Within the investing lines of the Western Front the German Armies were besieged, the barrier reaching from the Belgian coast to the frontier of Switzerland, while the armies of Austria-Hungary were similarly penned in by the army of Italy, from Switzerland to the Adriatic. The internal collapse of Russia, in 1917, enabled von Hindenburg to assume the offensive, with upwards of 1,500,000 men released from the Eastern Front, and part of this reserve power was projected, with the Austro-Hungarian Armies, in a fierce attack on the Italian lines. The success of this manoeuvre continued until reinforcements were dispatched from other parts of the Allied lines, and a diversion in the region of Cambrai by the British III. Army, under Sir Julian Byng (November 20, 1917), prevented the dispatch of further German reserve power to the Italian Front, and necessitated a counter-thrust in France. The battlefields of France again resumed their importance as the vital point in the theatre of operations, and in the spring of 1918, profiting by the improved positions and prospects in the West, Ludendorff attempted to break through the investing lines on a 50-mile front. The attack was heralded by a terrific bombardment, and culminated in a desperate thrust against the British Armies north and south of the River Somme, the points of penetration aimed at being the British right, where it was linked up with the French on the River Oise, in the neighbourhood of La Fère, and the British line of communications in the neighbourhood of Amiens. The whole British line opposite the thrust was hurled back and the territory regained by the Franco-British {53} advance on the Somme in July, 1916, was recaptured by the German Armies. But this was not a battle for towns or territory, as the German hammer blows were intended to drive a wedge between the British and French Armies, to roll up the British flank northwards to the sea-coast and the French flank southwards to Paris, and to capture the main line of communication between these Northern and Southern Armies. By skilful reinforcement of threatened points, Marshal Haig frustrated the primary object of the attack, and by the aid of the French Armies the whole line fell back, disputing the ground with the utmost resolution, and maintaining the line without losing touch between the south and north. The German wedge was thrust in, but every attempt to effect a breach and to pour through the line was frustrated by the Allies. During the battle the French and British Armies became intermingled, and to preserve unity of control a Generalissimo was appointed in the person of General Foch, who had commanded the French IX. Army at the First Battle of the Marne in September, 1914, and the French Armies of the Somme during the advance in July, 1916. General Pershing, commanding the Army of the United States, gave a free hand to the Generalissimo to incorporate American troops wherever they might be needed in the field, and Marshal Haig and General Retain remained in command of the British and French Armies.
METHODS OF ATTACK.—The object of every attack is to break down the enemy's resistance by the weight and direction of fire and to complete his overthrow by assault, by the delivery of a decisive blow with as large a portion as possible of the attacking force against a selected point or portion of the enemy's position. The term "Decisive Attack" does not imply that the influence of other attacks is indecisive, but rather that it is the culmination of gradually increasing pressure relentlessly applied to the enemy from the moment when contact with him is first obtained.
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TWO PLANS OF ATTACK.—There are two plans of attack. In the first, the direction in which the decisive blow is to be delivered is determined beforehand; an adequate force is detailed and pushed forward for this purpose, and at the same time another part of the force is detailed to attack another portion of the enemy's position, to keep his attention there, to pin his troops in position, to prevent him sending reinforcements to the part mainly threatened, and ultimately to drive home with the successful assault of the main attack. The rest of the force is small and is retained in General Reserve to meet emergencies.
In the second plan, a general action is developed by a part of the attacking force and the remainder is retained in General Reserve, to be thrown in when the opportunity arrives, at the right time and in the right place. In this case, the "remainder" is not less than half the available force.
The first plan can be adopted when the commander of the attacking force has definite information as to the extent of the enemy's position, when he knows where its flanks rest and when he knows the approximate strength of the forces arrayed against him. It must also be possible, without undue risk, to divide the attacking force into parties of such strength that neither can be overwhelmed by the enemy in detail, and it is to be noted that in the case of a serious check there is only a small General Reserve to restore the battle. The second plan can be adopted when information is incomplete, and owing to the strong force retained by the commander in General Reserve, the situation can be exploited and developed by fighting without undue risk.
STRENGTH OF THE ATTACK.—It must always be remembered that a commander can never be too strong when making an attack, for he can never be perfectly sure of what force he may encounter, or at what moment the adversary may make a counter-attack. An attack {55} on an enemy presupposes a superiority of force at the place where the attack is made, for war is but the art of being stronger than the enemy at the right place at the right time, and for an attack to have a reasonable hope of success the attackers, at the point where the penetration takes place, must be superior.
