THE LOCAL SITUATION. THE LOCAL DEFENCES.
[Sidenote: Zeebrugge Mole]
The village of Zeebrugge stands near the entrance to the
Zeebrugge-Bruges canal. At about half a mile inland from the coast at
Zeebrugge the canal lock was situated. To seaward of the lock, the
entrance channel, being open to the sea, was tidal. On the eastern
side of the entrance channel, about midway between the lock and the
coast-line, a small tidal harbour had been constructed for the use of
fishing craft. This tidal harbour was of no special value for naval
purposes, owing to its small depth. From the coast-line the entrance
channel was continued into the sea for a distance of about two hundred
and seventy yards by means of estacades--i.e., wooden piers. These
piers, curving outwards from the shore, are conspicuous in the
illustrations. For the purpose of protecting the canal entrance from
rough seas, which might interfere with the passage of vessels to and
from the canal, the famous Zeebrugge Mole had been constructed for the
Belgians. Semi-circular in shape, it emanated from the shore at a
distance of about half a mile to the westward of the canal entrance;
thence it curved round to the northward and eastward. This curved Mole
protected a roadstead, of some three hundred acres in extent, from
northerly and westerly gales. Easterly winds did not cause such heavy
seas as those from the directions already named owing to the protection
afforded by the Netherlands coast.
[Illustration: PORT OF ZEEBRUGGE]
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The construction of the Mole was a colossal task. There are no similar
works of such magnitude in Great Britain or the United States. When
lecturing in the latter country I always made a point of emphasising
that fact to our American cousins; their unfailing humour never failed
to appreciate this little friendly "dig."
The total length of the Mole was over one and a half miles. For
purposes of description it may be divided into four portions.
Commencing at the shoreward end, the first portion of the Mole took the
form of a stone railway pier built into the sea for a distance of two
hundred and fifty yards. This pier was connected to the second
portion, which consisted of an iron-piled railway viaduct three hundred
and thirty yards in length. This, in turn, was connected to the third
portion, which formed the Mole proper. The latter was built of
concrete blocks on its seaward and shore sides, the central part being
filled with gravel and paved with granite. The width of this portion
of the Mole was no less than eighty-one yards, and its length about
eighteen hundred and seventy-five, or rather over a land mile. At its
northeastern end, the fourth portion consisted of an extension piece,
two hundred and sixty yards long and fifteen feet broad, with a
lighthouse at its eastern extremity.
If the Mole had been constructed solid throughout its entire length,
the task of keeping the channel, leading to the canal entrance, or the
roadstead, at a convenient depth would have been impossible owing to
silt.
Silt may be defined as the movement of sand or mud, according to the
nature of the sea bottom in the {24} locality, due to current. The
bottom of the sea in this locality was sand. The current off the
Flanders coast is caused by tide--it is usually spoken of as tidal
stream. Tidal streams reverse their direction of movement about every
six hours. Now the movement of sand caused by a tidal stream tends to
deposit that sand in or against any irregularity with which it meets,
whether the latter is a groove on the sea bed or an obstacle such as a
wreck. This deposit first takes place from one direction, and then,
when the tidal stream reverses, from the opposite direction. It will
therefore be seen that, where a channel is artificially cut on the
floor of the sea, silt will continually tend to fill that channel again
until the bottom is level once more. And a ship which grounds in a
locality affected by silt will have sand deposited against her sides
much to the detriment of salvage operations. These facts are well
enough known to seamen and have an important bearing on this narrative.
[Sidenote: Concerning Silt]
Suppose for a moment that the entire Mole had been built in solid
formation--i.e., that the tidal stream had no free passage under the
viaduct. The west-going stream would tend to carry sand into the
roadstead between the Mole and the canal entrance, whereas the
east-going stream would be unable to remove the deposit a few hours
later. Thus the roadstead would soon have become useless, and access
to the canal would have been impracticable.
The sand along the whole Flanders coast was extremely susceptible to
movement. Such tendency was partially countered by the extensive use
of groynes. These latter, however, could not be carried {25} very far
out into the sea owing to the difficulties of construction and repair.
There were, therefore, no artificial barriers to prevent the movement
of the sand to the eastward or westward beyond a short distance from
the shore. Hence the necessity for keeping a portion of the Mole open
to allow the tidal stream to flow in both directions. Even so, a large
shoal had formed in the roadstead, and reduced the acreage available
for anchorage purposes.
