April 25, 19 1 8 
Land & Water 
Battle of the Lys : By Hilaire Belloc 
The 7th to the 14th days 
BEFORE describing the details of the great 
action in the valley of the Lys as it has developed 
during the past week, it may be well to put 
simply and in diagrammatic form the enemy's 
past and present situation. 
Before he attacked upon this sector he found the Allied 
armies (here almost entirely British, save for the Belgian 
forces north of Ypres and one Portuguese division in front 
of Lille) occupying a big right-angled comer of land which 
is that of the French side of the Straits of Dover. Each 
side of this angle was roughly 50 miles long. North of 
Abbeville the only way out of it was by sea and the only 
three effective ports open were Dunkirk, Calais and Boulogne. 
This main group of the British forces relied for its supply 
from the sea — apart from roads — upon railways passing through 
Abbeville and Amiens from west and south-east on railways 
coming from Boulogne, Calais and Dunkirk upon the coast 
immediately Sehind. All the?e railways passed through the 
junctions of Bethune and Hazebrouck and through that of 
Bethune ran all the direct communications with tlie south, 
that is with the French. 
When the enemy struck on April gth, a fortnight ago, 
upon that sector of the front lying beyond the points 2 and 
3 upon diagram i, his object was to seize Bethune immediately; 
in the next move Hazebrouck, and so before there could 
possibly be time to organise a retirement from all the north- 
eastern part of the district, to cut the communications at 
the nodal points and throw out of action all this part of the 
Allied forces. How far such rapid rupture would have 
proceeded we cannot tell, but we may be certain that it 
would have destroyed, principally by way of capture, every- 
thing to east of the line Dunkirk, Hazebrouck, Bdthune. 
It would probably have overrun the whole of the belt 
to the sea, for the opportunities of resoldering the line after 
that bre^k through would have been less than they were 
in the south a month ago ; there would have been no room 
for manoeuvre and no sufficient opportunity even for retiring 
any appreciable proportion of the forces by way of the sea- 
ports behind. 
As we know, so complete a success was happily denied the 
enemy. He broke through, indeed, upon the sector 2-3, 
but he failed to reach Bethune altogether. He was held 
by the Lancashire men at the comer of the point 3, which 
is Givenchy. His advarice through this check took the form, 
after about eleven days fighting, of a large bulge, very much 
the same in shape as the great salient he had formed to the 
south before Amiens : This similarity of shape we will discuss 
in a later article. It is not an accident but it has its defin- 
able causes. As men were rapidly pushed up to the menaced 
districts his advance was further checked. The shape of the 
new area he held upon the nth day of the fighting may be 
reduced to a triangle, although the actual shape of the front 
was, of course, sinuous and complicated. This triangle I have 
marked on the diagram 1-2-3, <^he apex i being in front of 
the little town of Merville which he holds. 
In such a situation and after so great a lapse of time he 
could no longer hope for anything like a decisive result. 
But he could hope to effect ultimately a change in the dispo- 
sition of the Allies greatly to his advantage, and that change 
may be called the swinging back of the Allied line pivoting 
upon Arras to the line of the Aa river. This would have 
involved a complete abandonment of all the north-eastern 
square in which Dunkirk and the ruins of Ypres stand, and 
even if that abandonment were conducted in complete order, 
the final result would have the following great disadvantages 
for the French and British. 
(i) The port of Dunkirk would be in the enemy's hands, 
putting him much nearer the Straits of Dover than he had 
yet been. 
(2) A different salient would have been created round 
.4rras, which salient he might hope to reduce as it would 
be a long time before the new defensive could be strongly 
organised. 
(3) J He would have found himself, then, within but a 
short distance of Calais, about ten miles, able to molest 
that harbour with his heavy pieces and probably to close 
it altogether. 
(4) He would have produced an Allied defensive line 
possessing no lateral communications save the distant one 
along the sea coast. 
(5) He would have reduced to still narrower and very 
perilous limits the margin of manoeuvre remaining to the 
Allied forces here in the north against the Channel. In other 
words, every further advance of his would have meant 
disorder and with that disaster, not only the loss of great 
numbers to the Allied side, but the possession by him of the 
Channel ports. 
Now, to compel the swinging back of the line thus to the 
line of the Aa river— a good line of defence, so far as it goes, 
with excellent observation behind it from the hills, and a 
perfectly straight marshy line to defend, better even than 
that of the Yser— two forms of action from the triangle 
which he occupied, two forms the success of either of which 
singly would go far to achieve his end, and the success of 
which both together would certainly achieve it, lay before 
him. These forms of action consist in pushing forward 
along the north front of the triangle 1-2 and along the south 
front 1-3. The first would ultimately give him the line of 
heights M-K— that is, from Mont des Cats to Kemmel, the 
junction at Hazebrouck, and the hill of Cassel. Long before 
these were fully held, from the moment their occupation 
seemed probable, retirement back along the coast would 
have had to begin. On the other front, from i to 3, his 
advance would give him the junction of Bethune, and begin 
to create a pronounced and dangerous salient at Arras. 
This action, with both elbows alternately upon the northern 
and southern front of the triangle to which he has been 
confined by the increasing resistance of the defence, is some- 
times and quite properly called "an attempt to enlarge his 
salient." It is that. And the enlargement of a salient 
both gives you more room for action and increases the length 
of shaken front upon which you are working. But a mere 
enlargement of the salient is no final strategic aim. The 
final aim was to compel the swinging back of the whole 
Allied line at the very least to this next possible defensive 
position of the Aa, with all its inconveniences and perils. 
Thus it is that we find him spending in proportion to the 
front attacked such enormous forces in trying to reach and 
occupy (probably by turning them to the right and to the 
left) the hills from M to K and to seize Hazebrouck. In 
other words, that is why you see him in the past week striking 
so furiously upon the front 1-2, while the complementary 
design of seizing Bethune explains the other co-relative 
action alternating with the first upon the Hne 1-3. 
With this in mind, we may turn to_the details of the last 
