After a few of the successive lines have reached the new position, they form a dense enough target to draw artillery fire. For this reason the position of the new line should be one affording cover from artillery fire if possible; if not, men must get cover by digging to protect at least their heads from shrapnel. Head cover and the pack will give them protection from being killed if not from being wounded.
If the advance in this manner must be for three or four thousand yards and the enemy has advanced posts or is likely to make an infantry counter attack, the advance over this whole distance can not be made at once but must be made by steps, growing shorter as you approach the enemy’s position.
Artillery sweeping fire
The artillery will often sweep with fire an area being crossed by infantry. This is done by increasing or decreasing the range after each shot until the entire area is beaten. If this process be repeated often enough the artillery will get anything within this area not under cover. But this does not change the average number of shrapnel required to get a man nor does it render advisable a great expenditure of ammunition for meager results.
Infantry encountering this kind of fire should, as it approaches, lie down and get what cover is available and, after the storm has passed, move on.
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.
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.