When first designed the open viaduct was of shorter length than that
eventually constructed; the alteration was considered necessary after
local experience of the silt had been obtained. The iron piles, or
pillars, on which the viaduct was supported were of great strength and
much interlaced with steel rods to allow for severe buffeting in heavy
gales and to take the strain of railway traffic. A portion was
actually demolished by a gale when under construction, and the
completion of the Mole was consequently delayed for many months.
When making enquiries in search of expert advice on questions of
salvage, I had an interesting conversation with an individual who had
had considerable experience in salving vessels in other waters. Maybe
this book will remind him of our discussion. In his opinion salvage
work presented no great difficulties. It was only a matter of
obtaining the necessary apparatus, he thought, and any
vessel--concrete-filled or otherwise--could be removed in a month or
so. "How about silt?" I asked.
"Oh, silt shouldn't make much difference," he replied, and added, "but
we have no silt to speak of in that part of the world, so I cannot say
for certain."
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We then discussed the possibilities of salving a blockship at
Zeebrugge, for he had been informed of the proposed operation.
Eventually our conversation nearly resulted in a wager; that we came to
no terms was perhaps due to the fact that payment might have
necessitated application to a war widow.
The first and second portions of the Mole had not been materially
altered by the Germans during their occupation.
[Sidenote: The Outer Wall and the Parapet]
The third portion of the Mole will require detailed description. In
peace days the Mole had been used as a commercial wharf as well as a
breakwater. Ships used to secure alongside its inner wall. All the
necessary facilities, such as bollards for securing hawsers, fixed and
travelling cranes for loading or unloading cargo, and arrangements for
embarking passengers, had been provided. A large railway passenger
station, nearly two hundred yards long, was situated near its
southwestern end; a goods station and a coal shed, both very large
buildings, stood further to the northeastward. The floor level of this
portion of the Mole was about nine feet above the level of high tide.
On the outer (seaward) side a high wall, of great strength and
thickness, had been constructed for the purpose of preventing rough
seas from breaking over the Mole and damaging the sheds or washing away
the railway. The top of this wall was twenty feet above the floor
level of the Mole and therefore twenty-nine feet above the level of
high tide: at low tide it towered forty-four feet above the sea.
The fourth portion of the Mole was really formed by a continuation of
the outer wall, which extended beyond the third portion to the
lighthouse.
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The appearance of all portions of the outer wall, as viewed by anybody
situated in a boat alongside it, was exactly similar throughout its
entire length from the lighthouse to the railway viaduct. Thus the
individual in the boat, except in the unlikely event of being able to
see over the top of the wall, would be unable to tell, at all
definitely, whereabouts his boat was situated relative to objects on
the Mole. But this fact had not been accidentally overlooked by the
designer of the Mole; there was no object in taking it into
consideration, for there was then no idea of any vessel berthing
alongside the outer wall. For instance, there were no bollards, no
cranes, no capstans for working hawsers, in fact no arrangements
whatever for berthing a ship. I have already stated that this outer
wall was of great thickness, varying from twenty-five feet on the sea
bottom to ten feet in that portion standing above the floor level of
the Mole. Four feet below the top of the wall there was a pathway,
nine feet broad, running the whole length of the wall. This pathway
was known as the parapet. The parapet was bounded on its seaward side
by the four-foot wall just mentioned; on its inner side iron railings,
three feet high, were placed to prevent anybody falling from the
pathway to the floor of the Mole sixteen feet below. Flights of steps
led up from the Mole floor to the parapet, but these flights were very
few and far between.
That portion of the outer wall which formed the lighthouse extension of
the Mole was broadened, above the sea level, to about seventeen feet
throughout its length. The pathway was similar to that just described,
but fifteen feet in width. This portion of {28} the Mole was hollow, a
tunnel inside it running from the third portion of the Mole to the base
of the lighthouse.
The navigable channel from the open sea to the canal entrance could
only be maintained in an efficient state by means of continual
dredging, owing to the silt. The channel passed close to the
lighthouse at the end of the Mole, and then in a fairly direct line,
for a distance of three-quarters of a mile, to a position midway
between the extremities of the two piers marking the canal entrance.
