Before an Advanced Guard commander moves off in compliance with his instructions he will take certain steps in accordance with these tactical principles. He will divide his troops into two portions, known as the _Vanguard_ and the _Main Guard_, and as the duties of the {106} Vanguard are reconnaissance in general, as well as the protection in particular of the Main Guard, it will contain a large proportion of mobile troops, with infantry for a.s.sault and resistance, and engineers for clearing the way through or over obstacles. Aircraft, in advance of the Vanguard, not only increase the area under search and expedite the discovery of the enemy, but prevent surprise and a.s.sist the Advanced Guard as a whole by close co-operation in feeling for and fighting the enemy when encountered. "In order to reconnoitre one must compel the enemy to show himself wherever he may be. To this end he has to be attacked until the extent of his position has been clearly defined. But the attack is made with the intention not to bring on an action. The skirmishing lines will advance, but they must be able to disengage themselves at a given moment. Pressure is exercised from a distance without allowing the forces exerting that pressure to become tied up" (Marshal Foch). The duty of the Main Guard is Resistance, that is to say, fighting. It will therefore consist mainly of infantry, with artillery and machine guns, and the troops will move in the order in which they will come into action. The Vanguard will be preceded by scouts, special attention being paid to roads and tracks parallel with the advance. This screen is followed by the remainder of the Vanguard, in collected formation, until it is in contact with or in the vicinity of the enemy, with protection at all times against local surprise. The Main Guard follows, in touch with the Vanguard, and with local protection. Both portions have definite commanders, and the commander of the whole Advanced Guard will probably move with the supports of the Vanguard. The commander will also determine the _relative distances_ between the Vanguard and the Main Guard, these being regulated by the strength of the Advanced Guard, and being based upon the necessity of one part supporting the other. The distance of the {107} Advanced Guard ahead of the Main Body may have been mentioned in the operation orders, but if it is left to the discretion of the Advanced Guard commander he will be guided solely by the interests of the force he is covering, and his decision will be influenced by the nature of the country (whether it is open, or intersected by woods, hedges, sunken roads, etc., which make observation even by aircraft a matter of great difficulty) and by the tactical situation, such distance being chosen as will suit these conditions, while admitting the fulfilment of the objects in view, viz.:--to obtain information concerning the enemy and to prevent hostile reconnaissance; to prevent surprise and delay; and to enable the Main Body to deploy into battle formation without interruption by the enemy's fire.

It is also the duty of the commander to ensure _communication_ between the various parts of the Advanced Guard and between that force and the Main Body, by arranging for mounted orderlies and cyclists, signallers and connecting files, in addition to the contact patrols furnished by the Air Service, and to such telegraphic and telephonic communication as can be provided in the field by the Signals. This is of the first importance, as the action of the commanders of the Advanced Guard and of the Main Body will depend on information received, and not only must information be gained by every available means, but it must also be communicated without delay to all concerned while it is fresh and before it becomes stale. It must also be remembered that negative information (_e.g._ that such and such a village has been thoroughly searched and no trace of the enemy found) is at least of equal value to positive information. The repet.i.tion or confirmation of information already sent are also of importance, as it is clearly of value to a commander to know positively that the enemy is still absent, or still present, at a certain time in a certain locality. In the American Civil War, during an encounter battle between {108} advanced troops, the commander of the cavalry of the United States Army held up the Confederate advanced troops. A sharp fight took place at _Sulphur Springs_ (October 12, 1863) and the United States cavalry commander became so absorbed in the battle that he failed to send information to headquarters, and General Meade did not learn that he was in contact with the Army of Northern Virginia until late in the afternoon. In the campaign of _Fredericksburg_, General R. E. Lee, with the Army of Northern Virginia, was confronted by General Burnside, with the Army of the Potomac. On November 15, 1862, a patrol of Confederate cavalry discovered Burnside's troops moving eastwards, and another patrol brought news the same day that gunboats and transports had entered Acguia Creek on the Potomac. These two pieces of information, collected at points 40 miles distant from one another, gave Lee an insight into his opponent's design. Information gained by aircraft on September 4 and 5, 1914, and communicated immediately to General Joffre, led to the discovery of the flank march across the Franco-British front by the German I. Army, and to the decisive counter-attack at the _First Battle of the Marne_ (September 6, 1914).

