(2.) Since the introduction of the new rifled arms, exposing cavalry masses to a deadly fire at far greater distances than ever before known, a fire often reaching to the reserves, it seemed doubtful whether the manoeuvring and charging in heavy, compact masses, which formerly rendered cavalry of the line so formidable, would any longer be practicable. (3.) The comparative cost of this kind of force is so great, that, if it had been raised and kept up on the scale required, the expense of this war, enormous as it has been, would have been vastly augmented. Three years are required for the thorough training and instruction of the men and horses; so that it would not have been until the fourth year of the war that we could begin, even, to reap the fruits of so enormous an outlay. 5. But to carry on any war successfully, what is needed, and is, in fact, indispensable, is an ample force of light cavalry, of a kind requiring comparatively but little time and training to fit it for the various and important duties devolving upon it in the field, and therefore far less expensive than cavalry of the line; and having all the discipline of this latter kind of force, though wanting its perfection of manoeuvre. Every army, or considerable detachment, must have enough of this kind of force with it to furnish what is requisite for Outpost duty, Patrols offensive and defensive, Escorts to trains, Foraging parties, Reconnoissances, and the various other purposes necessarily incidental to operations in the field; and in marches, all Advanced, Rear, and Flank guards should consist, in part, at least, of cavalry. Finally, this description of force is needed for the performance of those arduous, but most valuable, services often rendered by the quasi-independent bodies called Partisan Corps; services usually requiring great celerity of movement. 6. This kind of force being "the eyes and ears of an army," it often contributes powerfully to the success of strategic operations. In the campaign of 1813, Napoleon complained that, for want of light cavalry, he could get no intelligence of the enemy's movements. So, in the rebel campaign of 1863, culminating at Gettysburg, General Lee attributed his ignorance of our position and movements, which led to the failure of his operations, to his being destitute of this arm; Stuart's cavalry, on which he depended for information, having got too far away from him. In Pope's campaign in 1862, the rebels, by their cavalry raid on Catlett's Station, obtained possession of the commanding general's correspondence, plans, and orders from Washington. On the other hand, whilst keeping us informed of the enemy's movements, an abundant light cavalry, active and well commanded, may be so used as to constitute an impenetrable screen of our own movements from the enemy, as effectual as would be a lofty and impassable mountain range.