The artillery may determine the exact range to some zone which the advancing infantry has to cross and, as the infantry reaches it, open a heavy and accurate fire. The infantry must cross this zone in a formation which decreases its vulnerability as much as practicable, consistent with other conditions, such as the hostile infantry fire. The enemy’s guns can get you if they expend enough ammunition at the task; but can they afford the ammunition? Your own artillery may interfere with such an expenditure even if the enemy were willing to make it. A division deployed with 2500 men on the firing line, crossing correctly in thin lines a fire-swept zone from 4000 to 1200 yards, might lose 10% of this number from artillery fire and not have its advance even checked. With this open formation the loss is so small that the moral effect of it will be negligible with trained men. But a loss of 250 men at an expenditure of 160 shrapnel for each means 40,000 shrapnel. Even half that much would be more than could generally be afforded. [Sidenote: Forming skirmish line] After the skirmish line is formed at the position for opening the infantry attack, the further advance from there is conducted as already explained. In skirmish line the hostile infantry is now by far your most dangerous foe, but the artillery will still be punishing you: your line must advance under both fires. Artillery fire will seldom be uniformly distributed along the entire skirmish line or continuous in its action. There will be blasts of intense fire, then a lull. The troops must be trained to take advantage of these lulls to advance and to lie quiet during the periods of hottest fire. Of course, if for any cause the artillery fire is not very effective, the advance continues as against the infantry. Our infantry must be taught to keep their fire superiority over the hostile infantry and to this object to devote all their skill and energy, but to avoid unnecessary heavy loss from artillery whenever possible. The hostile infantry is their real opponent, their real danger. As the opposing lines get close the losses from artillery fire become relatively slight, compared with the losses from infantry fire. [Sidenote: How to practice advance under artillery fire] How are we to get this training in most of our posts where there is no artillery to afford us the practice?