Small bridges are constructed for the passage of the parallels by the reserves. It is not necessary that the shelter accommodations be numerous, especially in the first line, because the assaulting troops are brought in only a few days before the attack. =The Execution of the Works.= The second part of the plan of ground disposition contains the details of the execution of the works for the preparation of the ground previous to the attack. This part consists of; 1. Emergency works (necessary to the assault). Observatories and command posts. The first two parallels of departure for each battalion. If none need be constructed, the defensive lines used for this purpose are designated. Secondary boyaux between parallels, one for each company. Entrance and evacuation boyaux. Ammunition depots and water points. Dressing stations. If there is more time, the following are constructed: The third and fourth parallels. Telephone wires and material brought up. Bridges for crossing the parallels. 2. Time of duration of the execution of the works. This may vary from three to twelve days, or even more, depending upon circumstances. 3. Division of labor. This depends upon the number of special working parties at your disposal. A whole division may be assigned for this work, but it is not the division that will make the attack. 4. Tools. The tools required for this work are requisitioned from the headquarters of the attacking army. 5. Ammunition depots. Cartridges, hand grenades, and signal rockets. 6. Ammunition depots. Sandbags and logs. 7. Transportation of supplies. Special means of transportation besides the usual ones, railroads, motor trucks, mules, horses, etc. Artillery Preparation During the time employed in preparing the ground for the attack, the artillery executes the preliminary bombardment. This comprehends three kinds of fire. 1. =Counter-Battery Fire.= A certain part of the artillery is detailed to destroy the hostile batteries or, if this is not possible, to neutralize them. This result is obtained by methodical fire on precise targets. Each battery or group of batteries is assigned certain emplacements to destroy. Counter-battery fire is long-winded work and is begun several days or even weeks before the attack. If the hostile batteries are not destroyed before the time of attack, they must be neutralized at this moment by violent shelling by all the batteries disposed for this purpose, with shrapnel and other special shells. This counter-battery action will hinder the hostile artillery from executing defensive fire, barrage, preventive fire, counter-preparation fire. It is carried out by special groups of heavy and light artillery under control of the general.