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Rh The weight of artillery opinion is against the automobile gun- carriage, which is too large to dig in or conceal, and too vulnerable; moreover, the motor is useless when the gun is in action, and might better be employed elsewhere. Pulling a gun behind a tractor has many advantages, and is economical of transport, since the tractor carries the men and first supply of ammunition. The difficulty is that an ordinary Q.F. gun-carriage breaks up when drawn by a tractor at any pace faster than a walk. In March 1918, at the time of the German attack, the French brought up a large number of field guns drawn by lorries. These guns had to be fitted with rubber-tired wheels for the purpose. Again, in the autumn of 1918, the French (who were by then very short of horses) used field guns carried on lorries, with the gun-teams carried in motor-omnibuses converted into horse-floats. Only sufficient horses to bring the guns into action were transported in this way. By the end of the war the French had 266 tractor-drawn batteries of divisional artillery, and 306 batteries on lorries.

The French sometimes adopted a still bolder solution of the prob- lem, namely, carrying the 7-ton caterpillar tractor on a special road lorry. Some authorities are disposed to think that this heroic method offers a better prospect of success than trying to produce a tractor that shall be able to cross country and also to travel fast on the road without damage to the surface. For a light caterpillar tractor, capable of pulling a field gun across country, may be made to weigh 50 cwt. or less, so that a large 4-ton lorry can carry both the tractor and a 3O-cwt. field gun as far as the point where the gun has to leave the road. However, the method of carrying one motor on another seems so wasteful that it is regarded as a last resource.

The Italians have tried carrying the guns on lorries, with ramps to run them on and off, but find the system wasteful of transport ; the gun takes up so much space on the lorry that there is no room to load it to its full capacity with men and ammunition. In 1921 they were experimenting with low-travelling platforms, of which one or possibly two are to be drawn by elastic couplings behind a fast road tractor; the platform, which carries a wheeled field gun, is on rubber-tired wheels and is supported on road springs so as to run smoothly at 12 m. an hour. These are for reserve " army " field artillery, and the guns are to be drawn into position by the horses, or cross-country tractors, of the divisional artillery which they reenforce.

There is one set of conditions under which the carrier has the ad- vantage of the tractor, and that is in getting guns forward over the " crater-field " when this is very boggy. In the zone of contact of two hostile forces, when these are entrenched, the ground is pock-marked with shell craters, and in wet weather it may become a swamp into which any wheeled vehicle sinks, even if it is attempted to drag it behind a caterpillar. There are certain conditions of ground over which a caterpillar can carry a gun, though it cannot drag it. These must, however, be considered exceptional, and too rare to justify the adoption of carriers in place of tractors. Moreover, the sinking of the gun may be obviated to a great extent by using " girdles," which are linked plates surrounding the wheels. Girdles are also used on wheeled tractors for crossing soft ground.

A very important factor in the question of the motor transport of artillery is the necessity of using the agricultural motors of the country in time of war. The French are now endeavouring to pro- duce an agricultural tractor, mobile on and off the road, which shall fulfil military requirements and shall also be used in very large numbers for agriculture. The introduction of a proportion of auto- mobile gun-carriages, though spoken of by the French press, is a question which is still unsettled. The French guns up to the 6 in., and howitzers up to the 9-45 in. inclusive will be road-mobile, being divided into tractor loads, where possible not exceeding 5 tons net. All heavier natures will be on railway mountings.

In Italy, the intention is to have all the divisional artillery (which is to consist of field guns and field howitzers only) drawn by small agricultural tractors, road speed 5 m. an hour. These are not to be caterpillars but four- wheel-drive motors, and it is considered that the pattern adopted (Pavesi of Milan) will be sufficiently mobile across country. Girdles are carried for use on soft ground. The army field artillery will be drawn by fast road tractors as mentioned above. The corps artillery, consisting of 4-in. guns and 6-in. howitzers, will be drawn by wheeled road tractors of 50 and 55 H.P. These are also used for the component parts of heavy artillery loads up to the 12-in. howitzer inclusive. These also carry girdles for soft ground.

