Cavalry of the line, to produce its decisive effects, must be used in heavy masses. In the beginning of the Napoleonic wars, the French cavalry was distributed among the divisions. Napoleon's subsequent experience led him to give it more concentration, by uniting in one mass all the cavalry belonging to each army corps; and, finally, these masses were again concentrated into independent cavalry corps; leaving to each army corps only cavalry enough to guard it. 8. For tactical operations in the field, cavalry insufficient in number is _scarcely better than none at all_, as it can never show itself in presence of the enemy's cavalry, which would immediately outflank and destroy it, and must keep close behind its infantry. At the opening of Napoleon's campaign of 1813, he had but very little cavalry to oppose to the overwhelming masses of this arm possessed by the Allies. In consequence of this, he could make no use of it whatever; and the tactical results of the battles of Lutzen and Bautzen were far inferior to those habitually obtained in his former victories, and were purchased with much greater loss. 9. Small bodies of cavalry threatened by the enemy's cavalry in greatly superior force, may sometimes be saved by taking refuge _in an infantry square_, as practised by Napoleon at the battle of the Pyramids. 10. Cavalry should _remain masked_ as long as possible; for it produces most effect when its position and movements are hidden, so that a strong force may suddenly be brought upon a weak point. For this reason, a flat, open country is less favorable for this arm than plains with undulations, hills with gentle slopes, woods, villages, and farms; all these being so many facilities for screening cavalry from view. 11. Cavalry should never be brought to the front, _except to engage_. It is unfortunate when the ground is such as to prevent this; for cavalry, compelled to remain inactive under fire, is in great danger of becoming demoralized. 12. As to the _ground_: (1.) Cavalry must not rest its flank on a wood, a village, or other cover for an enemy, till it has been occupied by our own troops. If compelled to do so, it should send out patrols to reconnoitre and observe. Its position is no longer tenable from the moment the enemy appears within striking distance on its flank. (2.) It must not be posted on the very ground it is to defend, but in rear of it; as it acts effectively only by its charge. Attacking cavalry must have favorable ground in front; defending cavalry, in rear. An obstacle in either case may be fatal. IV.--Its Supports. 1. The flanks of cavalry lines or columns are always exposed. They should, therefore, be protected by _supports_ of light cavalry, which can act promptly and swiftly. When behind a line, these supports should be usually in open column, so as to be able to wheel, without a moment's delay, into line.