1st. Formerly the line of battle for infantry was very generally that of two deployed lines of troops, as shown in Fig. 26. But reason and experience have demonstrated that infantry in this thin or light order, can only move very slowly; that in attempting rapid movements it breaks and exhibits great and dangerous undulations, and would be easily pierced through by troops of a deeper order. Hence it is that the light formation is only proper when the infantry is to make use of its fire, and to remain almost stationary. 2d. If the formation of a line of battalions in columns of attack be employed, the depth and mobility will depend upon the organization or habitual formation of this arm. In our service a battalion is supposed to be composed of ten companies, each formed in three ranks. The two flank companies are designed for tirailleurs. This would give a column of four divisions, and consequently twelve files deep; and as only two of these files could employ their fire, there would be much too large a portion of non-combatants exposed to the enemy's artillery. In practice, however, we employ the two-rank formation, which, if the flank companies be detached, would give a column of attack eight files in depth, which is not objectionable. If however, the flank companies should be present in the battalion, the depth of the column would still be ten files. In the French service, each battalion is composed of four divisions, formed in either two or three ranks. The two-rank formation is the one habitually employed. If all the companies be present, and the formation in three ranks, the depth of column will be twelve files; if in two ranks the depth will be eight, files. If the flank companies be detached, the depth of column will be, for three ranks nine files, and for two ranks six files. (Figs. 27 and 28.) In the Russian service each, battalion has four divisions of three ranks each. But the third rank is employed as tirailleurs, which gives a depth of column of eight files. The employment of the third rank for tirailleurs is deemed objectionable on account of the difficulty of rallying them on the column. For this reason, the best authorities prefer detaching an entire division of two companies. The formation of squares is exceedingly effective in an open country, and against an enemy who is superior in cavalry. Formerly very large squares were employed, but they are now formed either by regiment or by battalion. The former are deemed best for the defensive, and the latter for offensive movements. The manner of arranging these is shown in Figure 29.