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.

Again, if we are greatly inferior to the enemy in cavalry, our own
cavalry will have to keep itself within our infantry lines; and the
consequence will be that the enemy will obtain control of the entire
country around us, and so deprive us of all the supplies it contains.

As, besides this, cavalry is absolutely necessary for the protection of
convoys, and, from its celerity of movement, is the kind of force best
fitted for guarding our communications, it is evident that the
subsistence of an army is dependent, to a great extent, upon this arm.

From what has been said in relation to the three arms, it is evident--

1. That ARTILLERY, within the range of its fire, is powerful in
preventing the enemy's approach to it; but, only to a limited extent,
can pursue and drive the enemy from his position; and that its function
is, therefore, mainly DEFENSIVE.

2. That CAVALRY, by the impetuosity of its charge, is peculiarly fit for
driving the enemy from his position; but, remaining in position itself,
has but feeble power to prevent the enemy's approaching it; and this,
only by its carbine and pistol fire, which is far from effective; and
that its function is, therefore, mainly OFFENSIVE.

3. That INFANTRY has great power, both in keeping the enemy at a
distance by its fire and in driving him from his position with the
bayonet; and that this arm is, therefore, both OFFENSIVE and DEFENSIVE.

4. That although artillery is mainly a defensive arm, it plays an
important offensive part in the powerful assistance it renders to
infantry, in shattering and disorganizing the enemy's masses; thereby
opening the way for our attacking columns.

5. That although cavalry is mainly an offensive arm, its defensive value
is also very great in the p