The Advanced Guard commander must be careful how he becomes seriously engaged, and must avoid any enterprise not strictly in accordance with the known intentions of the commander of the Main Body. The tendency to independent action of this kind, which militates against the success of the best laid plans, was very observable in the early battles of the Franco-Prussian War of 1870-1871. Actions were hastily entered on by Advanced Guards, maintained with varying success by the gradual arrival of reinforcements, and finally concluded with barren results and losses in excess of those inflicted. At the _Battle of Spicheren_ (August 6, 1870) the Advanced Guard of the 14th Prussian Division commenced the battle, which had to {109} be sustained for three hours by 11 battalions against 39. During the next three hours 8 more battalions arrived, and at the conclusion of the battle only 27 battalions and 10 batteries in all had come into action against a whole French Corps, and there were two French Corps within reach of the one engaged. Had these "marched to the sound of the cannon," as Napoleon would have marched, the 14th Prussian Division would have been unable to extricate itself without complete disaster. At the _Battle of Worth_ (August 6, 1870) the Prussian Crown Prince had expressed his intention not to engage the French on that day. Yet the Advanced Guard of the V. Corps brought on a battle into which the Bavarian Corps was perforce drawn. The Crown Prince sent word for the action to be discontinued, but the advanced troops were so seriously involved in the battle that reinforcements had to be sent into action. Although tactically successful the battle was out of accord with the settled plans of the Commander-in-Chief. In the same way the Advanced Guard of the VII. Prussian Corps, contrary to the letter and the spirit of the orders of the commander of the I. Army, precipitated an action at _Colombey_ (August 14, 1870). Other troops were drawn into the fight, and finally the whole of the I. Army was engaged in a battle which its commander not only disapproved but had expressly forbidden. The battle had no tactical or strategical results, and heavy losses were sustained on both sides. "Precipitate action of this kind prevents the troops being engaged in the most advantageous manner. For when a small force is engaged against a larger one it becomes necessary, as reinforcements arrive, to move them up to support some point already hard pressed, and the whole force is thus used up and disseminated, instead of being employed collectively where an effective blow may be struck. Thus the direction of the fight is surrendered to the enemy, as at Spicheren and Colombey. The French positions were so strong that the German {110} reinforcements as they arrived were frittered away in support of troops already engaged, and the state of the latter during the action was frequently very critical.

At Colombey the battle resolved itself into a desperate struggle along the front of the French position, where the Prussians made little impression, while their losses considerably exceeded those inflicted on the French" (Clery). It is thus seen that the commander of the Advanced Guard must limit his aggressive action in accordance with his instructions and with the tactical and strategical requirements of the force he is covering. But his action in _protecting_ the Main Body is unfettered by any considerations of prudence, and must ever be vigorous and resolute, any risks being taken that ensure the safety of the Main Body. On the morning of the _Battle of Nachod_ (June 27, 1866) the Advanced Guard of General Steinmetz's V. Corps (of the Army of the Crown Prince of Prussia) was in bivouacs on a plateau, after emerging from a long and narrow defile through which the Main Body must march to the open country beyond. About 8 a.m. the cavalry of the Vanguard was checked by the advanced troops of the VI. Austrian Corps. It was imperative that the Prussian Advanced Guard should hold the plateau until the Main Body had extricated itself from the defile. By the rapid and accurate fire of the infantry and horse artillery, and the co-operation of the cavalry against the Austrian squadrons, the thin line was maintained for more than three hours. Less than 7 battalions of infantry, with 13 squadrons of cavalry and 3 batteries of light artillery, kept in check 21 battalions, 11 squadrons, and 4 batteries.

Had the Advanced Guard suffered itself to be driven back on the Main Body in the defile a disaster could scarcely have been avoided, and owing to the steadfast endurance of the Advanced Guard the Main Body was able to drive the Austrian Corps from the field.

ADVANCED GUARD PROBLEMS.--The Advanced Guard commander must be able to appreciate without delay {111} the situation which confronts his force, and to solve the problem before him with regard solely to the interests of the force he is covering.

(a) If the Vanguard is held up by the enemy who is ascertained to be inferior in strength to the Advanced Guard, the commander will transmit information to the Main Body and will attack vigorously to disperse the enemy, in order that the movements of the Main Body may not be delayed.

A fire attack would be organised on the front of the enemy, supported by close-range artillery fire, and a turning movement with Lewis guns and rifles on one or both flanks. If the enemy held to a covered position they could be ejected by rifle bombers or light mortars from a flank, while artillery and machine guns prevented aimed fire at the attacking force.

