Smoke will be used by every fighting arm of the Service in practically every battle, both by day and by night. If you have ever tried on a target range to shoot at a target that was just beginning to be obscured by a fog, you will recognize the difficulty of hitting anything by firing through an impenetrable smoke screen. It is simply a shot in the dark. Future battles will witness smoke formed by smoke candles that are kept in the trenches or carried by the troops, by smoke from bursting artillery shell and rifle grenades, by smoke from aeroplane bombs and possibly even from what is known as the smoke knapsack. The knapsack produces a very dense white smoke and very economically, but will probably not be much used. This is because, notwithstanding its efficiency, the knapsack cannot be projected to a distance, that is, the smoke screen is generated on the person carrying the knapsack. On the other hand the great value of phosphorus is that it can be fired to great distances in rifle grenades or artillery shell, and dropped from aviation bombs. The smoke screen is thus established in front of the object it is desired to cut off, whether it be a battery of artillery, an advancing wave of infantry, or a lookout station. Thus smoke, for screening purposes alone, will be used to a tremendous extent. It will also be used in conjunction with gas. SMOKY APPEARANCE OF GAS CLOUD Due to the smoky appearance of an ordinary gas cloud and to the coming use of poisonous smokes, no one on the field of battle in the future will ever be certain that any given smoke cloud is not also a poisonous cloud until he has actually tested it. And there lies an opportunity for the most intense study and for the greatest use of the proverbial American ingenuity that war has ever furnished. In the variations that can be played with smoke containing gas, or not containing gas, with smoke hurled long distances by the artillery or dropped from aeroplanes, the possibilities indeed are unlimited. Every officer will need to study the possibilities of smoke, both in its use against him and in his use of it against the enemy. He can probably save more casualties among his own troops by the skillful use of smoke than by any other one thing at his command. On the other hand, the unskilled use of smoke on the part of one side in a battle may lead to very great casualties in proportion to those of the enemy should the latter use his smoke skillfully. This is a subject that deserves deep and constant study. PROTECTION BY SMOKE CLOUDS Smoke in the future will be the greatest protective device available to the soldier. It shuts out not only the view in daylight, but the searching of ground at night by searchlights, by star bombs or other means for illuminating the battlefield. It has already been used extensively by the Navy and undoubtedly will be used far more extensively in the future. SHELL MARKINGS