The question of artillery transport is more urgent in Italy than elsewhere, since the country produces no artillery draught-horses. Italy is the only country which has actually begun the conversion of horsed to motor artillery ; the United States and France, though they used motor artillery during the war, are still only preparing to intro- duce it as part of their permanent organization. The Italian "aulo- portata" army regiment of 48 field guns referred to above is the only such unit in existence. The reason why wheeled tractors, not cater- pillars, have been preferred is that owing to the nature of the cul- tivation there is no prospect of cross-country agricultural tractors of the caterpillar type being used on any large scale.

The United States are trying both tractors and automobile gun- carriages ; apparently they do not favour platform carriers.

The order of conversion of the different horsed artillery forma- tions to motor transport will probably, in all countries, be on

the following lines: (i) All transport which keeps to the road, including ammunition columns; (2) all guns and howitzers heavier than the divisional artillery; (3) army field artillery; (4) all first-line ammunition wagons; (5) guns and fighting battery wagons of the divisional artillery. It is, however, an open question whether army field artillery should not be con- verted to motor transport first of all, on account of the high importance of having a reserve of field artillery, able to travel long distances at a fast pace, available on the outbreak of war.

It need hardly be said that in future the artillery motors of the fighting formations will belong to the artillery and be driven by artillery drivers, not by men borrowed from the general transport corps of the army.

Road-Mobile Super-Heavy Artillery. One of the first sur- prises of the war was the reduction of the strong fortresses in Belgium and northern France by the German super-heavy artillery. These fortresses were designed to resist 6-in. guns and 8-in. howitzers, and the Germans brought up 12-in. and even i6-5-in. (42 cm.) howitzers by road to attack them. The limita- tions of the transport of heavy loads by road vary in different countries. The British used 22-ton traction engines in the S. African War of 1899-1902, at the end of which they were sold out of the service as too heavy for English bridges. The bridges on the continental " national " roads are stronger than most English bridges, and, on some routes, are capable of taking a gross load of 30 tons on four wheels. The 42-cm. howitzer was divided into loads, the heaviest of which was about 29 tons gross. It was no doubt built with regard to the roads by which it would have to travel. A short (25-calibre) 9-2-in. gun or long 8-in. gun would make loads of the same weight. However, in France it has been decided, as mentioned above, not to transport super- heavy ordnance by road. These pieces are all to be on railway mountings. The reason for this is the greatly increased range which was demanded of howitzers during the war; thus the British 6-in. howitzer in use in 1914, which ranged 6,000 yd., was replaced by a howitzer of the same calibre ranging n,6oo yd., and a similar increase of range was required of all pieces which, before the war, were classed as siege artillery. It is there- fore considered that it will always be possible to find or to build a position for heavy guns and howitzers on railway mountings within range of a fort or of any target which they may have to engage.

Liaison. An early experience of the war was the breakdown of the method of cooperation of infantry and artillery which had been taught in peace time. The French were the great exponents of this method. It consisted of liaison par le haul, which means, for instance, that the divisional commander de- tails a groupe of three batteries to support the attack of a brigade of infantry; and liaison par le bas, which means that the in- fantry brigade and artillery group commanders, and even their subordinates, the battalion and the battery commanders, keep up constant communication during the fight. Under battle conditions, liaison par le bas broke down at once. The British did rather better than the French, because they had five officers per battery as against three, and because they were trained in the use of the concealed artillery position, which necessitates distant communications. During sedentary war- fare communication was perfect; every company in the front- line trench had a battery to support it, and the battery prided itself on putting over a storm of shrapnel within 10 seconds of receiving the call for assistance. But as soon as the troops left their trenches, in advance or retreat, direct communication between infantry and artillery units ceased altogether. Tele- phone lines were cut by the enemy's fire; visual signallers were shot down, or, even if they succeeded in finding cover, the smoke and dust soon interrupted their view. Orderlies rarely succeeded in getting through, and the few that escaped being killed or wounded arrived too late for their messages to be of any use. Many devices were tried by the armies engaged; the German system of light signals was the least unsatisfactory. But the direct and intimate cooperation of infantry and artillery units was never realized.