NAVAL ORDNANCE Naval Ordnance' is distinguished from Field Ordnance by the circumstance that the guns are carried on a rapidly moving plat form subject to the uncertain oscillations of a ship at sea, and are required to hit a rapidly moving object. This entails special mountings, with very sensitive training, elevating, and sighting gear, suitable for counteracting such motion, and special firing arrangements and means of controlling the fire from favourable positions in the ship. The military artillerist is confronted with a task comparable to that of discharging a projectile from a gun in the Tower of London and placing it in the centre court at Wimbledon. The task of the naval artillerist, however, may be compared to firing from a rapidly moving train to hit another train, many miles away, moving at an unknown speed in an unknown direction. The anti-aircraft gunner has to deal with a rather similar problem, but the difficulties of the naval artillerist are considerably increased by the ship's motion, especially in a heavy sea.
'The subject is restricted to naval weapons and their mountings for the discharge of projectiles by propellants, and does not include de structive engines which contain their own propelling machinery, such as torpedoes and rockets.
Though the World War developed certain special weapons peculiar to each Service and associated with such special condi tions as trench and anti-submarine warfare, the general character of naval service guns is similar to that of land service, the con struction of which has been outlined. It is not the gun, but the means of working it, that differs considerably, hence the difference in the design of the mounting and in the fire control system is very marked. The mounting design is further affected by the cen tralized position of the ammunition supply and the availability of power in a ship—conditions which do not prevail in the field.
The development of naval guns has naturally been in the direction of increase in muzzle velocity and in size, giving greater accuracy, longer range, and greater striking energy. The progress during this century is indicated below : This increase in power and working pressure means a cor responding increase in the strength of the gun which has been obtained by progressive improvements in the quality of steel and the technique of construction. The power of the gun is decided by the primary purpose for which it is required such as penetra tion of armour at long range or repelling attacks by destroyers and aircraft. For the penetration of armour the higher the power the better, on the principle that success comes to the ship that can hit hardest and most often at the longest range. For defence from aircraft and both attack and defence in the case of destroy ers, rapidity of fire is of greater importance than power.
In the nature of things, the size of the gun is related to the size of the ship, but the World War produced notable exceptions such as submarines armed with 12 in. and monitors with 18 in. guns. Attempts have been made by certain naval powers to reach agreement limiting the size of guns for certain classes of ships. As the result of the Washington conference (q.v.) in 1922 it was agreed between the signatories to restrict battleships to 16 in. and cruisers to 8 in. guns. At Geneva in 1927 agreement was reached between Britain, U.S.A. and Japan, to limit destroyers and submarines to 5 in. guns, but failure to solve the cruiser problem left this matter adjourned sine die.