In a few days a powerful artillery had enabled a heroic infantry (fighting under the eye of the American General Pershing) to overcome the resistance of an enemy defending his ground with a force of about nine divisions. This operation justifies once more our assertion that it is impossible to construct works that are absolutely impregnable to gun-fire. To give an idea of the morale of the French, we can do no better than to cite a passage from a letter, written at the Front on October 6th, which we have just received from a young artillery officer. “Watch the communiqués that will be issued on or about the 20th day of October. We are preparing for the Boches a song and dance that they will not forget.” =2. General plan of an intrenchment system.= The description we give hereafter of the organization of the lines is, of course, like the following diagram, purely explanatory and illustrative. [Illustration: South-east of Ailles February 10, 1917--2.30 P.M.] It is intended to set forth the principles governing trench-construction and to give a general idea of a system of field fortifications. Such a system is subject to the exigencies of local topography, and it is therefore impossible to state exact measurements and distances for the broad outlines of the plan. Thus one could formulate no law to fix the distance which should separate the different lines of an intrenched position; and even with regard to the breadth of the interval between two trenches of the same line, one can scarcely be more precise; since, however essential it may be in theory to make it broad enough to prevent a single shell from doing damage to both trenches, in practice the configuration of the ground does not always permit of such a precaution. The plotting-out of the trenches is of very great importance. They must be made in such a manner that they will not be exposed to an enfilading fire of the enemy’s guns, and will be strong enough to oppose the greatest resistance to attack. Too long and too straight lines are generally avoided. The usual custom is to reproduce the ground plan of a bastion, with alternating salients and re-entrants, a disposition which permits flank firing across the front of the trench (Fig. 1). The re-entrants are frequently additionally fortified so as to render them insurmountable to assault, so that the defenders need occupy the salients only. Advanced trenches exposed to intense bombardment can thus be defended with a smaller number of men. [Illustration: _FIG. 1_] The inside of the trenches is provided at short intervals with _pare-éclats_, or shell-screens, consisting of buttresses of earth supported by _clayonnages_, or wattle-work, which are intended to limit as much as possible the radius of action of a bursting shell to a single section of trench (Fig. 2).