To master the borders of a center of resistance on the flank of troops that have pushed into the intervals. Eventually they may at certain points receive the order to throw back a counter-offensive and to pursue. When the troops of the second line arrive in the proximity of the troops of the first line who have been stopped, there should be no idea of maneuvering nor of consultation, but as in the case of the first enemy trench, they must carry through _the assault without hesitation_. Two cases are presented according to the distance that separates the fractions of the halted first line from the hostile resistance: 1. Distance less than 200 metres: If the stopped first line can maintain itself at the limit of its progression, it is generally not in an open field. Its line will serve as a parallel of departure for the units of the second line. These units at first try to reach the line of shelter where they will be formed. Their assaulting formation results from the march formation, and the waves will be composed of half companies. The first wave rushes out of cover at the double to at least half the distance and opens fire; fire being opened, the second wave rushes _in line_ and carries along the first. Here the firing cannot be prevented, as artillery support, now faulty, has to be replaced by rifle fire, to which is joined the fire of machine guns and light cannon, which alone can make possible so fearful an assault. 2. Distance more than 200 metres—Progression and Assault: The new difficulty is to build up at assaulting distance from the enemy a line of assault in a sort of parallel of departure. To arrive at assaulting distance, advance by thin lines formed by halving the skirmish lines already deployed; these lines, at least 100 metres apart, advance successively by alternate rushes, then unite on the line designated as the starting point for the assault. A natural parallel of departure may exist or may partially exist, or it may not exist at all. In the second case, the line of shelters must be adapted, and in the third case it must be created in order to be able to stay a few moments at a short distance from the enemy without being destroyed. To facilitate this extremely difficult and dangerous construction, it is a good thing to have each man fill a sand bag at the last shelter and put in some stones, which, while not bulky, stop the bullets. Each man makes his rushes with his sand bag, which protects him partially during the halts. Having reached the line fixed upon for the parallel, this sand bag serves him as a cover, which he has only to complete rapidly. Each man then enlarges his shelter so as to accommodate near comrades. The first wave, reformed at the assaulting distance, makes the assault as before. At times, the losses and the confusion of units may lead to an assault by entire companies. The second and third waves follow and imitate the movements of the first.