General reliefs should not be made any oftener than necessary as they hinder methodical and continuous organization of the defense, observation of the enemy, and the preparation of contemplated offensives. It is for the express purpose of decreasing the number of general reliefs that troops are disposed in depth in a position so that continuous defense of the sector will be assured by means of successive interior reliefs. As an example of interior reliefs, we will consider a division holding a part of the front with two regiments disposed in the first position, one regiment near the second position in billets, and the fourth still farther to the rear in complete rest. These regiments, by a system of interior reliefs, will rotate to equalize the tours of duty in the first position. Similarly the battalions of the regiments in the first position will rotate to give equal divisions of time to each in the first lines. Assuming that a period of six to eight days spent in the front line is a fair average, and considering the fact that troops are disposed in depth throughout the three lines, different combinations of reliefs are possible. The work of making out the schedule of reliefs falls upon a division of the general headquarters. The sector period is variable with the activity of the enemy and conditions of life in the trenches. During the German offensive at Verdun the sector period was four days, while in Lorraine during that time the same size unit could remain in the trenches for three months without necessity of relief. II. Preliminary Dispositions for the Relief =Time to Prepare the Relief.= Usually the order for the relief is issued from the general headquarters to the regiment forty-eight hours previous to its execution. Sometimes, however, for tactical reasons, such time cannot be allowed and the regiment may have to go immediately into the trenches. In such case, the different operations of the relief, which are taken up in this chapter, are shortened but must not be carelessly executed. In the present condition of trench warfare the proper execution of a relief is of the greatest importance. =Preparation.= A relief is executed at night. Thirty-six hours before the relief is made the men of the relieving units proceed to clean and get in shape their arms, equipment, and clothing. When the relief is not for a special offensive operation, the troops go into the trenches with full equipment. All non-regulation articles are left behind with the regimental train, in care of the non-commissioned officer left with it. Also, the files, books, and official papers of the unit are left here. The regimental train establishes itself in rear of the sector of its regiment.