.

It was on the logical and practical distinction between these two kinds of
naval object, as we have seen, that the constitution of fleets was based in
the fulness of the sailing period, when maritime wars were nearly incessant
and were shaping the existing distribution of power in the world. During
that period at any rate the dual conception lay at the root of naval
methods and naval policy, and as it is also the logical outcome of the
theory of war, we may safely take it as the basis of our analysis of the
conduct of naval operations.

Practically, of course, we can seldom assert categorically that any
operation of war has but one clearly defined object. A battle-squadron
whose primary function was to secure command was often so placed as to
enable it to exercise control; and, _vice versa_, cruiser lines intended
primarily to exercise control upon the trade routes were regarded as
outposts of the battle-fleet to give it warning of the movements of hostile
squadrons. Thus Cornwallis during his blockade of Brest had sometimes to
loosen his hold in order to cover the arrival of convoys against raiding
squadrons; and thus also when Nelson was asked by Lord Barham for his views
on cruiser patrol lines, he expressed himself as follows: "Ships on this
service would not only prevent the depredations of privateers, but be in
the way to watch any squadron of the enemy should they pass on their
track.... Therefore intelligence will be quickly conveyed, and the enemy
never, I think, lost sight of."[15] Instructions in this sense were issued
by Lord Barham to the commodores concerned. In both cases, it will be seen,
the two classes of operation overlapped. Still for purposes of analysis the
distinction holds good, and is valuable for obtaining a clear view of the
field.

[15] Nelson to Barham, 29 August 1805.

Take, first, the methods of securing command, by which we mean putting it
out of the enemy's power to use effectually the common communications or
materially to interfere with our use of them. We find the means employed
were two: decision by battle, and blockade. Of the two, the first was the
less frequently attainable, but it was the one the British service always
preferred. It was only natural that it should be so, seeing that our normal
position was one of preponderance over our enemy, and so long as the policy
of preponderance is maintained, the chances are the preference will also be
maintained.

But further th