Thence the deep water channel passed slightly to the westward of the
central line between the piers. This latter portion of the channel had
become exceedingly narrow by virtue of the sandbanks which had formed
on either side of it and which actually uncovered at low water. A
vessel drawing more than twelve feet or so was forced to keep exactly
in the middle of this dredged channel to avoid grounding. Photographs
taken at or near high tide gave the channel the appearance of extending
from one pier to the other, at least a distance of one hundred yards;
those taken near low water showed how narrow the channel really was.
In the region of the two piers the silting of the sand was more rapid
than elsewhere: the narrowest part of the channel was situated near the
shore ends of these piers.
[Sidenote: Defences on the Mole]
The Germans had not rested satisfied with either the Mole, the canal
entrance, or the lock as they found them. The Mole itself had been
transformed into a fortress, and further defences had been constructed
for the purpose of guarding the canal.
[Illustration: A PORTION OF THE GERMAN BATTERY ON THE LIGHTHOUSE
EXTENSION OF THE MOLE. VIEW OF THE CANAL ENTRANCE WITH ITS CURVED
PIERS. This photograph was taken at high tide. Note the Mole in the
distance]
Batteries were placed on both sides of the canal entrance. These
ranged from four-inch guns to {29} twelve-inch guns. Barbed wire
entanglements were erected along the shore line; trenches, containing
machine guns, were dug close behind them. It was believed that a boom
of some sort, capable of being hauled across the channel or removed at
will, was kept handy to the outer lock gate. The gate itself,
"caisson" is the correct technical term, was withdrawn into an armoured
housing, impervious to shells or bombs, when the lock was opened to
allow vessels to pass through. The caisson was also provided with an
armoured roof for defence against aerial bombs. The lights on the
wooden piers were only lit when specially required to guide a German
vessel to the entrance.
On the Mole a very large seaplane base was established with the
original passenger station as its principal building. Several other
buildings for housing seaplanes, fuel, or bombs, and workshops were
erected by the Germans close by. A merchant steamer, the _Brussels_,
formerly commanded by the ill-fated Captain Fryatt, whom the Germans
did to death so abominably, was moored alongside the station, and was
believed to be used as living quarters for the personnel of the
seaplane base.
The broad portion of the Mole was used as a base for submarines passing
through Zeebrugge _en route_ for Bruges or to the open sea; it was also
used for such torpedo craft and mine-sweepers as were required for
immediate duty in that locality. From the north-eastern large shed to
the lighthouse the Mole had been turned into a veritable fortress. It
was believed that the lighthouse was used as the Mole signal station.
A battery of six or seven guns was situated on {30} the lighthouse
extension of the Mole. These guns were at first surmised to be
3.5-inch guns, but it is probable that they were larger--in fact, up to
5.9-inch guns firing a shell of approximately one hundred pounds in
weight. It was believed that the guns of this battery could fire out
to sea and could be turned to fire towards the shore.
Any vessel approaching from seaward and passing into the dredged
channel, _en route_ to the canal, would be within the danger zone of
this battery, from the latter's extreme range out at sea to the canal
lock, always provided that the state of the visibility allowed the
vessel to be seen. Incidentally, owing to the situation of the deep
channel, the vessel would be obliged to pass within _a few yards_ of
this battery when rounding the Mole end. A vessel endeavouring to
berth alongside the outer wall would have to approach close to this
battery, i.e., on a westerly course. At first sight it might appear
feasible to approach _from_ the westward on an easterly course and thus
avoid passing close to the battery, but that is not so. High tide and
slack stream do not coincide on this coast. For about three hours on
each side of high tide the streams run _to_ the eastward: at other
states of the tide there would be insufficient depths of water for a
vessel to berth alongside. It would therefore be necessary to approach
from the eastward, i.e., to stem the tidal stream.
