The infantry of the line acts in masses, and, on the field of battle, constitutes the principal fighting force. Its formations and the manner of engaging it have already been discussed under the head of tactics. The importance of infantry is due, in considerable part, to the fact that it can be used everywhere--in mountains or on plains, in woody or open countries, in cities or in fields, on rivers or at sea, in the redoubt or in the attack of the breach; the infantry depends only on itself, whereas the other arms must depend in a considerable degree on the efficiency of their materials and the will and strength of brute force; and when the snows of Russia or the deserts of Egypt deprive their animals of the means of sustenance, they become perfectly useless. Foot-soldiers, in olden times, were armed with a spear and sometimes with a sword, arrows, lance, and sling. At present they are armed with a gun and bayonet, and sometimes with a sword. In some European services, a few of the foot-soldiers are armed with a pike. Some of the light troops used as sharpshooters carry the rifle, but this weapon is useless for the great body of infantry. The short-sword is more useful as an instrument for cutting branches, wood, &c., than for actual fighting. The infantry have no defensive covering, or at least very little. The helmet or cap serves to protect the head, and the shoulders are somewhat defended by epaulets. It has often been proposed in modern times to restore the ancient defensive armor of the foot-soldier; but this would be worse than useless against fire-arms, and moreover would destroy the efficiency of these troops by impeding their movements. The strength of this arm depends greatly upon its discipline; for if calm and firm, a mass of infantry in column or in square is almost impenetrable. The bayonet was introduced by Vauban in the wars of Louis XIV., and after the years 1703 and '4, the pike was totally suppressed in the French army. This measure was warmly opposed by Marshal Montesquieu, and the question was discussed by him and Marshal Vauban with an ability and learning worthy of these great men. The arguments of Vauban were deemed most conclusive, and his project was adopted by the king. This question has been agitated by military writers in more recent times, Puysegur advocating the musket, and Folard and Lloyd contending in favor of restoring the pike. Even in our own service, so late as the war of 1812, a distinguished general of the army strongly urged the use of the pike, and the fifteenth (and perhaps another regiment) was armed and equipped in part as _pikemen_; but experience soon proved the absurdity of the project.