THE INFANTRY OF THE LEGION.
§ I. The chief strength of the Roman army was the legionary infantry. The cavalry was merely auxiliary to this in field operations and was comparatively weak in number. The engines (corresponding to our artillery) were used in siege operations, but very little in the field. The heavy infantry furnished by the allies (auxilia), though generally organized and trained after the Roman model, were rather used to make a show of force than for much important service in battle.
The European armies of the middle ages were composed almost wholly of cavalry; the individual horseman being encased in heavy armor and equipped with sword, spear and battle-axe. In modern armies the infantry is again the main arm of the service. Unlike the Roman legions, however, our infantry is greatly strengthened by a powerful field artillery. No army of mere cavalry can be very effective unless in partial and temporary operations.
Ro. I, § II, p. 80,81.
§ 2. The tactical unit of the Roman infantry was the legion (legio). Cæsar had under his command at different times a varying number of legions.
A tactical unit may be'defined as a body of troops under a single command, by a combination of several of which a higher unit is formed. Thus in the army of the United States, the tactical unit of the army is the corps; each corps should contain three divisions; each division, three brigades; each brigade, four regiments (or battalions); each
U §§ 365, 55I.718,748.