Before dealing with this, the most complex aspect of the question, it will be well to dismiss attack. From the strategical point of view its principles differ not at all from those already laid down for active resistance of invasion. Whether the expedition that threatens us be small or of invasion strength, the cardinal rule has always been that the transports and not the escort must be the primary objective of the fleet. The escort, according to the old practice, must be turned or contained, but never treated as a primary objective unless both turning and containing prove to be impracticable. It is needless to repeat the words of the old masters in which this principle lies embalmed. It is seldom that we find a rule of naval strategy laid down in precise technical terms, but this one is an exception. In the old squadronal instructions, "The transports of the enemy are to be your principal object," became something like a common form.
Nor did this rule apply only to cases where the transports were protected by a mere escort. It held good even in the exceptional cases where the military force was accompanied or guarded by the whole available battle strength of the enemy. We have seen how in 1744 Norris was prepared to follow the French transports if necessary with his whole force, and how in 1798 Nelson organised his fleet in such a way as to contain rather than destroy the enemy's battle-squadron, so that he might provide for an overwhelming attack upon the transports.
Exceptions to this as to all strategical rules may be conceived. Conditions might exist in which, if the enemy's battle-fleet accompanied his transports, it would be worth our while, for ulterior objects of our own, to risk the escape of the transports in order to seize the opportunity of destroying the fleet. But even in such a case the distinction would be little more than academical; for our best chance of securing a decisive tactical advantage against the enemy's fleet would usually be to compel it to conform to our movements by threatening an attack on the transports. It is well known that it is in the embarrassment arising from the presence of transports that lies the special weakness of a fleet in charge of them.