Page:The New International Encyclopædia 1st ed. v. 05.djvu/109

COAST ARTILLERY. 81 COAST DEFENSE. used in the United States will be found in a publication of the War Department, Modern Guns and iVortars (Washington, 1895), which was prepared for the instruction of artillery gunners. Consult, also, BrulV, Ordnance and Gunnery (New York, 1900), and Drill Reguhi- tions for Coast Artillery United States Army, which are publislied from time to time by the War Department. The construction of coast artillery and other cannon, together with their carriages or mounts, is described and illustrated under Ordnance, which should be read in connection with this article, while the historical development of coast artillery as well as uf cannon of all forms is discussed under Artillery. The use of coast artillery as a means of defense is treated tinder the title Co..ST Defen.se, where the tactics of coast artillery are described. The forts and other defenses in which coast guns are mounted are discussed in the article Fortification. COAST DEFENSE. The defense of a sea- coast involves the principles of l)oth strategy and tactics. In considering the principles of strategy applicable to coast fortification it is essential to take into account the navy as our first line of de- fense. Every nation possessing a coast line has commercial interests, to protect which she re- quires a navy. Her fleet, whatever its strength, will recjuire points of support on the home coast, to serve as a basis of operation in attack or defense. These points of support contain all the material necessary for building or equipping ships; they furnisli all the needed men and sup- plies to the navy, and must offer for a beaten fleet, or one which on the outbreak of war lias not yet completed its equipment, a safe harbor to repair damages or complete equipment. The material of a navy is very expensive and is diffi- cult or impossible to secure after war has begun; consequently, the greater ])art must be prepared in time of peace and collected at the points of support, for which purpose extensive depots, magazines, and other constructions must be erect- ed. To prevent all these constructions from be- ing demolislied at one blow, and to guard the fleet, while still taking in supplies or completing its equipment, against surprise, these points of support must be protected by suitable means, and this is the purpose of fortifications. The only points of a coast that fulfill the con- ditions imposed by these considerations are the larger harbors (always bays and mouths of rivers), and they must be fortified not only against attack by sea, but also again.st land at- tack, for the late war between Japan and China showed conclusively that important naval ports ( Port .rthur and Wei-hai-wei. for example ) may be taken by forces landed on the coast without risking an attack on them by sea. In applying the principles of land tactics to the selection of sites for. and tlic construction of. sea- coa.st forts, some modifications must be introduced, due to the fact that the enemy in the latter case is confined to the navigable channels, so that all his possible flanking attempts can be foreseen and provided against. The principles of tactics which find application here are: (1) To obstruct the enemy's advance, while leaving free that of f lie forces of the defense for offensive movements : in other words, so to obstruct the water ap- proaches against the enemy as to leave free en- trance and exit for the defending fleet. (2) To be superior to the enemy at the point of attack; that is, to bring to bear on the channels of ap- proach a lieavier fire of higli-power guns and how- itzers and mortars than any fleet able to operate there can bring to bear on the defenses. (3) To place the isolated units for most etl'ectivc action so as to be mutually supporting; this is accom- plislied by scattering the torts to prevent the en- emy from concentrating his fire, at the same time arranging them so that fire can be concentrated on him. (4) To protect well the llanKs of the posi- tion and compel the enemy, if he attacks at all, to make a direct frontal attack. This is done by closing all unnecessary channels, by protecting the obstructions by means of rapid-tiring guns and the operators by means of boinbproofs, and at night by illuminating the obstructed field with search-lights. (5) To provide means for oft'ensive returns against countermining operations, either by means of a sw-arni of torpedo-boats, or by bat- teries for operating movable torpedoes from the shore. There are two systems of guns in use in coast artillery: the flat trajectory, high-power guns, ilesigned to pierce the side armor of battle-shi])s, and the high angle pieces (howitzers or mortars) whose projectiles are designed to fall on the ilecKs. Both are necessary, and each has its proper sphere of action, the former having by far the greater accuracy, and the latter attacking the battle-ship at its weakest point. In Europe how- itzers are generallj- preferred ; but the recent tests of mortars near Portland, Maine, have proved the greater value of the latter. The calibre of the fort guns must be at least equal to that which the depth of water in the channel will enable the enemy to bring against the defenses and suflicient to pierce his armor at the outer mine field, or at about two-mile range. The greatest thickness of Kruppized steel used in the latest battle-ships is about 12 inches at the belt, and to penetrate this at the required range will require a 10-ineh gun. The average thickness of deck armor most in use at present is about 3 inches of hardened nickel steel, and to penetrate this a high-angle gun (howitzer or mortar) 12 inches in calibre will be required. These, then, are the ma.ximum calibres required against battle-ships, but to prevent dis- tant bombardment of cities, etc., there is a 12-ineh rifle and for close ranges also an 8-inch rifle. Armored cruisers have from .5 to 6 inches of hard- ened nickel-steel armor, and to penetrate their armor within the mine field (where they first come seriously into play) will require a 5-inch or C-incli rapid-fire gun. The smaller vessels have but little armor protection, but as they come into action at the outer mine field (about 3330 yards) the smaller calibre guns to fight them must have the necessary penetration at that range, conse- quently must be about 2.5 to 3 inches in calibre. The number of guns of each calibre should be at least half of, and preferably equal to. those the enemy can bring to bear. The latter is deter- mined by noting on the map the length of channel (within three miles of the fort considered) which the enemy's fleet can occujiy, and allowing from five to ten ships to the mile. From the depth of channel the ships of the enemy which can go there can be determined, and from their armor and armament the kind and number of guns required. If the enemy's armament is not known, then in deep channels from 30 to GO guns of fi inch calibre .^nd over must be allowed to the mile (Abbot).