If an army sets out on any expedition, whether it be to attack the enemy and his theatre of war, or to take post on its own frontier, it continues in a state of necessary dependence on the sources from which it draws its subsistence and reinforcements, and must maintain its communication with them, as they are the conditions of its existence and preservation. This dependence increases in intensity and extent in proportion to the size of the army. But now it is neither always possible nor requisite that the army should continue in direct communication with the whole of its own country; it is sufficient if it does so with that portion immediately in its rear, and which is consequently covered by its position. In this portion of the country then, as far as necessary, special depôts of provisions are formed, and arrangements are made for regularly forwarding reinforcements and supplies. This strip of territory is therefore the foundation of the army and of all its undertakings, and the two must be regarded as forming in connection only one whole. If the supplies for their greater security are lodged in fortified places, the idea of a base becomes more distinct; but the idea does not originate in any arrangement of that kind, and in a number of cases no such arrangement is made. But a portion of the enemy’s territory may also become a base for our army, or, at least, form part of it; for when an army penetrates into an enemy’s land, a number of its wants are supplied from that part of the country which is taken possession of; but it is then a necessary condition that we are completely masters of this portion of territory, that is, certain of our orders being obeyed within its limits. This certainty, however, seldom extends beyond the reach of our ability to keep the inhabitants in awe by small garrisons, and detachments moving about from place to place, and that is not very far in general. The consequence is, that in the enemy’s country, the part of territory from which we can draw supplies is seldom of sufficient extent to furnish all the supplies we require, and we must therefore still depend on our own land for much, and this brings us back again to the importance of that part of our territory immediately in rear of our army as an indispensable portion of our base.