TYPES OF ARTILLERY The function of land artillery is to kill troops at a range beyond that of a hand weapon, and to destroy material, obstacles and defences. Various natures of artillery have been developed, suit able to the tasks to be fulfilled. The four main classes are : field artillery (of which mountain, infantry-accompanying and horse-artillery are lighter varieties) ; heavy artillery (which is subdivided according to power of foe and of movement) ; anti aircraft artillery; trench artillery or mortars.
Thus British artillery is classified, in detail, as follows :— _ Light (in India, Mountain) artillery (2.75-in. guns and 3.7-in. howitzers).
Horse artillery (13-pdr. guns).
Field artillery (18-pdr. guns and 4.5-in. howitzers) .
Medium artillery (6o-pdr. guns and 6-in. howitzers).
Heavy artillery (6-in. guns, 8-in. and 9.2-in. howitzers). Super-heavy artillery (guns of 9.2 in. and upwards, and howit zers of i 2in. and upwards).
Anti-aircraft artillery (3-in. guns).
This is capable of accompanying the ad vanced fighting line of an army. It consists of light guns and howitzers able to keep pace both on the road and across country with the arm it is supporting, and to come into action without previous preparation of the ground. The field gun is, in all armies a piece throwing a shell of from 15 to 18 lb. to a distance of at least Io,000yd., although effective ranges are generally less, and weighing less than 3ocwt. in action. Before the introduction of mechanical traction the weight was limited to 24cwt. and the range to 6,000yd. The present limit of approximately 3ocwt. is due principally to the fact that this weight is as much as a gun-detach ment of six men can man-handle. All modern field guns are quick firing; that is, the gun recoils on the carriage and returns to the firing position, while the carriage remains steady. This saves the delay due to running up and relaying the gun after each shot, and increases the rate of fire from two rounds a minute to 25. It also enables the gun-detachment to remain behind the gun-shield, in stead of having to stand clear of it during the recoil of the carriage.
The field howitzer differs from the field gun in that it throws its shell high into the air, so as to descend at an angle in excess of
This enables it to reach targets, such as men in deep trenches, protected from the direct fire of guns. As this high-angle fire requires less effort than direct fire, the field howitzer is able to fire a shell double the weight of that of the field gun, without exceeding the same weight of equipment. Howitzer fire, from its nature, is local in effect, and at targets of considerable depth from front to rear, such as advancing infantry, it is inferior to the flat-trajectory fire of guns. In most armies one-fourth of the field artillery consists of howitzers, and three-fourths of guns.
Special natures of field artillery are :—(a) Horse artillery, which can keep pace with cavalry across country. For simplicity of ammunition supply, the gun may be the same as that of the ordinary field artillery, but in any case the weight behind the team is reduced by mounting the gunners on horses, instead of carrying them on the limbers and ammunition wagons (caissons in American usage). (b) Light or Mountain artillery, which is divided into separate loads which can be carried on pack animals or transported for short distances by hand. It is used in country impassable to wheeled carriages, and has been adapted to serve the newly found need for artillery of accompaniment (i.e., the close support of infantry) . The provision of a special light gun or howitzer to accompany the infantry has been a subject of con troversy and research since the World War, but it cannot be said that any country has yet found the ideal weapon.
This consists of guns and howitzers of greater range and shell-power than field artillery, yet sufficiently mobile to accompany the infantry advance. The usual types are a gun of approximately sin. firing a shell of about 6o lb. to a range of i6,000yd. and a howitzer of about 6-in. firing a shell of about
lb. to a range of 12,000yd. The 6o-pdr. gun is designed to fire upon distant road crossings, railway junctions and other im portant points which have to be engaged without delay, and before the heavy artillery can come up. The 6-in. howitzer fires a power ful shell capable of demolishing buildings and of destroying entrenchments other than those of a semi-permanent nature. It is the principal weapon used in trench warfare. Both pieces are available for counter-battery work, that is, for attacking en trenched guns which have been located by aircraft or by sound ranging. The medium gun is an enlarged edition of the field gun. The 6-in. howitzer was formerly a short, handy piece, but owing to the increased range now required of it the length of the modern type is as much as 25 calibres.
