Offense therefore dominates, but it does not exclude. The necessity for defense remains obligatory, though subordinate. The two are complementary. It is only in the reversal of _rôles_, by which priority of importance is assigned to the defensive, that ultimate defeat is involved. Nor is this all. Though opposed in idea and separable in method of action, circumstances not infrequently have permitted the union of the two in a single general plan of campaign, which protects at the same time that it attacks. “Fitz James’s blade was sword and shield.” Of this the system of blockades by the British Navy during the Napoleonic wars was a marked example. Thrust up against the ports of France, and lining her coasts, they covered—shielded—the operations of their own commerce and cruisers in every sea; while at the same time, crossing swords, as it were, with the fleets within, ever on guard, ready to attack, should the enemy give an opening by quitting the shelter of his ports, they frustrated his efforts at a combination of his squadrons by which alone he could hope to reverse conditions. All this was defensive; but the same operation cut the sinews of the enemy’s power by depriving him of sea-borne commerce, and promoted the reduction of his colonies. Both these were measures of offense; and both, it may be added, were directed upon the national communications, the sources of national well-being. The means was one, the effect twofold.... [It is shown that, in the case of insular states, offense and defense are often closely combined, home security depending on control of the sea assured by offensive action of the national fleet.—EDITOR.] An insular state, which alone can be purely maritime, therefore contemplates war from a position of antecedent probable superiority from the twofold concentration of its policy; defense and offense being closely identified, and energy, if exerted judiciously, being fixed upon the increase of naval force to the clear subordination of that more narrowly styled military. The conditions tend to minimize the division of effort between offensive and defensive, purpose, and, by greater comparative development of the fleet, to supply a larger margin of disposable numbers in order to constitute a mobile superiority at a particular point of the general field. Such a decisive local superiority at the critical point of action is the chief end of the military art, alike in tactics and strategy. Hence it is clear that an insular state, if attentive to the conditions that should dictate its policy, is inevitably led to possess a superiority in that particular kind of force, the mobility of which enables it most readily to project its power to the more distant quarters of the earth, and also to change its point of application at will with unequalled rapidity.