Apart from a number of fairly big bombardments, like that at Arras, mentioned above, the destructive shoots were chiefly counter-battery ones, intended if possible to “neutralise” our artillery while it should be actively engaged in putting down a barrage, either to prevent a German attack or in preparing the way for our own infantry when we were attacking, which, of course, was much more frequently the case in 1916 and the first half of 1917. This neutralisation business wants a bit of explaining. It will have been realised that the Germans were and still are using two very distinct kinds of gas shell--those which kill, like the Green Cross, and those which only temporarily put a man out of action, like the lachrymators and nowadays the mustard gas. Of course, the idea underlying the use of gas shell in general--and the whole war for that matter--is to put men out of action. The most effective way of doing this is to kill, as that puts a man out of action for good and he doesn’t return. But you can kill men with gas only by taking them by surprise, because of the excellence of the gas masks. After the surprise has been effected the chief use of the gas shell is to force the opposing side to continue wearing their gas masks and in that way to hamper them and reduce their fighting efficiency for considerable lengths of time. This is where the lachrymators and mustard gas and similar stuffs come in, because they are very persistent, and a little goes a long way in forcing a man to keep his respirator on. The quick-killing gases, like phosgene and the Green Cross, are not very persistent, and it would be waste of material to continue shooting them when you could effect the same thing with another stuff, which would hang about for hours or perhaps for days. Now see how this affected the German “fire for effect,” or destructive shooting, as applied to a battery, and why the gas shell are so particularly suited for taking on targets of this kind, which used to be engaged only by high-explosive shell. Imagine a battery of, let us say, field howitzers. Our men are making an attack. The howitzers are busy pounding the German trenches to bits, and then they are going to “lift” on to the support trenches when our men go in. The whole of the success of the infantry assault may rest on the guns’ keeping up to the program with the requisite amount of fire. The boche business then is to try to put our guns out of action. If he can do this he has the infantry--I won’t say at his mercy, but at any rate at such a serious disadvantage that their losses will be tremendous compared with what they would be under cover of a good barrage from the guns.