DISPOSITION OF THE TROOPS.—Each phase of the Attack will normally require three separate bodies of troops for its execution: a Forward Body to seek out for, and when located attack, the enemy along the whole front of the sector allotted to it and by relentless pressure to wear down the enemy's resistance in order to discover the weak portions of the defence; Supports to penetrate the weak portions of the defence and forthwith to attack the flanks and rear of those portions of the defence which are holding up the Attack; with Local Reserves for dealing with local counter-attacks; and a General Reserve by means of which the commander exploits success or retrieves failure.
THE FORWARD BODY, THE SUPPORTS, AND THE LOCAL RESERVES.—The paramount duty of all leaders in the firing line is to get their troops forward, and if every leader is imbued with the determination to close with the enemy, he will be unconsciously assisting his neighbour also, for, as a rule, the best method of supporting a neighbouring unit is to advance. But an attack is often held up by well-directed machine-gun fire, and by determined and well-trained riflemen in concealed or well-prepared positions. The tactics to be pursued under these circumstances are thus outlined in "Infantry Training, 1921": "When forward troops are held up by the enemy's organised fire at close ranges they must keep him pinned to his ground and absorb his attention by maintaining a vigorous fire and working their way closer when opportunity offers. It will be the duty of the Supports to turn the flank of, and enfilade, that portion of the enemy's defences where a garrison is opposing {56} the Forward Body. To achieve this, Supports may have to quit their direct line of advance and follow in the wake of a neighbouring unit, which is able to advance. It must constantly be borne in mind that pressure should be brought on the enemy by supporting troops in places where the attack is progressing rather than where it is held up, never by the mere reinforcement or thickening up of a line of troops who have been unable to advance. There must be no slackening of pressure, meanwhile, by the forward troops who are temporarily held up, or the defenders will be able to turn their attention to the flanking attacks which are being directed against them." The Local Reserves are for local counter-attacks by fire or movement against similar efforts by the Local Reserves of the enemy. In modern campaigns this work is effectively carried out by the overhead fire of machine guns distributed in depth, and the mobile Local Reserves may thus consist of smaller units detached for the purpose by the Forward Body or by the Supports. During the great German offensive in the spring of 1918 the Attacks on the Somme and the Lys were constantly held up by the vigour and tenacity of the Franco-British defence, and to meet the necessities of the case the following instructions were issued by the German General Staff: "If the assaulting troops are held up by machine-gun fire they are to lie down and keep up a steady rifle fire, while Supports in the rear and on the flank try to work round the flanks and rear of the machine-gun nests which are holding up the Attack. Meanwhile, the commander of the battalion which is responsible for the Attack is to arrange for artillery and light trench-mortar support, and should protect his own flanks from machine-gun fire by means of smoke."
THE GENERAL RESERVE.—In a modern campaign against civilised troops it will seldom, or never, happen that the efforts of the Forward Body, Supports, and Local Reserves will annihilate the enemy and so prevent him from regaining cohesion and fighting power. Even if {57} every part of the position against which an assault is delivered is captured and held, the enemy will not, by that means alone, cease to exist as a fighting force, and if he is permitted to withdraw with a semblance of order and moral the work of the Attacking Force will be of little avail. The destruction of the enemy and not the mere capture of the ground of the encounter is the ultimate aim of the commander. He will, therefore, accept the best available opportunity for the destruction of the enemy by overwhelming them in some part of the battlefield during the successful operations of his Attacking Force. It may, however, happen that the efforts of the Attacking Force are generally unsuccessful and the enemy may be on the point of gaining the upper hand. By means of the General Reserve the commander exploits the success or retrieves the failure of the Attacking Force. The commander will have selected some point or position in the enemy's defensive system against which he can direct his decisive attack. This point cannot, as a rule, be determined until it has been revealed by the successes of the Forward Body and the Supports, and when it has been selected it must be struck unexpectedly and in the greatest possible strength. While, therefore, the Forward Body, Supports, and Local Reserves must be adequate in numbers for the task allotted to them, a commander will generally retain about half his available force for the delivery of the Decisive Attack, and when this decisive blow has been delivered the Reserve will carry on the pursuit of the beaten enemy until such time as other Infantry, or Cavalry, or Tanks, have caught up and passed them. If the attacking troops fail to obtain their objective the commander has at his disposal the means of relieving exhausted troops and of dealing with the "decisive counter-attack" of the enemy.