The offensive in naval war, as has been said, is the function of the sea-going navy--of the battle-ships, and of the cruisers of various sizes and purposes, including sea-going torpedo-vessels capable of accompanying a fleet, without impeding its movements by their loss of speed or unseaworthiness. Seaworthiness, and reasonable speed under all weather conditions, are qualities necessary to every constituent of a fleet; but, over and above these, the backbone and real power of any navy are the vessels which, by due proportion of defensive and offensive powers, are capable of taking and giving hard knocks. All others are but subservient to these, and exist only for them. What is that strength to be? Ships answering to this description are the _kind_ which make naval strength; what is to be its _degree_? What their number? The answer--a broad formula--is that it must be great enough to take the sea, and to fight, with reasonable chances of success, the largest force likely to be brought against it, as shown by calculations which have been indicated previously. Being, as we claim, and as our past history justifies us in claiming, a nation indisposed to aggression, unwilling to extend our possessions or our interests by war, the measure of strength we set ourselves depends, necessarily, not upon our projects of aggrandizement, but upon the disposition of others to thwart what we consider our reasonable policy, which they may not so consider. When they resist, what force can they bring against us? That force must be naval; we have no exposed point upon which land operations, decisive in character, can be directed. This is the kind of the hostile force to be apprehended. What may its size be? There is the measure of our needed strength. The calculation may be intricate, the conclusion only approximate and probable, but it is the nearest reply we can reach. So many ships of such and such sizes, so many guns, so much ammunition--in short, so much naval material. In the material provisions that have been summarized under the two chief heads of defence and offence--in coast defence under its three principal requirements, guns, lines of stationary torpedoes, and torpedo-boats, and in a navy able to keep the sea in the presence of a probable enemy--consist what may be called most accurately preparations for war. In so far as the United States is short in them, she is at the mercy of an enemy whose naval strength is greater than that of her own available navy. If her navy cannot keep the enemy off the coast, blockade at least is possible. If, in addition, there are no harbor torpedo-boats, blockade is easy. If, further, guns and torpedo lines are deficient, bombardment comes within the range of possibility, and may reach even the point of entire feasibility. There will be no time for preparation after war begins.