(b) If fire is opened on the Vanguard and definite information as to the strength and dispositions of the enemy cannot be ascertained, such information as had been gained would be transmitted and a bold procedure would be adopted in order that the information might be supplemented as quickly as possible. The commander would reinforce his Vanguard with infantry from the Main Guard, and should be able to force the enemy to disclose his position and strength, but unless ordered to do so would take care not to become so involved in action that the Main Body would be compelled to come up and extricate them.

(c) If the enemy is encountered when the Advanced Guard commander knows that it is the intention of his superior to deliver an attack the information would be transmitted with an outline of the steps taken in seizing and securing all tactical points that will be of service to the Main Body. The Advanced Guard would work on a wider front than would otherwise be used by a force of that strength, and the artillery would be posted with a view to its position being adopted as the main artillery position.

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(d) If, under similar circ.u.mstances, the intention not to be drawn into a decisive engagement is known by the Advanced Guard commander he would limit his activities to reconnaissance of the enemy's position and numbers, and while hampering the enemy and preventing him from finding out particulars concerning the Main Body, he must take care not to become involved in a general engagement.

(e) A case may easily occur in which vigorous action is demanded, whether the commander of the Main Body intends to attack at once or to defer an engagement. Such a situation would arise if the Vanguard discovered the approach of the enemy towards a ridge or other position of tactical advantage, and if the Advanced Guard commander could, by a rapid advance, forestall the enemy in the occupation of such a position, his failure to do so, or hesitation in waiting for explicit orders to do so, would be a grave neglect of duty.

(f) In the American Civil War a tactical blunder of another kind, due to the impetuosity of the commander of the Independent Cavalry of the Army of Northern Virginia, prevented the Southern commander from obtaining a great strategical advantage over the Army of the Potomac.

The latter force had been withdrawn by General McClellan, after the Seven Days' Battle around Richmond, to a secure position at Malvern Hill, where the a.s.saults of the Army of Northern Virginia were beaten back with heavy losses. McClellan continued the withdrawal and had reached Harrison's Landing on the James River. The Independent Cavalry of the Southern Army had previously been dispatched on a false scent, but at 9 a.m. on July 3 touch was regained with the Northern forces, which were sighted from _Evelington Heights_ (July 3, 1862), a commanding ridge within two miles of the bivouacs of the Army of the Potomac, which was resting in apparent security, with inadequate precautions against surprise. General J. E. B. Stuart, the Confederate cavalry commander, {113} reached Evelington Heights with 1,200 sabres and carbines and one light howitzer, and the whole Army of the Potomac, 90,000 all arms, was in bivouacs in full view from the Heights, and it was clear that his presence was not suspected. The nearest column of the force he was covering was six miles away, and there remained about ten hours of daylight. It is easy to see, after the event, that this was a case where "Silence is golden." Stuart should have sent the information to Lee and to every column commander, urging them to press on at all speed, while he occupied the Heights with his dismounted men with the determination to hold his position with fire action, if discovered, until the arrival of one or more columns of the Army of Northern Virginia. But he failed to appreciate the situation, and forgetting the larger question, he seized the opportunity to spread panic in the ranks of the Army of the Potomac, and opened fire with his one light howitzer. The Northerners recovered from the panic caused by this unexpected attack, when it was realised that only one gun was in action against them, and attacked and captured the Heights, and were strongly entrenched there before the nearest Confederate column arrived.

(g) Among the examples of Advanced Guard work in Marshal Foch's "Principles of War" is a problem for a battalion as the Advanced Guard of a Brigade. "What is the problem the battalion commander has to solve? It consists in preparing for the brigade to go into action against an enemy who may debouch from Bettwiller. What does the brigade require for such an action? It requires the _s.p.a.ce_ necessary for the full employment of its forces, and the _time_ necessary for their arrival and deployment. In order to achieve that double task the battalion commander orders his troops to occupy _the whole s.p.a.ce necessary_, and places them in points where they may hold on for the _necessary time_."

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FLANK ATTACKS AND FLANK GUARDS

"A man thoroughly penetrated with the spirit of Napoleon's warfare would hardly fail to make his enemy's communications his first objective."---Col. G. F. R. HENDERSON.

The Flanks are the most vulnerable points of an army, for an attack upon these points subjects the defenders to enfilade fire, and is delivered by troops arrayed in attack formation against an enemy that is not in a position to repel the attack. The consequences of a successful Flank Attack are so far-reaching that every effort will be made by a commander to bring about such a consummation in order that he may sever his adversary's communications, bring him to the end of his resources, and deprive him of the means of replenishing them.

