In time there is a complete skeleton of a series of lines of trenches outlining a position. If the mission of the troops is to remain and hold the ground, the necessary plan of organization for the final position will have to be based upon this skeleton. The purpose of this new organization, as we have noted, is to establish the position so that the ground can be held by fewer troops. =Active and Passive Elements of a Position, Especially Support Points.= The first fire trench of a position is continuous, but it is not good practice to man the whole of this line, because this would take too many men and defeat the purpose of the fortifications. Secondly, a better defense can be established by garrisoning a series of strong points, or salients, from which can be obtained flanking fire. In the first line these are called support points. The trenches connecting these support points are retained as such, but are not usually manned. This curtain trench, so to speak, is retained for communicating purposes, and to deceive the enemy as to the real points of defense. A few watchers are left in it. The first line, then, is a series of support points, well defended by men and special weapons, and at such distances apart as to support each other. =Division of Position.= The garrison of such a support point in the first line is a company, and the captain is responsible for the holding of this ground. (The platoon, we must remember, is a tactical unit.) In dividing the first line into these active elements the size of each support point depends upon the importance of the ground or of the tactical situation. [Illustration] Similar natural strong points are also located in the second line. They will be fewer and farther apart in this line than in the first line, which is exposed to hostile attacks. These points in the second line are connected with the support points and together the group is called a center of resistance. The command of such a center of resistance, including one or two support points in the front line, falls to a battalion commander with his unit. For example, the area of a center of resistance under the command of a Bn. C. O. will include, say, two support points in the first line with a company in each, and the strong point in the second line with two companies. In the third line, also, natural strong points are located and organized for defense. The command of this strong point, including, let us say, two centers of resistance, falls to a colonel with his regiment. Such an area is called a sector, or a sub-sector. If it is a sub-sector two such constitute a sector in command of a brigadier-general. =Different Lines of a Sector.= We have now arrived automatically at the fact that each sector is composed of a series of lines in depth, each defended in strong points. The first line is termed the line of resistance, as the first defense is made against the enemy’s attacks in the support points of this line. [Illustration]