This term is applied to pieces heavier than medium artillery including guns up to 8-in. calibre and howitzers up to 9.2-in. calibre. In modern war it is necessary to attack objectives at least Iom. behind the fighting front and accordingly road-mobile heavy artillery, which can engage targets beyond the range of medium artillery, has been introduced. The principal gun of this type is the 6in. gun, the latest pattern of which ranges 15m. with 100 lb. shell. It can be fired from the ground without the delay entailed by building a platform ; wire mats or similar appliances are used to prevent the wheels from sinking. Modern 6-in. guns have split-trail carriages to enable them to be traversed quickly.
A howitzer heavier than the 6-in. is required for destroying bridges and semi-permanent entrenchments. The 8-in. howitzer fires a 200-lb. shell and ranges 18,000yd. ; the British 9.2-in. howitzer, known in the war as "Mother," fires a 290-lb. shell ranging 12,7ooyd.; and the new American 24o-mm. (9.45-in.) how itzer, a type of gun used also by the French, fires a 356-lb. shell to a range of 2 5,000yd. This piece is accepted as the typical mod ern heavy howitzer, and is about the largest piece likely to be transported by road in future warfare, as it is considered that heavier natures are better transported by rail.
As the size of a shell is increased, the effect increases in a higher ratio. Much of the destructive effect of a i,000-lb. shell is due to the blast, not to the local destruction caused by the high-explosive charge. The effect of the blast is to bring down walls as much as 5oyd. from the point of burst, to cause roofs to fall in, and generally to wreck a great building such as a railway station or factory. A single hit from a i 2-in. shell might destroy a bridge altogether, whereas ten hits from 6-in. shells, equal to the same weight of ammunition, would only cause easily reparable damage. A further advantage gained by the use of very heavy guns is the greatly increased range. Thus the British 9.2-in. gun throws a 38o-lb. shell 14m. while the new U.S. i4-in. gun ranges 22m. with 1,56o-lb. armour-piercing shell, and nearly 3om. with a somewhat lighter stream-lined shell. These considerations have led to the extensive employment of super-heavy pieces in land warfare.
Formerly a howitzer was a low velocity weapon fired at a high angle of elevation, while a gun was a high velocity piece with a flat trajectory. The howitzer conveyed the shell to the target with a much smaller propelling charge than the gun, and consequently lasted much longer than the gun before it was worn out. At present all guns are mounted so as to fire at high angles of elevation, in order to attain their extreme range, and use reduced charges as well as full charges and super charges in order to save wear. On the other hand, the range re quired of howitzers is now greatly increased so that the 1914 pattern, 12 calibres long, has been superseded by howitzers of 25 calibres and over, firing much heavier charges. The distinction between gun and howitzer is therefore tending to disappear.
Super-heavy pieces are usually fired from railway mountings or at least are transported by rail. But an invader may find it necessary to bring up large howitzers, for the reduction of for tresses near the frontier, before the captured railways can be made available. The difficulty in the way of transporting these pieces by road is the limit of the weight which bridges can carry. Even on the great main roads of western Europe this weight is not more than 3o tons, and on country roads it may be as little as 5 tons. This implies a special type of howitzer, comparatively short and light, capable of throwing a heavy shell to a short range. The German 42-cm. (i6.5-in.) howitzer brought up for the siege of Antwerp was only i 2 calibres long, and weighed 212 tons, or about 29 tons on its special wagon. It threw shell of i 5.7cwt. to a range of 10,3ooyd. It was drawn by three traction engines with a fourth in reserve for hills. The recoil gear, carriage, platform (in two parts) and gear for mounting the howitzer formed sepa rate loads, and the piece required 13 traction engines altogether.
The French have a 3 7o-mm. (14.6-in.) howitzer, only 8 calibres long, throwing an 8cwt. shell i 1,5ooyd. It is rendered road-mobile by being carried on two road trucks, one following the other, with an arched girder between them from which the piece is suspended. The United States has an experimental 9.45-in. howitzer on a cater pillar mounting, driven by electricity from a separate vehicle which carries the i5oh.p. power unit. The total weight of the vehicle carrying the howitzer is 13 tons.
During the World War the Germans bombarded Paris from a distance of 76m. with specially built long-range guns, throwing 265-lb. shells. This long range was obtained by using a velocity of 5,0oof t.sec., and firing at an eleva tion of 55 degrees, so that the shell passed through the layer of dense air nearest to the earth, and reached the comparatively thin air at a height of iom. which opposed little resistance to its flight. In this case the greatest height of the trajectory was 24m. Guns of this type cannot fire more than about 3o rounds before they are worn out. Owing to uncertain weather conditions, the accuracy is poor; while the gun is new the shells may be expected to fall within a space of 2m. long by 4m. wide, but as the gun becomes worn these limits are soon exceeded. Aeroplanes are far more efficient than guns for this kind of bombardment, as an aeroplane can now carry a 2,000-lb. bomb and can drop it with far greater accuracy, at such distances, than the gun.