If, therefore, there is any possibility of a column on the march being attacked in flank a force must be detached to protect that flank, and if both flanks are exposed to attack both must be similarly protected.

The flank is the most vulnerable part of a moving column, and an attack driven home upon that part has every prospect of success, for it will be delivered by a force that is distributed in depth against a force that is protracted in width after changing front to meet the attack, and the absence of depth in the defending force will deprive the defence of the princ.i.p.al source of strength in resisting attack.

An independent column is liable to attack on either of its flanks, unless the nature of the country through which it is pa.s.sing provides security for one or the other in the form of an impenetrable feature (such as a wide, {115} trackless marsh), or an impa.s.sable barrier (such as a neutral frontier). The outer columns of a force moving on parallel routes will have an exposed flank, while their inner flank is protected by maintaining touch with the neighbouring column.

Flank Guards may be furnished by the Main Body, or by the Advanced Guard, and this point will be made clear in the orders for the operations. Their composition, strength, and distribution, and the interval at which they move on the flank of the Main Body, are similar to those of an Advanced Guard, while their action under all circ.u.mstances is governed by the same tactical considerations, the principle underlying every action of a Flank Guard commander being compliance with the known intentions of the commander of the Main Body, and the sacrifice of the interests of the Flank Guard to preserve the interests of the Main Body. The same duties of reconnaissance and protection have also to be carried out, and communication with the Main Body has to be maintained. For the purposes of reconnaissance and communication Aircraft are even more effective than in Advanced Guard work, while observation patrols supplement and confirm the reports of aerial observers. The work of protection varies with the nature of the country through which the Guard and the Main Body are moving at the particular time. In open country the Flank Guard may be keeping pace with the Main Body at a regularly maintained interval, and on parallel lines. In close country, and in hilly or mountainous districts, it may be necessary to occupy a successive series of tactical positions on the exposed flank, any of which can be reinforced and held at need to safeguard the pa.s.sage of the Main Body. In order that the whole column may be protected, from the head of the Main Body to the train in rear, unbroken touch must be maintained both with the Advanced and the Rear Guard, and incursions between these forces and itself must be prevented by the Flank Guard.

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In addition to the protection of a column on the march, Flank Guard work is of the highest importance on the Lines of Communications and in the protection of Convoys. On the _Lines of Communications_ raids from the air or land may always be expected in Manoeuvre Warfare, and one flank is usually more vulnerable than the other. A _Convoy_, when parked, is liable to attack from any quarter; and when on the march it may be a.s.sailed from any direction, especially when the adversary can detach mounted troops, or infantry rendered mobile by motor transport, or raiding bodies carried in Aircraft. Frequently, however, one flank only of the Lines of Communications is vulnerable owing to the geographical or tactical situation, and the work of protecting traffic or Convoys on the Lines of Communications is Flank Guard work, with due precautions against surprise from all quarters, the Main Guard remaining with the Convoy and securing its safe arrival at its destination, rather than seeking an encounter with the enemy. The most efficient way to protect a Convoy is to piquet the road daily with troops sent out from posts on the line; but when it is necessary to send a Convoy by a route which cannot be protected in this way a special escort must be provided. The commander of an escort will not engage the enemy if his task can be accomplished without fighting. If fighting is inevitable the enemy should be engaged as far from the Convoy as possible, and it will not be halted and parked, except as a last resort. In the case of mechanical transport the whole of the escort will be carried in motor vehicles, and except where parallel roads are in existence, little can be done to secure flank protection while on the move. A portion of such escort will move with the Convoy and a portion will be sent ahead to secure any bridges or defiles which have to be pa.s.sed, the outlet of any defile being secured before the Convoy is permitted to enter the defile. In the case of a horsed Convoy the escort will usually consist of infantry, with a proportion {117} of mobile troops. Small Advanced and Rear Guards will be detailed and sufficient men will be posted along the column to ensure order and easy communication. The remainder of the escort will usually move on that flank from which attack is most likely.

