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 harass 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 repetition
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 passing through a defile, as such a passage 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 pass, 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 assaulting 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.
"His eye for ground must have been extraordinary. The campaign was
fought over a very large area, an area of very close country, with few
marked natural features; and yet in the midst of woods, jungles, and
streams, with very little time at his disposal, he always seems to have
selected positions than which none could have been stronger" (Colonel
G. F. R. Henderson, "The Science of War").
EXAMPLES OF REAR GUARD WORK.--During the Retreat from Mons the Rear
Guard of the II. Corps of the British Expeditionary Force delayed the
pursuit by the daring and devotion of its cavalry and artillery, and by
subordinating its plans to the interests of the Main Body enabled the
Corps Commander (General Sir H. Smith-Dorrien) not only to throw off
the pursuit but to effect a junction with the other wing of the British
Army. The retreat took place after the First _Battle of Le Cateau_
(August 26, 1914), and during the period of the retreat the insecurity
of the British Army through the breakdown of a co-operating force
rendered it liable to disaster. But the moral of Marshal French and
his commanders, the stubborn fighting instincts of the British race,
and the excellence of the musketry training of the Regular Army in
times of peace, prevented the retreat from becoming a rout. The care
taken in training the troops in Fire Tactics, and particularly in
reloading with "eyes on the mark and butts to the shoulder," was most
abundantly justified. The accuracy and volume of the rifle fire
deceived the enemy as to the nature of the troops employed against
them, and the dismounted troops and infantry with their rifles were
reported as "battalions of machine gunners."
During the _Second Battle of the Somme_ (March, 1918), the British III,
and V. Armies fought a series of Rear Guard battles, and the enemy's
advance was made at a very heavy cost. "Units retreated stubbornly
from one position to another as they found them turned and threatened
with isolation; but at many points fierce engagements were fought, and
whenever the enemy attempted a frontal attack he was beaten off with
loss" (Sir D. Haig's Dispatches). The machine gun proved its
effectiveness again and again during the British {127} withdrawal, and
twelve machine guns of the 63rd Division, posted in _Les Boeufs_ (March
24, 1918), held up the enemy's advance from Morval at a critical
period, and enabled the division to reach the position assigned to it.
The losses inflicted on the enemy by machine-gun and rifle and
Lewis-gun bullets were so heavy that by March 25 Von Below's XVII. Army
was described in German dispatches as "quite exhausted." During the
same battle a detachment of about 100 officers and other ranks, under
the command of the Brigade-Major of the 61st Brigade, held the enemy at
bay from early morning until 6 p.m. at _Le Quesnoy_ (March 27, 1918)
and enabled the 20th Division to retire to its destined position.
At the _Combat of Roliça_ (August 17, 1808) the French General
Delaborde was outnumbered by the Anglo-Portuguese forces under Sir A.
Wellesley, and being driven from his first and second positions he
withdrew to the mountains. During his retreat "he brought every arm
into action at the proper time . . . and retreated by alternative
masses, protecting his movements by short, vigorous charges of cavalry
. . . and he fell back, disputing the ground, to Quinta de Bugagliera"
(Napier).
In December, 1808, and January, 1809, General Sir John Moore withdrew
to Coruña before the armies of Napoleon (and when the Emperor returned
to Madrid, before those of Marshal Soult). "He conducted his long and
arduous retreat with sagacity, intelligence, and fortitude" (Napier),
and it is interesting to note that as in the Retreat from Mons in 1914
and at the Second Battle of the Somme in 1918, so in the rear-guard
actions which preceded the embarkation of Sir John Moore's Army, the
musketry of the British troops was the deciding factor: "the English
muskets were all new, the ammunition fresh; and whether from the
peculiar construction of the muskets, the physical strength and
coolness of the men, or all combined, {128} the English fire is the
most destructive known" (Napier).
At _Bristow Station_ (October 14, 1863) during General Meade's campaign
in Northern Virginia (after his defeat of General Lee at Gettysburg,
July 1-3, 1863), a surprise attack by Stuart's cavalry and infantry
from General Rode's Division caused the withdrawal of the Federal
troops. General Warren covered the retirement and eventually withdrew
his own forces unmolested after beating off several attacks with
close-range musket fire.
Jean Victor Moreau, one of the greatest generals of the French
Republic, became a general of division at the age of 33, and by his
skill in extricating his forces from apparently certain disaster
established in retreat a far greater reputation for generalship than
his brilliant victories secured for him. In the spring of 1796 he
defeated Latour at _Rastatt_ and the Archduke Charles at _Ettlingen_,
and drove the Austrians back to the Danube, but owing to the defeat and
retreat of Jourdan he was compelled to regain the Rhine in a desperate
and apparently hopeless effort. Yet he not only preserved his army
intact but brought with him over 5,000 prisoners. In 1798 he again
saved his army from destruction when hard pressed by the Russians and
Austrians in Italy. Retreat was by no means his only or favourite
manoeuvre, as he subsequently gained victory after victory over the
Austrians in the campaign of 1800, drove them back behind the River
Inn, and won the decisive victory of _Hohenlinden_ (December 3, 1800),
where the Austrians and their Bavarian allies lost 17,000 men and 74
guns against a total loss of 5,000 on the side of the French.
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