LAND AND WATER 
January 2, 1915. 
then everything will depend upon your having 
enough men to hold the lines as against the num- 
ber of men he can bring against you. And the 
problem here is not a mere question of proportion 
(as, that one man behind earth can hold up three 
men, or five men, attacking him), it is also a ques- 
tion of absolute numbers. 
To put an extreme case: The Roman Wall 
across North Britain is an example of " lines." 
Suppose ten men tried to hold it against fifty, their 
effort would be manifestly ridiculous. Ten men 
could not hold it against ten, let alone against 
fifty, because ten men are not sufficient to watch 
any force at all that was free to operate against a 
front stretching from Carlisle to Newcastle. Ten 
men could not " hold " the Wall at all. Con- 
versely, a million men with proper artillery could 
hold those " lines," not against three million or 
five million, but against any number of millions. 
Because the enemy, however numerous, could not 
deploy a sufficient number of men at any one spot 
to break down the solid defence which so very 
large a body as a million could, with proper com- 
munications, concentrate wherever an attack 
threatened. 
The piercing of entrenched " lines," therefore, 
depends in the main upon this mathematical con- 
ception. 
" When the defenders of a ' line ' have become 
so rare that they cannot concentrate on any point 
whatever in a given time, men sufficient to stop 
such numbers as the enemy can (a) usefully deploy 
(b) concentrate on that point in the same given 
time — then the ' line ' is pierced," and once 
pierced its whole structure disappears. It must 
either retire precipitately or suffer disaster. For 
instance, twenty men could not hold a mile of wall 
against 100 men trying to scale it by ladders. 
Somewhere in the rushes to and fro a party of the 
hundred would get up. 
Suppose 1,000 men could just hold it against 
5,000. That would be because 1,000 was enough 
to " man " the wall, i.e., enough to concentrate a 
group of ten or so in any point and push the ladder 
off. But 500 would leave gaps. Six hundred could 
not hold it at all, quite irrespective of whether the 
assailants were 5,000 or 3,000 or 2,000. And once 
a body of the assailants scaled a bit of the wall the 
whole organisation of its defence must collapse. 
A warfare of " lines," therefore, is essentially 
one in which the attackers wear down in numbers 
and material resources the besieged ; the besieged 
have not an indefinite power of resistance, but 
must, after a certain amount of wearing down, 
break. 
That is why the whole thing is compared to the 
Strain put upon a very hard, but at the same time 
brittle, substance such as a rod of glass, and that 
is why a reserve is kept back to strike at the right 
moment, as a hammer might strike just at the 
right moment upon a glass rod already strained 
by the hands. 
Critics sometimes talk as though the existence 
of trenches behind trenches, that is of a series of 
" lines," parallel one with another behind the 
original " line," rendered the problem in- 
soluble. "The enemy," they say, "may be 
driven out of his first 'line,' but he will 
fall back upon his second; from his second 
upon his third — and so fortli. There is no end to 
it." But that is not the way the thing works, or 
can conceivably work, unless the second lines arB. 
shorter than the first and the third lines shorter 
than the second. So long as a General has enough' 
men to hold his first line against the enemy's num- 
bers and mechanical means of attack, so long ho 
will hold that first line. When he has no longer 
enough numbers to hold his first line he is mani- 
festly equally unable to hold a second line of the 
same length. He can only usefully fall back on a" 
second line on condition (he second line is shorter 
than the first. 
One could put the whole thing in a phrase by 
saying that an army is not " pushed " back from its 
lines, it is " threatened with the breaking " of its 
lines. 
The effort which you make against an en- 
trenched army is not like the effort which you 
make in shoving a door open against opposition; 
it is like the effort you might make in grinding at 
various parts of a long cord. If a man whose 
business it was to keep a cord stretched against 
you found your attrition making it grow so thin 
in places that it would not hold, he might move 
it rapidly back, sever the weak places and knot 
them up again ; but he could only do this on condi- 
tion that the new line to v»^hich he had retired, and 
which he proposed to hold with his cord, was 
shorter than the old one. 
The point is exceedingly elementary and 
therefore calls for an apology, but it is so much 
misunderstood at the present moment, and, mis- 
understanding breeds at home such a lack of con- 
fidence in the future of this trench fin;htin2: in 
France and Belgium, that it is well worth insisting 
upon. 
We have here an isthmus between two seas, 
--S ^-^F. 
II 
or a plain of open land between two moun- 
tain ranges, or belligerent territory between two 
neutral frontiers, or any other kind of issue re- 
quiring artificial defence between two natural 
obstacles. 
It is defended by a General of country F 
against the invasion of forces from country E. 
To defend this issue and to prevent an enemy 
from E penetrating towards F in the direction of the 
arrow, the General draws up his entrenched lines, 
A-B, sufficient for the defence of which (but only 
just sufficient) are his sixteen units — which I have 
represented by sixteen dots — holding the lines. 
His wastage in men, or the corresponding increase 
of his enemies, whether in numbers or in mechani- 
cal opportunities for attack, reducing his sixteen 
to the value of ten his lines are lost. They cannot 
be held with only ten units remaining. Why^ 
Because they are too long. 
It is no good preparing behind those lines, 
A-B, another series of lines, C-D. The ten v/hom 
he has left will not be strong enough to hold C-D 
