When in the middle of the last century, especially in the theatre of war in which Frederick II. was engaged, generals began to look upon movement as a principle belonging to fighting, and to think of gaining the victory by the effect of unexpected movements, the want of an organised order of battle caused the most complicated and laborious evolutions on a march. In carrying out a movement near the enemy, an army ought to be always ready to fight; but at that time they were never ready to fight unless the whole army was collectively present, because nothing less than the army constituted a complete whole. In a march to a flank, the second line, in order to be always at the regulated distance, that is about a quarter of a mile from the first, had to march up hill and down dale, which demanded immense exertion, as well as a great stock of local knowledge; for where can one find two good roads running parallel at a distance of a quarter of a mile from each other? The cavalry on the wings had to encounter the same difficulties when the march was direct to the front. There was other difficulty with the artillery, which required a road for itself, protected by infantry; for the lines of infantry required to be continuous lines, and the artillery increased the length of their already long trailing columns still more, and threw all their regulated distances into disorder. It is only necessary to read the dispositions for marches in Tempelhof’s History of the Seven Years’ War, to be satisfied of all these incidents and of the restraints thus imposed on the action of war. But since then the modern art of war has subdivided armies on a regular principle, so that each of the principal parts forms in itself a complete whole, of small proportions, but capable of acting in battle precisely like the great whole, except in one respect, which is, that the duration of its action must be shorter. The consequence of this change is, that even when it is intended that the whole force should take part in a battle, it is no longer necessary to have the columns so close to each other that they may unite before the commencement of the combat; it is sufficient now if the concentration takes place in the course of the action.