=Departure of the Second Echelon= (Supporting Companies). When the first echelon, or assaulting companies, have crossed “No Man’s Land,” the battalion commander usually launches the second echelon, or supporting companies. By this time, the battalion commander will have an impression of the assault, and the distance which separates the two echelons is at this moment the one usually required (200 to 300 yards). In order to avoid the enemy’s barrage and to profit by any lull in his fire, the battalion commander chooses the exact moment for the departure of the second echelon. =Advance of the Reserves.= As soon as all the waves of the assaulting battalion have penetrated the enemy’s position, the reserve battalions of the regiment leave their _places d’armes_ and move forward through boyaux to the first parallels of departure. In this position they await the order of the colonel to advance into the enemy’s position to join the combat for its conquest. The colonel awaits the first report from his assaulting battalion before giving the order for the advance of the reserves. III. Fighting in the Interior of the Position and Exploitation =Principle of the Fighting.= The fundamental principle of the fighting in the interior of the position is that each attacking unit from the division down to the battalion receives a definite objective. This objective is usually an area containing the lines of the hostile position with precise flanking limits. The farthest line in the objective area must be gained by the units at all costs. Beyond this last objective, strong reconnaissance parties and patrols are sent to keep contact with the enemy. Usually the attacking regiments, which carry out the struggle in the interior of the position, are assigned the mission to capture the third or covering line of the artillery. The continuation of the struggle beyond this line and the capturing of the enemy’s guns is what is called “the tactical exploitation of the success.” The troops that carry out this operation are the reserves of the division held out for this particular purpose. The plan of battle does not include orders for this action. =Details of the Interior Fighting.= Let us follow an attacking regiment in its progress in the interior of a hostile position, and consider the use of the different echelons of which it is composed: assaulting companies, reinforcing companies, and reserves.