The severest test of discipline is for a skirmish line to rise and rush forward under an effective hostile fire. This movement had best be executed with precision and energy even during peace exercises. The formation and manner of execution must become second nature to the soldier, like a movement of the manual of arms, which he retains during his entire military service, and a knowledge of which he brings with him when called to the colors during mobilization. The example set by advancing leaders and the arrival of reinforcements, which move forward through the firing line, have been found to be the most effective means of carrying a skirmish line forward. The critical moment occurs when the men rise and prepare to rush forward, for an unsubdued enemy will be desirous to prevent, by increasing his fire, any attempt to advance. The fire support afforded by neighboring detachments would seem to have a conditional value only; for, being themselves under fire, the skirmishers of these detachments cannot be expected to divert their fire from the opponent previously fired upon, to an enemy by whom they themselves are not threatened. In oblique fire, the rifles, on account of their short barrel, interfere with neighboring ones, and, in addition, expose the men advancing on the flanks to the danger of being hit by the fire of their comrades. The fire support is, therefore, restricted to hindering the hostile skirmishers directly opposite from firing on the advancing unit. When the terrain is favorable, infantry and machine guns should not hesitate to fire over the heads of their own skirmishers. The coöperation of artillery will, in any case, be of great value, and infantry will have to select those moments for advancing when the defender is driven under cover by the hail of shot.