Some of the departures from the principle of the line are rather apparent than real. A reserve is no exception, even when it becomes a whole second, or even third line: for the reserve ex _hypothesi_ is not fighting: when it is wanted to fight it is brought up to the front, and ceases to be in reserve. Foot-soldiers standing on the defensive, especially as against horsemen, present the largest amount of front in the safest way by forming a closed figure, the ring of the Northmen and of the Scots, or the familiar square of modern infantry in the days before the rifle. Nevertheless modifications are liable to be introduced, so to speak, from both sides. The order of battle is deepened, with the idea of giving greater impetus to a charge, from the weight of men behind backing up the front ranks. Epaminondas, using this device unexpectedly at Leuctra, defeated the Spartans, whose superior discipline and physique made them invincible so long as both sides used the same formation. His success led to the adoption of the Macedonian phalanx, and the abandonment of the line for the time being, until the Romans reverted successfully to the natural order. The order of march, for a real journey, cannot well be modified, because roads do not allow it. But for short marches, over open ground, there was much to be gained by massing men more closely together. They could hear orders better, and could be moved in any direction with more ease and precision. Hence arose the column, which is strictly speaking a series of short lines ranged one behind the other, and which, as military evolutions were developed, became the natural formation for manœuvring, as distinguished from fighting. Then obvious convenience would suggest keeping the troops as long as possible in the more handy formation of columns, even on the field of battle. Until the actual shock was impending, it was better to leave them so formed that they could be readily moved if necessary to another part of the field. Until artillery became really effective, the risk of increased loss, from cannon-balls passing through a solid body, instead of a line, was not very serious. Until the bayonet was introduced, the necessity for pikemen and musketeers acting together would tend to make deep formations, which are columns without their mobility, a virtual necessity. Thus in more ways than one column came to be regarded as the ordinary formation, line as the exception. And generals were led by the real convenience of mobility and facility of command, perhaps also by other calculations, to make attacks in column, with or without the intention of extending into line after the enemy's front had been pierced.