a heavy fire so as to make it difficult for the enemy to gain the fire superiority. The principles governing the moment for opening fire have already been discussed (pp. 147 and 154 supra).
The enemy must be prevented from gaining the superiority of fire. This should be accomplished by concentrating the fire from a large number of rifles upon the parts of the enemy's force in motion. The defender should make the most of the advantage which his preparedness gives him. The attacker's firing line with its supports forms the target. A departure from this rule is in order, in the case of a French assailant, as the latter places the bulk of his force in the reserves and not in the firing line. It will frequently be practicable for the defender to discontinue his fire and to take cover when the assailant lies down and fires; but, while under cover, everything should be prepared for resuming the fire when the enemy rises to continue his advance (p. 156 supra).
If it has been found impossible to prevent the enemy from reaching the extreme limit of short ranges, the commander must decide whether to continue the fight until a decision is reached, or whether to break off the action.
When the opponent has entered the zone of short ranges, it will be too late for the defender to retire, unless the terrain in rear of the position is especially favorable, or other troops can take a hand in the fight to cover the withdrawal. The onrushing assailant is received with accelerated fire; the defender fixes bayonets, determined to risk a fight at close quarters. "The defender who does not fix bayonets is already casting furtive glances towards the best line of retreat."
While repulsing an assault, it would be a good plan for the defender to step upon the rear wall of the trench so that the latter would become an obstacle for the attacker. But this scheme can only be employed when the troops are completely in hand.
While the fire of the defender is increased to the utmost intensity by the entrance into the fight of all the supports, the