The problem of hitting a target moving in three dimensions is a difficult one and the additional complication due to a curved trajectory has to be eliminated as far as possible. All A.A. guns are therefore flat-trajectory weapons with high muzzle velocities. Ordinary field guns mounted on lor ries or trucks, as employed in the World War, are of little use. Mobile A.A. guns used in the fighting line, are usually on low wheeled platforms which can be drawn behind a lorry. On com ing into action, the platform is lowered to the ground, and levelled by screw-jacks at each corner, so as to bring the pivot exactly vertical. Semi-mobile guns, used in sedentary warfare, are on heavier platforms which are carried in sections and put together before firing; and non-mobile guns, for the defence of fortresses and cities, are on solid concrete or caisson platforms.
The ammunition used with A.A. guns is shrapnel or high explosive shell; a proportion of the shells are fitted with tracers. A tracer is a small firework in the base of the shell, which leaves a trail of smoke to mark its flight. This is necessary, since an ordinary shell fired into the air disappears until it bursts, and there is nothing to show whether it has passed close to the target or otherwise. The shell is fused so as to avoid endangering one's own troops by the shell falling among them.
Fire at aeroplanes is entirely by prediction ; the course and speed of the target are measured by optical instruments, and the gun is fired at the point where the aeroplane is expected to be, making due allowance for the time of flight of the shell. If the first shot or salvo misses, the plane will at once begin to dodge, and it is useless to fire at it until it has again settled down to a regular course.
When two opposing forces are entrenched, they tend to press forward till their advanced works are within i ooyd. or less of each other. The same thing occurs in siege war fare, when the besieger extends his front trench till it is close to the fortress. The need then arises for a weapon capable of throw ing a heavy bomb to a short distance, yet which is so small and light that it can be carried through the trenches. The original piece of this type is the Coehorn mortar used in the sieges of the i8th century. The modern type was introduced by the Germans at the beginning of the World War. The Krupp Minenwerfer was a light gun of 2-in. calibre mounted on a short plank. The 50-lb. spherical bomb rested on the muzzle, and had a tubular steel "stick" which extended down the bore of the gun. The piece was fired at an angle of 45 to 75 degrees of elevation, and its extreme range was about 450yd. The so-lb. bomb, with its high-explosive charge, was capable of wrecking a "dug-out" or blowing in the walls of a trench so as to block it.
As the weight of the 50-lb. bomb rendered ammunition supply in the front trenches a laborious proceeding, the British introduced the light Stokes trench mortar, firing a io-lb. bomb. This is a weapon of a different type. It is a light steel tube of 3-in. calibre, with a spike projecting into the breech end of the bore. The cylin drical bomb has a small cartridge and percussion cap fixed to its base; it is dropped into the muzzle and slides down till the percus sion cap strikes the spike, when the cartridge is ignited and the bomb blown out. The extreme range is about 1,2ooyd. This en ables it to be used from a point well back in the trench system where it is safer and less likely to draw fire than in the advanced works. A 25-lb. Stokes mortar was afterwards introduced, and was used principally for firing smoke shell. Later on, the bombs were fitted with air-vanes to increase their accuracy. The 3-in. Stokes proved such a handy weapon that it was used in mobile warfare as an infantry gun, for the reduction of "strong points" encountered in the infantry advance. Being a high-angle weapon, it was useless against moving tanks.
Owing to the difficulty of supply ing heavy ordnance in sufficient quantities trench mortars were introduced in 1915, capable of throwing a zoo-lb. shell about 1,200 yards. The principal piece of this type was the Gatignolles 240 mm. (9.45-in.) mortar. This was in two pieces screwed together, and was fired from a mounting fixed on a bed of wooden balks. The total weight was about a ton, and it was divisible into five barrow loads. The Allies used this weapon for firing from posi tions towards the rear of the trench system, where it could be turned on the front trenches in case the enemy invaded them. The Germans used, for the same purpose, a rifled 170-mm. (6.69 in.) trench mortar, firing a shell of i io lb. to a range of 1,25o yards.
