[Illustration: PLATE 45a.—Trench showing wire overhead cover and wire trapdoor obstacle. Machicoulis gallery in background.] Any observations of enemy activities, of any nature whatever, are reported immediately so that they may be passed on to the commander whose unit is manning the trenches directly opposite the same. Loopholes should be screened at the rear by a sandbag split and hung over them. They should be carefully concealed to prevent their location being discovered by the enemy. There must be no alteration in the parapet where they are located. [Sidenote: Snipers] The enemy’s sojourn in the trenches should be made as disagreeable to him as possible. He must be kept continually on the alert. Our operations must be made a constant menace to him. It is in this way that casualties are effected and he is gradually worn out. One of the best methods of accomplishing all of the above is the employment of snipers, who are specially selected and trained in this branch of trench warfare. The snipers are on duty all day, but they have their nights in bed. They conduct their operations in pairs and are given a definite post to occupy and in exceptional cases may be given a roving commission. The advantage of having the same men regularly on the same post is that they learn thoroughly the appearance of every square foot of the ground included in their area of observation and are able immediately to note any change that may take place. They soon learn where to look for the enemy and in fact learn the habits, etc., of the enemy occupying their sphere of observation. The sniper must be an expert in: 1. The construction of loopholes by day and by night. 2. The use of telescopic sights, field glasses, periscopes and all optical contrivances designed for observation purposes. 3. The selection of good positions for sniping. 4. Judging distances and estimating or measuring ranges. 5. Rifle firing. He should be an expert rifleman in order that full advantage may be taken of the opportunities to inflict losses on the enemy. 6. In trench warfare each pair of snipers will be required to report each evening to the company commander the result of their day’s operations. [Sidenote: What to Fire At] When the enemy makes his attack you will generally fire at those who appear in the sector that has been allotted to you to cover. You may, however, abandon your target on your own initiative under the following circumstances and fire: 1. On officers and noncommissioned officers. These can be recognized by their gestures. They are generally in the center of groups and get up and start first. They should be disabled, as this is the surest way of breaking up the attack.