The machine gun is the best weapon for flanking fire. Several emplacements are constructed for each machine gun, but during the bombardment it is kept under cover in a dugout. When the attack develops the machine gun is quickly set up in the proper emplacement. If kept in a permanent emplacement the enemy will soon locate it and put it out of business by artillery fire. If no emplacements are possible or if they are destroyed machine guns are operated on open ground or in shell holes. =Field of Fire.= With proper flanking fire a line can be defended with a shorter field of fire than otherwise. A hundred yards of field of fire is sufficient with good flanking fire and accessory defenses, such as barbed wire, etc. [Illustration: DIVISION OF POSITION INTO COMPARTMENTS FOR INTERIOR DEFENSE] =Location of Trenches.= Lines of trenches which are the result of a battle are not always located in the most logical positions. They are the results of the exigencies of the battle. However, it is well to know the best locations for the trenches of a position under different conditions in order to place them there when possible. In flat country, of course, it makes no difference where the trenches are located. On the profile of a hill, however, the question is where to locate the first and where to locate the second line. Let us consider Figure 15. Point A is out of the question as you have no view of the enemy. At B you can observe the enemy’s line and he can observe yours. However, the enemy can shell you at this point and observe the results. At C the same conditions obtain as at B, except there is a dead angle directly in front. At D you cannot observe the enemy nor can the enemy observe your line. From these considerations we see that the proper location for the first line will be at B as you must be able to observe the enemy and all the ground in front. Your second line should be located at D where the enemy cannot observe and bombard your position. At D the line can be made as elaborate as you have time, men, and material, because you are more or less unmolested by the enemy’s fire and observation. The reverse slope is of the very greatest importance in organizing a position. Movements of troops and supplies can be easily accomplished here under cover. Deep dugouts can be constructed with the least work. But the greatest advantage lies during the bombardment. The enemy is not able to observe the accuracy of his fire on the reverse slope so that the elements in this line are left more or less intact. For this reason the line on the reverse slope becomes the most important line of resistance against the enemy’s attacks. The Germans habitually organize their reverse slopes very strongly.