During the raid, the support artillery establishes protective curtains of fire on both flanks and on the rear of the raided portion of the enemy’s line. This is to neutralize the enemy’s defenses and to cut the area off from communications or reinforcements. In other words, the artillery will isolate by its fire the point of attack of the raid. At the designated time for the return of the raid or at the signal of a rocket sent up by the raiding party on reaching their own first line, the support artillery establishes its usual defensive barrage in “No Man’s Land.” It may also fire on the enemy’s position with shrapnel, because at this time reinforcements are usually coming up into the raided area. This latter fire may be repeated two or three times during the ensuing hour. II. Gas Warfare Gas attacks may be carried out in two ways, by asphyxiating shells or by waves of gas. The shelling of a position with asphyxiating shells is made to neutralize the action of its defenders and, if possible, to kill and wound some of them. Asphyxiating shells are used in counter-battery fire against the enemy’s artillery emplacements. They are also used for shelling a woods in which troops are located and against strong points of the hostile position, either during an offensive period or to carry out attrition of the enemy. Such shelling is also carried out for an offensive, either in the preparation or for the protection of the flanks during the attack. Asphyxiating shells may be thrown on a village or strong point in rear or on the flank of the enemy’s position where he may organize a counterattack. Gas waves are used against the enemy’s position with or without following up with the infantry for a raid or an attack. Usually the liquified gas is brought to the first lines in cylinders under heavy pressure. These cylinders must be properly protected from hostile fire until the time that they are to be used. With a favorable wind, the gas is carried across “No Man’s Land” and into the enemy’s position. Gas waves, of course, are more efficient than asphyxiating shells, but the use of the former method is more difficult as it takes special apparatus and a trained personnel, and can be used only under favorable atmospheric conditions. =Protections against Gas.= In general, protective measures against gas waves are the same as against asphyxiating shells. The individual protective apparatus is the gas mask. The essential part of a mask is composed of several layers of porous material containing a chemical that will neutralize the poisonous gas. The gas mask has an efficiency of several hours. Each man carries a gas mask and there are also a certain number kept in reserve in the different depots of the sector. Each gas mask must be properly adjusted and it is the duty of each officer and non-commissioned officer to ascertain that each man in the company has a gas mask in good condition. He must always carry the same.