It will therefore be necessary for the units to practise intrenchment on a large scale, and finally to perfect their instruction by exercise over shell-torn ground similar to that of the Front. We would suggest, in order to familiarize the troops with the actual mode of destroying defensive works, practice with such obsolete artillery as is not fitted for use at the Front. It is of paramount importance also to accustom the men as rapidly as possible to the sight and sound of gun-fire. We would suggest that the final exercises of assault be accompanied by curtain fires made, to avoid all risks of accident, at about three hundred metres in advance of the first lines. We can add that the mode of instruction we advocate here would be as beneficial to the Chiefs as to the men. Thus only will they fully realize beforehand the difficulties they will meet when facing the one factor which it is impossible to include in any course of training--the Enemy; an enemy that, to the end, will be skilled and formidable. INDEX Aërial torpedoes, 84 _Agents de liaison_, 19 Air supremacy, 46 Ammunition (different issues), 109 Anti-aircraft artillery, 92 Armoured motor-cars, 94 Army, 17 Army corps, 17 Army group, 17 Artillery, 19, 68, 77, 80 Artillery (advance), 95 Artillery of an army corps, 81 Artillery in trenches, 68 Artillery of a division, 82 Asphyxiating gas, 17, 89, 150, 152 Asphyxiating projectiles, 37 Assaulting and occupation troops, 135 Attack in Artois, 13 Automatic pistols, 121 Aviation, 29, 45 Aviators (British), 46 Balloons, 28, 43 Barrage, 44, 87, 92, 109, 138, 143 Bastion, 59 Battalions of three companies, 147 Battle planes, 20, 34, 36 Bayonet, 118 Biplanes, 34 Blockhouses, 64 Boardwalk flooring, 61 Bombardments, 40 Bombing planes, 36 _Boyaux_, 64, 66, 67 Brigade, 19 Burros, 105 Camouflage, 63, 75, 106 Camouflet, 70 Carrel, Dr. Alexis, 22 Carrier pigeons, 145 Casemates, 68 Cavalry, 19, 148 Centres of resistance, 55, 64 Check positions, 65 Citations, 127 _Clayonnages_, 60 Command, 22 Commissariat department, 20 Communication tunnels, 57, 64, 66, 67 Compressed air mortars, 84 Counterfiring, 88 Craters, 53, 70 Defensive, 134 Defensive engagements, 142 Destructive fire, 88 Dirigible balloons, 49 Division, 17, 131 Division front, 131 Division (General), 22 Division, its dispositions, 132 Dugouts, 57, 64 Engineers, 19 Engineers (American), 74 Field artillery, 86, 92, 143 Field batteries, 81 Firing tables, 87 “Flaming onions,” 94 Framework of the army, 147 Fronts (distance between), 52 _Gaz-vésicant_, 152 Grenades, 53, 117, 119 Gun (37 mm.), 94 Guns (75 mm., 87 mm.), 87 Guns (120, 155, 220, 270, 280, 305, 370, 400, 520, 19, 100, 240, 224, 305, 340 mm.), 80 Guynemer (Captain), 34 Harvest, 39