The guarding of camps is a very important matter, and requires much attention.

The camp-guard consists of one or two rows of sentinels placed around the camp, and relieved at regular intervals.  The number of rows of sentinels, and the distance between each man, will depend upon the character of the ground and the degree of danger apprehended.

Detachments of infantry and cavalry, denominated picquets, are also thrown out in front and on the flanks, which, in connection with the camp-guards, serve to keep good order and discipline in and around the camp, to prevent desertions, intercept reconnoitering parties, and to give timely notice of the enemy’s approach.

Still larger detachments, denominated grand-guards, are posted in the surrounding villages, farm-houses, or small field-works, which they occupy as outposts, and from which they can watch the movements of the enemy, and prevent any attempts to surprise the camp.  They detach patrols, videttes, and sentries, to furnish timely notice of danger.  They should never be so far from the camp as to be beyond succor in case of sudden attack.  Outposts, when too far advanced, are sometimes destroyed without being able to give notice of the enemy’s approach.

In encamping troops in winter-quarters, it is sometimes necessary to scatter them over a considerable extent of ground, in order to facilitate their subsistence.  In such a case, the arrangement of guards requires the utmost care.  A chain of advanced posts should be placed several miles’ distance from the line of camp; these posts should be supported by other and larger detachments in their rear, and concentrated on fewer points; and the whole country around should be continually reconnoitered by patrols of cavalry.

The manner in which Napoleon quartered and wintered his army on the Passarge, in 1806-7, furnishes a useful lesson to military men, both in the matters of encampment and subsistence.  An immense army of men were here quartered and subsisted, in a most rigorous climate, with a not over fertile soil, in the midst of hostile nations, and in the very face of a most powerful enemy.

A Roman army invariably encamped in the same order, its troops being always drawn up in the same battle array.  A Roman staff-officer who marked out an encampment, performed nothing more than a mechanical operation; he had no occasion for much genius or experience.  The form of the camps was a square.  In later times, they sometimes, in imitation of the Greeks, made them circular, or adapted them to the ground.  The camp was always surrounded with a ditch and rampart, and divided into two parts by a broad street, and into subdivisions by cross-streets and alleys.  Each tent was calculated to hold ten privates and a petty officer.

In the middle ages, the form of the camp did not differ very essentially from that of the Romans, the variation consisting principally in the interior arrangements, these arrangements being made to correspond to the existing mode of forming a line of battle.  The details of this system may be found in the military work of Machiavelli.