At branches of the main boyaux they are dug a little deeper to avoid mistakes of identification. As was said before certain boyaux are organized for defense. It may be said here that supplies carried up at night are usually brought along on top of the ground close to the boyaux. This gives freer movement and the carriers are close to the cover of the trench if needed. =Accessory Defense.= Of all the accessory defenses such as barricades, abatis, trous-de-loup, etc., the most important by far is barbed wire, which is almost exclusively used for obstacles. Barbed wire should be placed from twenty to fifty yards in front of the first line. At this distance shelling of the barbed wire belts will do very little damage to the first line. The wire entanglements must be under fire of the first line. [Illustration: Command Post for Center of Resistance] The trace of the wire belt is not necessarily parallel to that of the firing line, but should be so placed as to obtain flanking fire along the wire belts. Good entanglements are constructed in double belts, the distance between the two belts being from ten to twenty yards, the farthest belt, of course, being constructed first. Breaches must be left through the wire entanglements for the passage of patrols, friendly raiding parties, etc. Portable sections of barbed wire are used to close these passages when necessary. All accessory defenses must be concealed so they cannot be easily observed and destroyed by the enemy. =Command Post.= A command post, in the full sense of the word, contains the headquarters of the leader of a division of a sector. The command post must first of all be a good observation post, after which the other requisites are installed. When the observation post has been constructed the following are built: a room for the headquarters staff to work and to sleep in, a telephone central, dugout for liaison group, and a depot. * * * * * The preceding discussion is a development of a position from battle conditions. On the other hand if you are unmolested by the enemy the order of organizing a position would be as follows: (1) Construct the emplacement to obtain flanking fire. (2) Construct barbed wire entanglements. (3) Observatory and dugouts. (4) Trenches. CHAPTER III SECTOR AND TRENCH DUTIES I. Plan of Defense =Definition.= The Plan of Defense contains all the different duties necessary to make a proper defense of the position. The execution of these duties is the execution of the Plan of Defense, which follows logically and depends directly upon the Plan of Organization.