An important consideration in determining the necessary composition of a navy is the subdivision of fighting power into offensive and defensive. The latter is represented chiefly by armor, the former by guns; although other factors contribute to both. The relative importance of the two depends upon no mere opinion of the writer, but upon a consensus of authority practically unanimous, and which, therefore, demands no argument, but simple statement. Offensive action—not defensive—determines the issues of war. "The best defence against the enemy's fire is a rapid fire from our own guns," was a pithy phrase of our Admiral Farragut; and in no mere punning sense it may be added that it is for this reason that the rapid-fire gun of the present day made such big strides in professional favor, the instant it was brought to the test of battle. The rapid-fire gun is smaller than the great cannon mounted in the turrets; but, while the latter have their proper usefulness, the immensely larger number of projectiles fired in a given time, and valid against the target presented to them, makes the rapid-fire battery a much stronger weapon, offensively, than the slow-acting giants. Here is the great defect of the monitor, properly so-called; that is, the low-freeboard monitor. Defensively, the monitor is very strong; offensively, judged by present-day standards, it is weak, possessing the heavy cannon, but deficient in rapid fire. Consequently, its usefulness is limited chiefly to work against fortifications,—a target exceptional in resistance, and rarely a proper object for naval attack. It is the opinion of the writer that no more monitors should be built, except as accessory to the defence of those harbors where submarine mines cannot be depended upon,—as at San Francisco and Puget Sound. It should be added that the monitor at sea rolls twice as rapidly as the battleship, which injuriously affects accuracy of aim; that is, offensive power.
The general principle of the decisive superiority of offensive power over defensive is applicable throughout,—to the operations of a war, to the design of a battleship, to the scheme of building a whole navy. It is to the erroneous belief in mere defence that we owe much of the faith in the monitor, and some of the insistence upon armor; while the cry that went up for local naval defence along our coast, when war threatened in the spring of 1898, showed an ignorance of the first principles of warfare, which, if not resisted, would have left us impotent even before Spain.
Brief mention only can be given to the other classes of vessels needed by the navy. Concerning them, one general remark must be made. They are subsidiary to the fighting fleet, and represent rather that subdivision of a whole navy which is opposed to the idea of concentration, upon which the battleship rests. As already noted, a built ship cannot be divided; therefore, battleships must be supplemented by weaker or smaller vessels, to perform numerous detached and often petty services.
From this characteristic of detachment—often singly—important engagements will rarely be fought by these smaller vessels. Therefore, in them fighting power declines in relative importance, and speed, to perform their missions, increases in proportion. As their essential use is not to remain at the centres, but to move about, they are called generically cruisers, from the French word croiser,—to cross. They cross back and forth, they rove the sea,—despatch boats, lookouts, scouts, or raiders. They are the cavalry of the fleet.
Prominent among these in modern navies is the so-called "armored" cruiser,—a type to which belonged the four principal vessels of Cervera's squadron. The name itself is interesting, as indicating the inveterate tendency of mankind to straddle,—the reluctance to choose one of two opposite things, and frankly to give up the other. Armor, being an element of fighting power, belongs properly to the battleship rather than the cruiser; and in the latter, if the weight spent in armor detracts from speed or coal endurance, it contravenes the leading idea of a cruiser,—mobility. But, while the name is incongruous, the type has its place as an armored vessel, though not as a cruiser. In our service at least—where it is represented by the New York and the Brooklyn—it is practically a second-class battleship, in which weight taken from fighting power is given to enginery and to speed. The advantage arising from this is purely tactical; that is, it comes into play only when in touch with the enemy. The armored cruiser belongs with the fleet, therefore her superior speed does not tell in making passages; but when fleets are in presence, or in the relative conditions of chase and pursuit, there is an advantage in being able to throw to the front, rear, or flanks, vessels which on a pinch can either fight or fly. This, be it noted in passing, is no new thing, but as old as naval history. A squadron of fast battleships of the day, thrown to the front of a fleet to harass the flanks of the enemy, is a commonplace of naval tactics, alike of galleys and sailing ships. Off Santiago, the New York and Brooklyn were, by Admiral Sampson, placed on the flanks of his squadron. Whichever way Cervera turned he would find a vessel of speed and fighting power equal to those of his own ships. Though unequal in fighting power to a first-class battleship, many circumstances may arise which would justify the armored cruiser in engaging one, provided her own fleet was in supporting distance. From their hybrid type, and from the exceptional circumstances under which they can be used, the tonnage put into these vessels should be but a small percentage of that given to the battle fleet, to which, and not to the cruisers, they really belong.
Concerning all other cruisers, mobility, represented in speed and coal endurance, is the chief requisite. Notwithstanding occasional aberrations in the past, the development of the cruiser classes may be safely entrusted by the public to the technical experts; provided it be left to naval officers, military men, to say what qualities should predominate. Moreover, as such vessels generally act singly, it is of less importance that they vary much in type, and the need of subdivision carries with it that of numerous sizes; but battleships, including armored cruisers, are meant to work together, and insistence should be made upon homogeneousness, especially in manœuvring qualities.
To sum up: the attention of the public should be centred upon the armored fleet, to which the bulk of expenditure should be devoted; the monitor, pure and simple,—save for very exceptional uses,—should be eliminated; the development of the true cruiser,—not armored,—both in type and in numbers, does not require great interest of the public; much of the duties of this class, also, can be discharged fairly well by purchased vessels, although such will never have the proportion of fighting power which every type of ship of war should possess. As a rule, it is undesirable that a military force, land or sea, should have to retreat before one of equal size, as auxiliary cruisers often would.