A similar system prevailed in the colonial areas, but there the naval defence consisted normally of cruiser squadrons stiffened with one or two ships-of-the-line mainly for the purpose of carrying the flag. They were only occupied by battle-squadrons when the enemy threatened operations with a similar force. The minor or interior defence against local privateers was to a large extent local; that is, the great part of the flotilla was furnished by sloops built or hired on the spot, as being best adapted for the service.
Focal points were not then so numerous as they have become since the development of the Far Eastern trade. The most important of them, the Straits of Gibraltar, was treated as a defended area. From the point of view of commerce-protection it was held by the Mediterranean squadron. By keeping watch on Toulon that squadron covered not only the Straits, but also the focal points within the sea. It too had its extended divisions, sometimes as many as four, one about the approaches to Leghorn, one in the Adriatic, a third at Malta, and the fourth at Gibraltar. In cases of war with Spain the latter was very strong, so as to secure the focal area against Cartagena and Cadiz. On one occasion indeed, in 1804-5, as we have seen, it was constituted for a short time an independent area with a special squadron. But in any case the Gibraltar area had its own internal flotilla guard under the direction of the port admiral as a defence against local privateers and pirates.
The general theory of these defended terminal and focal areas, it will be seen, was to hold in force those waters which converging trade made most fertile, and which therefore furnished an adequate field for the operations of raiding squadrons. In spite of the elaborate defensive system, such squadrons might, and sometimes did, intrude by surprise or stealth, and were then able to set at defiance both convoy escorts and the cruiser outposts. But, as experience proved, the system of terminal defence by battle-squadrons made it impossible for such raiding squadrons to remain long enough on the ground to cause any serious interruption or to do serious harm. It was only by a regular fleet of superior strength that the system could be broken down. In other words, the defence could only fall when our means of local control was destroyed by battle.