The far-ranging raid on the Lines of Communications was a notable feature of the American Civil War. It was freely employed on both sides and was often harmful to the object of the attack and usually profitable to the raiders, especially to those of the South, by reason of the replenishment of stores. General Turner Ashby, the dashing cavalry leader in the Shenandoah Valley, was a constant source of terror to the Northern Generals, and his death while protecting the movements to _Cross Keys_ (June 6, 1862) was a terrible blow to Stonewall Jackson, who employed his mounted troops with more skill than any other commander, Confederate or Federal. General R. E. Lee possessed a great cavalry leader in J. E. B. Stuart, "but cool-headed as he was, Lee appears to have been fascinated by the idea of throwing a great body of hors.e.m.e.n across his enemy's communications, spreading terror among his supply trains, cutting his telegraphs and destroying his magazines. Yet in hardly a single instance did such expeditions inflict more than temporary discomfort on the enemy; and the Confederate Armies were led more than once into false manoeuvres for want of the information which only the cavalry could supply. Lee at _Malvern Hill_ and _Gettysburg_, and, on the side of the North, Hooker at _Chancellorsville_, and Grant at _Spottsylvania_, owed defeat in great measure to the absence of their mounted troops on raiding excursions. In the Valley, on the contrary, success was made possible because Jackson kept his cavalry to its legitimate duty" (Henderson "Stonewall Jackson"). In the Russo-j.a.panese War a column of 500 Cossacks, under Colonel Madritov, made a bold raid on the communications of the j.a.panese I. Army in the last days of April, 1904.

The raid involved a {118} ride of 240 miles and was carried out in entire ignorance of the imminent attack upon General Zasulich's force by the j.a.panese I. Army at the _Battle of the Yalu_ (May 1, 1904). On arrival at his objective Colonel Madritov found nothing to attack, as the base of the j.a.panese I. Army had been shifted from the Korean frontier to a shorter sea base at the Yalu mouth. On his return he found his General in disordered flight, and had his small force been available at the Battle of the Yalu it could have protected the retreat to Hamatan and Feng-hw.a.n.g-cheng. Raids and attacks outside the centre of operations, however daring, have no permanent value.

In the South African War a disaster to a Convoy at _Sannah's Post_, or _Koorn Spruit_ (March 31, 1900), was caused by the absence of precautions in front of a retreating force, the wagons being permitted to enter a defile (the Spruit crossed the road at right-angles and was held by the Boers) before the exit had been secured. Earlier in the same campaign a Convoy of 800 wagons was lost at _Ramdam_ (February 13, 1900). An ambushed force of Boers killed all the transport animals and the wagons were abandoned. No escort had been provided for the Convoy, which entered the ambushed area without previous reconnaissance.

Throughout the South African War the activities of De Wet emphasised the vulnerability of the Lines of Communications.

Where the tactical situation permits, arrangements should be made to protect the Lines of Communications by offensive action. An engagement may be invited in a suitable position, the protecting troops holding the raiders with a Delaying Action while reinforcements are summoned to converge on the battlefield for the purpose of surrounding and exterminating the raiders.

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THE REAR GUARD

A Rear Guard is essential to a force advancing in order to pick up the stragglers, to keep off marauders, and to prevent surprise by an energetic enemy who may detach a force for a surprise attack on the rear of the advancing column.

But its most important work is the protection of a retreating force, and this work will vary in difficulty with the freshness and enterprise of the enemy and the spirit and determination of the force that is being pursued. Generally speaking, Rear Guard fighting against an unexhausted enemy is the most difficult and most dangerous of all military enterprises. When a Rear Guard halts to fight it is being separated every minute from the Main Body, which is moving away from it, while every minute brings reinforcements to the enemy. The work requires great tactical skill, as it is the duty of the commander to delay pursuit by occupying positions from which he withdraws at the last moment, without becoming involved in a general engagement, from the meshes of which it may be necessary for the Main Body to return and extricate him. The work also requires great moral courage, as it is the duty of the commander to risk the loss of his force if by so doing he is adopting the only means of saving the Main Body.

STRENGTH.--The strength of the Rear Guard will depend upon the energy, strength, and closeness of the pursuit, the condition of the Main Body (and whether it is withdrawing voluntarily or upon compulsion after an unsuccessful engagement) and upon the nature of the country, but it will generally amount to not less than {120} one-fifth or more than one-third of the whole force, and will be selected, as a rule, from those who have been least severely engaged.

