These different manners of formation are, therefore, reducible to four: the shallow order, where the line is deployed in three ranks; the half-deep order, formed of a line of battalions in columns doubled on the center or in battalion squares; the mixed order, where regiments are partly in line and partly in column; finally, the deep order, composed of heavy columns of battalions deployed one behind the other. [Illustration: Fig. 29.[46] Deployed order in two lines. ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ] The formation into two deployed lines with a reserve was formerly used to a great extent: it is particularly suitable on the defensive. These deployed lines may either be continuous, (Fig. 29,) or checkerwise, or in echelons. [Illustration: Fig. 30. Twelve battalions in columns of attack in two lines, with skirmishers in the intervals. -----...-----...-----...-----...-----...----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- -----...-----...-----...-----...-----...----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ] A more compact order is shown in Fig. 30, where each battalion is formed into a column of attack, being by divisions upon the central division. It is really a line of small columns In the three-rank formation, a battalion with four divisions[47] will have twelve ranks in such a column as shown above: there are in this way too many non-combatants, and the column presents too good a mark for the artillery. To remedy in part these inconveniences, it has been proposed, whenever infantry is employed in columns of attack, to form it in two ranks, to place only three divisions of a battalion one behind the other, and to spread out the fourth as skirmishers in the intervals of the battalions and upon the flanks: when the cavalry charges, these skirmishers may rally behind the other three divisions. (See Fig. 31.) Each battalion would thus have two hundred more men to fire, besides those thrown into the two front ranks from the third. There would be, also, an increase of the whole front. By this arrangement, while having really a depth of but six men, there would be a front of one hundred men, and four hundred men who could discharge their fire-arms, for each battalion. Force and mobility would both be obtained.[48] A battalion of eight hundred men, formed in the ordinary manner in a column of four divisions, has about sixty files in each division, of which the first alone--and only two ranks of that--discharge their pieces. Bach battalion would deliver, therefore, one hundred and twenty shots at a volley, whilst formed in the manner shown in Fig. 31 it would deliver four hundred. [Illustration: Fig. 31.]