The Evolution of Naval Armament

by Frederick Leslie Robertson

The type having been decided for each individual vessel, there remained the question of the disposition of the armament.

Two main considerations guided the evolution of the ironclads of this period in respect of the disposition of their guns: one mainly tactical, the other mainly constructive. It appears probable that, from the date of Trafalgar onward, the limitations of merely broadside fire had been realized; that the end-on attack, such as had obtained in the supreme actions fought by Nelson and Rodney, had shown the weakness of the broadside ship in ahead fire and had made obvious the anomaly that, in all ships-of-the-line, the course of the ship, the direction in which the attack was made, was the very direction in which gunfire was least powerful, if not altogether non-existent. With the coming of steam and the consequent growth of the ram and ramming tactics, this anomaly was more and more apparent; and from the Warrior onwards each new type presented an enhanced effort to provide, particularly, ahead fire. The growth of the gun materially assisted this effort. Ahead fire increased, between the years 1860 and 1880, from zero to a large proportion of the total fire. The broadside ship was for a time abandoned.

The constructive consideration was the requirement of a protected armament capable of the maximum effective fire in all directions. In the first half of the century an increased effectiveness had been obtained, with the old-fashioned truck guns, by adaptation of the ports or by use of specially designed carriages, to permit of as large an arc of training as possible. Even so the arc through which guns could be fired was small, and in the case of the 68-pounder of the Warrior was only thirty degrees before and abaft the beam. The demand for greater utility was emphasized when, with the increase in size of the unit gun, the number of pieces carried by each ship was diminished.

How, then, having regard to these two considerations, should a warship’s guns be disposed? Various methods were adopted. In the first instance, it was seen to be possible to augment the ahead fire of a ship, and to give a wide sweep of training to some of her guns, by indenting the sides; by so shaping the ship’s side-plating as to allow guns mounted in the forward part to fire in the direction of the ship’s longitudinal axis. At first, slight use was made of this method: with the fine lines given to iron ships it appeared practicable in only a small degree. Moreover, it was objected to as causing a “funnelling” effect to the path of fragments of enemy shell or shot; it was found that shrapnel shell, fired at indented embrasures at Shoebury, broke up, and the number of balls which entered the portholes was ten times the number which entered similar portholes on a straight side. But, after the Minotaur class, less length and greater beam were given to ships, and recessed ports and indented sides therefore became more feasible.

As guns increased in weight and individual importance the advantages of concentration became apparent. It was now undoubtedly desirable to protect all the guns; yet, if they had been strung out along the whole length of the ship, the weight, both of the guns and their protective armour, would prove to be an excessive burden to the ship. Hence the advantage of the central battery. By concentrating the guns into a central area, an armoured box amidships, the weight of armour necessary to protect them could be kept within reasonable limits, protection was afforded not only to the guns but to the vital parts of the ship, while at the same time the extremities were left lightly loaded. The complete water-line belt of armour was retained, but, both in the French and in the English navy, the system of complete protection as embodied in the Gloire and Warrior was given up.

This device of the central battery was at first used solely for broadside guns. But the desire for ahead fire from behind armour soon caused the adaptation of the battery to allow it. Ports were cut in the two transverse bulkheads, the ship’s sides were indented, suitable gun-mountings were provided whereby some of the battery guns could be shifted from one porthole to another; and in this way it was secured that a fair proportion of the armament could be fired either on the beam or parallel with the keel-line of the ship. A power of offence was given in all directions, and no “point of impunity” existed.

Ingenious were the arrangements resorted to, to obtain the maximum effect from the new medium-sized artillery which superseded the original truck-guns of the Warrior and former warships. The armoured boxes, instead of being made with their sides respectively parallel, and at right angles, to the sides of the ship, were sometimes set diagonally, with their sides at forty-five degrees with fore-and-aft. Sometimes they were octagonal, sometimes with curved bulkheads, sometimes two batteries were superposed one on the other; but always the desire was to utilize each gun over as large as possible an arc of fire, and always the tendency was to augment the ahead fire. The central battery formed a powerful citadel covering the whole beam of the ship amidships. The guns of this citadel, by the power of manœuvring given by the adoption of twin-screw propelling machinery, could, it was argued, be brought to bear in any direction desired. Of all directions, “right ahead” was considered to be of the greatest importance. End-on fighting, it was assumed, would always be resorted to in future; and it was the power of keeping the ship end-on to the enemy which was the great military advantage conferred by twin screws.

A further step in the direction of giving to each gun a large arc of fire was taken in the introduction of the sponson. By means of this circular platform, projecting from the vessel’s side, a gun could be carried so as to fire through an arc of 180 degrees. The same system obtained largely in the French ships of this period; by mounting guns in overhung circular turntables, one at each corner of the central battery en caponière, a large effective arc was obtained for them.

Only one step more was necessary: that which would allow each gun to command the whole sweep of the horizon, and to be available for duty upon either beam and any bearing: the adoption of the centre-line turret. But before tracing the evolution of the turret, let us recapitulate the typical ships built between 1860 and 1873 which composed our central-battery fleet.

The germ of the central-battery idea may be seen, perhaps, in the belted Minotaur, in which, in order to allow the chase guns to be fought from behind armour, a transverse armour bulkhead was worked, at a distance of some 25 feet aft of the bow. Had foreign influence not exerted itself it may be supposed with reason that from the Minotaur the central battery would have been evolved. However this may be, the evolution was hastened by French initiative; for in each of the two wooden ships Magenta and Solferino, laid down in ’59, was found a complete two-decked central battery whose whole depth was faced with armour for the protection of fifty-two 5-ton cannon, the rest of the ship’s water-line being protected by an armour belt much narrower than that of the Gloire. In imitation of this plan our own designs were prepared; and gradually, and only by a series of steps, we achieved what our rivals had obtained in a single stride.