COMPOSITION.--Its composition depends upon the work to be performed, and this calls for detachments of all arms of the land service, in addition to _Aircraft_, which can prevent surprise by reconnaissance over the hostile area and can hara.s.s the pursuing columns by day and by night by fire-action with Lewis guns and bombs. _Mounted troops_ are required to extend the area watched and to prolong the resistance by reason of their superior mobility, in addition to their counter-action as cavalry. _Artillery_ are required to open long-range fire on the enemy's columns and so to cause delay by deployment; and to concentrate upon them while in, or emerging from, a defile. _Infantry_ and _Machine-gun Platoons_ are required for prolonged fire-fights and local counter-attacks, during which sudden bursts of machine and Lewis-gun fire will do the greatest execution. _Engineers_ provide sappers for the creation of obstacles and traps, and for the demolition of bridges and viaducts. _Mechanical Transport_ may be required to add to the mobility of the infantry. The _Medical Service_ is called upon to provide attention and ambulances for the wounded and for the sick and worn-out troops.

DISTRIBUTION.--The Rear Guard is divided into two parts--the Rear Party and the Main Guard. The _Rear Party_ consists, like the Vanguard of the Advanced Guard, of patrols and supports; the rest of the force forms the _Main Guard_, and marches in the order in which the troops are required, viz.: Artillery (with escort), Mounted Troops (if any remain over from the Rear Party), Infantry, Medical Services and Ambulances, and the Sappers of the Royal Engineers. The guns can thus open fire whenever required, and the sappers, who are furthest away from the pursuit, will have the longer time to prepare obstacles and demolitions, the {121} latter being completed by the Rear Party.

Communication must always be secured and maintained between the Rear Party and the Main Guard, and between the Rear Guard and the Main Body.

DISTANCE.--The distance at which the Rear Guard works is governed by the duty it has to perform, viz.: to permit the withdrawal of the Main Body to be carried out without interruption by the enemy, and to effect this it will usually be necessary for the Machine Gun and Infantry Platoons of the Main Guard to keep within effective range of positions from which hostile artillery might molest the Main Body. The commander will probably remain with this part of his force, as its work is of the highest importance; in any case his position must be made known and there should be definite commanders of the Rear Party and the Main Guard. But while the distance separating the Rear Guard from the Main Body must be sufficient, it must not be too great, or the enemy may penetrate between it and the Main Body, and not only will the Rear Guard be cut off and liable to destruction but it will cease to protect the Main Body.

TACTICAL PRINCIPLES.--The tactical work of a Rear Guard is carried out according to the following principles:--

_The Rear Party watches_, and it must watch _all_ the roads and tracks by which the pursuing force can advance, and is responsible that the enemy does not get round the flanks (which may or may not be specially protected by Flank Guards). Reconnaissance by Aircraft for the discovery of intended outflanking movements is probably of greater value in Rear Guard work than in any other military action. The Rear Party also resists the hostile advanced troops as long as possible, withdrawing before it is outflanked. "An outflanking manoeuvre is specially convenient when attacking a Rear Guard, for the latter cannot fulfil its mission once it has been turned" (Marshal Foch).

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_The Main Guard fights for time_. If the withdrawal is more or less unmolested, or if such pursuit as is offered can be dealt with by the Rear Party, the Main Guard can continue its march, taking care not to close in on the Main Body; and while falling back it can demolish bridges, create obstacles, prepare ambushes, and so on, employing all devices (within the laws of war) for delaying the enemy. When hotly pursued it must gain time at all costs for the army it is covering, and must not allow itself to be driven back on to the Main Body; or it will hamper that force and cease to protect it. Time can be gained by compelling the enemy to halt to reconnoitre a position, by making him deploy into attack formation, and by making him go out of his way in order to envelop a flank. But before an attack reaches a position in such strength as to ensure success, and before the enveloping force can achieve its object, sub-divisions of the Main Guard will withdraw in succession under covering fire from those still in the line, which also withdraw in their turn under covering fire from the sub-divisions in their new positions, to tactical points further back, from which again they cover the withdrawal of the forces which had protected their own movement.

Certain points must be noted about the positions chosen for these successive fire-fights, and the choice of the positions is so difficult that an experienced staff officer should be specially detailed for the work, Positions chosen must be in the enemy's way and the lines of withdrawal to them must not converge; they must be easy to defend and difficult to attack; the flanks must be secure from direct attack and effective enfilade fire, necessitating a wide detour (and consequent gain of time from the enemy) before they can be threatened; long-range artillery fire on the lines of approach should be possible in order to delay and break up the enemy's advance; and each position chosen for the next line of resistance should be unseen by the {123} pursuing enemy, and sufficiently far away from the line last occupied to induce him to resume his march formation. This will necessitate a repet.i.tion on the part of the enemy of all the stages of the attack--the discovery and the report on the position, the decision to attack, and the deployment into attack formation. It will often be of advantage for a Rear Guard to take up a delaying position one or two hours before dark, as the enemy will then have to attack with darkness approaching and may wish to defer the attack until daylight, thus gaining several hours for the protected force.

