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Defence against Tanks. In describing the defence of an entrenched position, no mention has so far been made of tanks, although the use of these is now one of the most important fea- tures of the attack. And this is because the best method of deal- ing with attacking tanks is still a matter of speculation.

Tanks advancing against a position are screened from the aimed fire of distant artillery by the barrage which precedes them. If ordinary field guns are concealed in the front line to destroy them, these are generally destroyed themselves by the bombardment. Some tanks may be hit by the defender's barrage, but this is likely to be either thin or partial. At a later stage some of the tanks will be hit by those field guns which remain behind till the attacking infantry are within 500 yd. of them. The uncertainty of defence by mines and by ditches has been shown by experience. Tank-stopping rifles and tank- stopping machine-guns are effective against the present tanks, but those used in the next war will be proof against anything short of a gun.

It is often assumed that attacking tanks will be engaged by the tanks of the defence. But when a position is subjected to a fully organized attack the latter will not find it easy to do this. If kept well up to the front in readiness they will be destroyed by the bombardment, to which they offer large targets. If kept some 3 m. in rear till the attacking tanks appear, they will, even if their movements be correctly timed, have to pass through the attacker's bombardment and barrage, and possibly through their own barrage. Moreover, the tanks of the defence are presumably fewer in number than those assembled for the attack, so that even if they arrive in time they will be out- matched.

The best solution of the difficulty would appear to be the provision of special anti-tank guns, large enough to put an armour-piercing shell into a tank, and small enough to be pro- vided with strong cover. A light mountain gun, capable of being divided into man-loads, would be suitable for the purpose. These guns might be in dugouts some 400 yd. behind the front line, where they would not be subjected to the full violence of the bombardment. When this was lifted from the front line preparatory to the assault, the anti-tank guns would be put together and run up on to platforms level with the tops of the trench parapets, giving them sufficient command to see the attacking tanks as they charged the front line.

A regular defence in depth by anti-tank guns would have to be provided for, additional anti-tank guns being sited behind each successive line of defence, as well as in " strong points."

These anti-tank guns would have to be " silent " guns, at least so far as their own firing emplacements were concerned. Their provision, on a scale sufficient to stop a tank attack, would involve a considerable addition to the artillery of the defence. For even if the infantry guns of acconjpaniment were utilized as anti-tank guns, there would not be enough of them. Infantry guns are required at the rate of one per 100 yd. of the front of the attack, or at most 16 to a division; while if a division holds 3,000 yd. of entrenched front it will require three lines of anti-tank guns sited 200 yd. apart, that is 15 in each line, or 45, besides some 15 for " strong points." This calculation shows that 60 anti-tank guns per divisional front are required, or about one per 45-50 yards.

It may be suggested that the anti-tank guns of the first line could withdraw to the second line, and then again to the third line. But since they have to remain in position till the attack- ing infantry have almost reached them, in order to deal with the tanks, there would appear to be little chance of withdrawing the guns, although the detachments may be able to escape.

The expenditure of men and material for a special purpose which the above scheme involves is not to be undertaken lightly. But it has become manifest that attacking tanks are safe from distant artillery, and must be engaged by guns on the spot. Therefore these guns will have to be provided; and, so far as our present experience extends, the provision of numerous small guns in the trench area seems to be the best answer to the menace of the tank attack.

IV. THE PHASE OF EXPLOITATION

In France, in the latter half of 1918, after four years of trench fighting, the retreat of the invader brought the combatants into the open once more, but under changed conditions. The artillery had increased in numbers relatively to the infantry; their ammunition supply admitted of a greatly increased volume of fire, and their range had been extended. Mechanical traction, even for field artillery, had to a great extent come into use, especially in the French army, and medium, heavy and even superheavy ordnance were able to accompany the troops in the field.

Under such conditions the troops had to adapt themselves to a new method of warfare. The pre-war battery commanders, experts in mobile warfare, had been replaced by others whose training had begun in the trenches. Few of the officers and men had any knowledge of mobile warfare as thought and practised before the war, and even these found that they had to learn their work afresh.

Moreover, owing to the strain upon the munition factories manufacture had come to be limited to projectiles of simple design suited for mass production, and shrapnel had disappeared from all but the field-gun equipments. In the French army, even these had only 5% of shrapnel, the rest being H. E. shell.

The mobile phase did not last long enough for the employ- ment of artillery in a war of masses to be thoroughly studied. The conclusions arrived at cannot be regarded as final, and are subject to possible modifications due to the more extensive use of tanks, motor artillery, and motor infantry.

Horse Artillery. The old methods of manoeuvre are not applicable to a war in which the line of battle is continuous, with no flanks. Whatever the general procedure selected by the attacker, or pursuer, he will keep close touch with the defender's line, and maintain pressure on it at all points so as to deny him freedom of manoeuvre. The object of the pursued is to break away from the pursuer, and to lose touch with his troops, so as to regain freedom of manoeuvre in order to counter-attack, to take up a defensive position, or both. In this nature of war- fare horse artillery are of great value. (In the coming age of motor artillery, the term " horse artillery " must be understood to mean a more mobile arm than the divisional field artillery, capable of working with the " cavalry " of the future, however that arm may be transported.) The lessons of the first phase of the western campaigns and of the Palestine campaign of 1918 still hold good.

The Attack. The result of the continuous line of battle is that all attacks are, tactically, frontal attacks. Within the limits of an army corps or divisional frontal attack there will be local flank attacks; thus it is often easier to envelop a strongly held locality than to take it by direct assault. But these are minor operations which concern the trench mortars, the guns of accompaniment, and the gun-carrying tanks rather than the main body of the artillery.

Intimate cooperation of gun and rifle is more necessary than ever, owing to the increased fire-power of the defence afforded by the machine-gun. The breakdown of liaison par le has in the opening phase of the war has already been referred to; in the concluding phase this was still more marked, and the French especially complained that their artillery misused the increased range of their field gun by keeping far in rear of the infantry, where communication with them was impossible, instead of pressing forward to find out what was going on. But even if liaison is so far effective that the artillery know when the infantry is checked by fire, it does not follow that they will be able to discover the source of the fire. Possibly the infantry may not know themselves. Aeroplanes may be of great help both in locating it and in promptly conveying the information to the supporting artillery. It is even conceivable that battery com- manders will direct the fire of their guns from aeroplanes. But the possibilities of " liaison by the air " are still too vague to count upon.

The Barrage. Since, under present conditions, the artillery cannot always give the infantry direct support by killing the