from the other. Both ideas are
satisfied by occupying the common communications. The strongest form of
attack is the occupation of the enemy's terminals, and the establishment of
a commercial blockade of the ports they contain. But as this operation
usually requires the blockade of an adjacent naval port, it also
constitutes, as a rule, a defensive disposition for our own trade, even
when the enemy's terminal area does not overlap one of our own. In the
occupation of focal areas the two ideas are even more inseparable, since
most, if not all, such areas are on lines of communication that are common.
It will suffice, therefore, to deal with the general aspect of the subject
from the point of view of defence.

It was in conformity with the distinction between fertile and infertile
areas that our old system of trade defence was developed. Broadly speaking,
that system was to hold the terminals in strength, and in important cases
the focal points as well. By means of a battle-squadron with a full
complement of cruisers they were constituted defended areas, or "tracts" as
the old term was, and the trade was regarded as safe when it entered them.
The intervening trade-routes were left as a rule undefended. Thus our home
terminals were held by two battle-squadrons, the Western Squadron at the
mouth of the Channel, and the North Sea or Eastern Squadron with its
headquarters usually in the Downs. To these was added a cruiser squadron on
the Irish station based at Cork, which was sometimes subordinate to the
Western Squadron and sometimes an independent organisation. The area of the
Western Squadron in the French wars extended, as we have seen, over the
whole Bay of Biscay, with the double function, so far as commerce was
concerned, of preventing the issue of raiding squadrons from the enemy's
ports, and acting offensively against his Atlantic trade. That of the North
Sea squadron extended to the mouth of the Baltic and the north-about
passage. Its main function during the great naval coalitions against us was
to check the operations of Dutch squadrons or to prevent the intrusion of
French ones north-about against our Baltic trade. Like the Western
Squadron, it threw out divisions usually located at Yarmouth and Leith for
the protection of our coastwise trade from privateers and sporadic cruisers
acting from ports within the defended area. Similarly, between the Downs
and the Western Squadron was usually one or more smaller squadro