"The first position taken up by a Rear Guard after an unsuccessful fight must be held longer, as a rule, than the subsequent positions, because when once the defeated army has got well away along the roads and has regained some semblance of organisation, the march continues without interruption unless some obstacle has to be crossed" (General Haking, "Staff Rides"). It can also be noted that as it is seldom the intention of the Rear Guard commander to deliver a decisive counter-attack, he can detail a very large proportion of his force to hold the successive positions, with local reserves, for purely local counter-attacks; and for the same reason, an obstacle in front of his position (which would make that position unsuitable for the Active Defence, as it would prevent the advance of the General Reserve to the decisive counter-attack) is most welcome in the Delaying Action of a Rear Guard fighting for time for its Main Body.

When at length a line of resistance is evacuated, the heavy artillery will be withdrawn first to move to a distant fire position, then the slow moving infantry and the light artillery (under the protective fire of the aircraft and mobile troops), and last the cavalry and other mobile troops, who by reason of their superior mobility, can hang on to the last and can protect the flanks of the Rear Guard as they fall back, before {124} resuming their work as a Rear Party, observing and resisting the advanced troops of the pursuing force.

During a close pursuit the Rear Guard commander will be called upon to exercise all his faculties and to exert all his tactical ability in handling his command. One of the most anxious times before him will be when the Main Body is pa.s.sing through a defile, as such a pa.s.sage will not only delay its march but will make its columns particularly vulnerable and helpless. In the case of defiles Napoleon's maxim must be borne in mind: "It is contrary to the principles of war to let one's parks and heavy artillery enter a defile if the other end is not held also." At _Sannah's Post_ (March 31, 1900) the train was permitted to enter a defile caused by the banks of the Koorn River without the previous occupation of that defile, and all the wagons were captured.

This not only emphasises the necessity for an Advanced Guard in retreat, but points to the need of tactical knowledge on the part of the Rear Guard commander, especially in mountainous country or in terrain cut up by woods and marshes, where the train is liable to cause delays, as the withdrawing force is compelled to march in a long drawn column. Extra time must be gained by the Main Guard to enable the Main Body to emerge from the defile. The Rear Guard commander must therefore adapt his plans to suit the country through which the Main Body has to pa.s.s, as well as the country in which he will himself fight Delaying Actions. A good map and ability to use it, and close co-operation with the Main Body, must be determining factors for success or failure.

TRAINING.--When troops are being exercised in Rear Guard work opportunities should be taken to explain the difficulties of choosing suitable positions, of withdrawing from them when involved in battle, of the paramount necessity for mutual support, and of accepting {125} any risk that may be required to safeguard the Main Body. Stress should be laid upon the importance of Fire Tactics (the judicious combination of Fire and Movement), the greatest of all factors in a successful Rear Guard battle, and upon the ability to read and understand a map, an essential qualification in all movements of troops and indispensable in Rear Guard fighting. From the map a platoon commander must be able to predict the probable line of the enemy's advance against the line of resistance as well as the best route to be taken when, at length, he withdraws his platoon to another fire position in rear; while he must be prepared to throw his platoon in local counter-attack on the flank or rear of an a.s.saulting party that has become detached from its supports and therefore affords a fleeting opportunity for a local fighting success, and a rapid advance for this purpose along a route unseen to the foe, a speedy reorganisation after victory, and a rapid withdrawal to the point of issue, or to a line in rear, can best be achieved by use of the map and reconnaissance of the ground of the encounter.

EYE FOR GROUND.--One of the secrets of Napoleon's extraordinary successes was his "eye for ground." "It was not until I went to Jena and Austerlitz that I really grasped what an important part an eye for ground like Napoleon's, or blindness as to ground like his opponent's at both those battles, may play in Grand Tactics, that is, the art of generalship" (Colonel G. F. R. Henderson, "The Science of War"). The same was true of General R. E. Lee, particularly in the Wilderness Campaign, when it was not only the entrenchments but the natural features of the ground on which he relied in his defensive tactics.