=78.= =Plan of Attack.=--By this time the reconnoissances and surveys should be so far advanced and so thoroughly checked up that the chief engineer will have been able to make, upon a large scale, a map of the place and its surroundings with considerable accuracy, and to locate upon it the proposed position of the first and second parallels, the approaches, and the batteries of the second artillery position. This map, with the accompanying memoirs, makes up the “_plan of attack_,” which, when approved by the commanding general, serves as a working plan for the prosecution of the siege, and is continually corrected and added to as the siege progresses. This map should be made in duplicate at least, and for accuracy in the history of the siege should be corrected so far as possible by redrawing or tracing, instead of by erasures. =79.= =The First Parallel.=--The first parallel (Pl. VIII, Figs. 80 and 81) serves as an intrenchment for the troops who protect the second artillery position and who cover the workmen driving the approaches. It also affords a covered communication between the different lines of approaches. Its length must be sufficient to cover all the batteries of the second artillery position and protect their flanks; it must therefore extend beyond the batteries which enfilade those faces of the fronts attacked whose prolongations fall furthest out. Its flanks are usually more or less refused, and terminated by strong earthworks. Emplacements for batteries of field guns are provided at intervals to assist the infantry in repelling sorties. When the length of the parallel is very great, it is sometimes not continuous when first opened, but the portions covering the groups of batteries are first made and are subsequently connected. The ground between them is protected, meanwhile, by a strong fire of small arms, field and other guns. When communications covered by natural screens do not exist between the first parallel, the batteries of the first artillery position, and the parks, approaches are constructed at the same time as the parallel, in sufficient number to give free passage to the troops, guns, and materials. These approaches (Pl. VIII, Figs. 80 and 81), as all others (par. 13), are so directed as not to be enfiladed by the fire of the work, and should be provided with portable or other tramways and cars, passing switches being placed in the returns where needed.