difficulties which may present themselves in this respect must be put side by side and compared with other means actually at our command; obstacles of this nature often vanish before the force of decisive victories. CHAPTER XVI. Lines of Communication The roads which lead from the position of an army to those points in its rear where its depôts of supply and means of recruiting and refitting its forces are principally united, and which it also in all ordinary cases chooses for its retreat, have a double signification; in the first place, they are its _lines of communication_ for the constant nourishment of the combatant force, and next they are _roads of retreat_. We have said in the preceding chapter, that, although according to the present system of subsistence, an army is chiefly fed from the district in which it is operating, it must still be looked upon as forming a whole with its base. The lines of communication belong to this whole; they form the connection between the army and its base, and are to be considered as so many great vital arteries. Supplies of every kind, convoys of munitions, detachments moving backwards and forwards, posts, orderlies, hospitals, depôts, reserves of stores, agents of administration, all these objects are constantly making use of these roads, and the total value of these services is of the utmost importance to the army. These great channels of life must therefore neither be permanently severed, nor must they be of too great length, or beset with difficulties, because there is always a loss of strength on a long road, which tends to weaken the condition of an army. By their second purpose, that is as lines of retreat, they constitute in a real sense the strategic rear of the army. For both purposes the value of these roads depends on their _length_, their _number_, their _situation_, that is their general direction, and their direction specially as regards the army, their _nature_ as roads, _difficulties_ of _ground_, the _political relations and feeling of local population_, and lastly, on the _protection_ they derive from fortresses or natural obstacles in the country.