Have they any idea of our own activities? What is the nature and the location of their accessory defences? What is the location of their machine guns, trench mortars? Have they any asphyxiating gas or liquid fire apparatus? Have they abundant supplies of hand grenades, etc., etc. DEVICES TO DRAW THE ENEMY'S FIRE. 42.--To make enemy waste ammunition. Any devices which lead the enemy to waste ammunition or to expose themselves is a clear gain. Many may be readily devised and officers and men should be encouraged to do so. The following have often proved successful: 43.--Pretend abandoning trench. Remain absolutely quiescent during several days. This may lead the enemy to send out patrols or raiding parties which may be the more surely destroyed. They should be allowed to approach to the wire entanglements before a shot is fired. 44.--Pretend a raid. On dark nights, have all firing stop. Throw stones by hand or with slings, a dozen at a time toward the enemy's trench. This will lead him to fire repeated volleys and waste ammunition in his fear of an attack, especially if the trenches are in wooded terrain and there are leaves on the ground. Repeat several times during the night. Patrols may also tie strings to the enemy's barb wire. On dark nights pulling on the string may lead the enemy to fire. 45.--Use decoys. Decoys may be arranged in trees or stuck up momentarily over the parapet. They will draw the enemy's fire. 46.--Pretend a fire attack. If the enemy's trenches are near enough for the sound to carry, whistles may be blown all along the line before a volley. They may be blown again after the command to omit the volley. The enemy may continue to fire indefinitely. 47.--Watch out for enemy's ruses. Let the aim of all these devices be to make the enemy waste ammunition and to save your own. On the other hand, the enemy is likely to attempt like ruses and many others which are not permissible such as the use of white flags or raising hands to indicate pretended surrender. 48.--His use of blank cartridges. A legitimate ruse, of which the enemy is fond and which should be guarded against, consists in their firing blank cartridges to mask an advance of their men. It is clear that men do not advance while bullets are fired from their own trenches. Nor does one fire in retaliation until the enemy's fire ceases. A little attention will be sufficient to spoil this plan as, when only blank cartridges are fired, no bullets will whiz by. As long as the enemy fires blank cartridges, withhold your own fire, be on guard against the appearance of patrols and be ready to receive them when they draw near. 49.--His use of flares. In case the enemy sends up flares, patrols should lie flat and motionless till after the volley which often follows. The sentinels in the fire trench should note spot where flare was sent up and abstain from firing unless enemy is sighted out of his trenches. 50.--His machine guns.