[Illustration: AERIAL PHOTOGRAPH OF THE CANAL ENTRANCE. Taken shortly
before the enterprise, showing the sandbanks narrowing the entrance
channel. At the top of the photograph a dredger at work indicates the
position of the approach channel]
Now let us imagine for a few moments a duel between this battery and a
warship within--say--one thousand yards. The reader probably knows
that such a distance nowadays comes within the definition of
"point-blank range"; i.e., a range at which a gun {31} practically
cannot miss a ship. Picture, then, an average-sized vessel of three
hundred feet in length. The guns could hardly miss her--in fact, the
gunners could select which particular portion of her should serve as
their target. The ship's guns would return the fire. The most
vulnerable portions of the battery ashore are the guns themselves. The
muzzle of each gun showing just above the wall would, as viewed from
the ship, cover barely one square foot in size. Now at golf we call it
a "fluke" when a golfer holes out from the tee although he has attained
his object. (I apologise for this to non-golfers.) Similarly, if the
ship's gun _hits_ the shore gun we should call it a "fluke," although
that is the object forming the target. And, as already implied, if the
shore gun _misses_ the ship, that also will be a "fluke." On the face
of it, it certainly does not look as if the ship would stand much
chance, even at a distance of one thousand yards. But how if she is
closer? If a thousand yards is point-blank range, how shall we
designate a hundred yards?
At the eastern end of the broad part of the Mole, and on its floor
level, the Germans had erected a battery of three heavy guns. These
were so placed that they could fire on any incoming vessel immediately
she rounded the lighthouse. Woe betide a vessel attempting to do so in
the face of such guns. The latter were probably of the 5.9-inch type.
Under water, immediately below this battery, we eventually found some
submerged torpedo tubes, but I am not aware as to whether they were
constructed before the blocking operation or not; their direction of
fire was similar to that of the guns above them.
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Close westward of these batteries of heavy guns and torpedoes, and
standing against the high outer wall, the Germans had constructed a
long shed of reënforced concrete; this shed provided the living space
for the personnel of the Mole garrison.
The total numbers of Germans on the Mole probably reached not less than
a thousand. Although this number may include the personnel of the
seaplane base yet they would all be available for the defence of the
Mole in case of an attack.
Slightly to the westward of the garrison's quarters, trenches had been
sunk in the floor of the Mole and surrounded by three complete sets of
barbed wire entanglements. It was believed that the usual accessories
of a coast fort--e.g., searchlights and range-finders, etc.--were
placed on the outer wall parapet, and that there would probably be some
small guns there also.
[Sidenote: The Booms and Torpedo Craft]
So much for the Mole itself. Across the channel the Germans had placed
booms. One of these, consisting of four Rhine barges, was moored
between the eastern end of the broad part of the Mole and a buoy
situated two hundred and seventy yards to the southward. These barges
were filled with stone, had nets slung beneath them, and were connected
together by wire hawsers. If a surface vessel attempted to pass
between the buoy and the Mole she would be brought up by this boom and
probably damaged by collision with one of the barges. If a submarine
attempted to dive underneath the barges she would be caught up in the
nets. The other boom consisted of entanglement nets moored between a
series of buoys to the southeastward of the barges. Any ship
attempting {33} to pass through them would probably have her propellers
entangled, with the result that her engines would be brought to a
complete stop. Thus, whichever boom was encountered by a ship, the
latter would, at the least, be partially disabled and stopped. The
Mole batteries could then have sunk her at their leisure by gunfire.
The only route by which a vessel could pass clear of these two booms
was that between the southeastern barge and the northern entanglement
net; i.e., within two hundred and fifty yards of the heavy gun battery
on the Mole. But even if, by dint of good fortune or special good
management, a vessel managed to pass the Mole batteries and the booms,
she would still have to run the gantlet of the naval vessels in the
anchorage and the batteries on shore before reaching the canal.
[Illustration: THE NORTHEASTERN END OF THE MOLE
a. The shadows of the parapet wall and of the lighthouse
at its extremity
b. The Mole batteries
c. Trench system surrounded by barbed wire
d. German torpedo craft alongside Mole
e. The barge boom
f. The boom of entanglement nets]
The German torpedo craft, which were available for local duty, used to
berth alongside the inner side of the Mole, close to the westward of
the barge boom. By virtue of their guns, torpedoes, and searchlights,
and the fact that they probably kept up steam in readiness for instant
action, these craft provided a valuable addition to the Mole and canal
defences.
The foregoing description of the local defences at Zeebrugge has
probably been sufficiently detailed to lead to the conclusion that the
Germans were fully alive to the possibility of attacks on the Mole or
canal. Whether or not they considered that such attacks would only
form part of some more ambitious operation, such as a military landing
on the coast, our enemies had left practically no stone unturned to
repel them. The defence measures must have {34} appeared, especially
to those on the spot, to be more than sufficient.
It is well known that, although the possession of detailed local
knowledge will usually be of great value towards the formation of plans
of attack, there are occasions when local knowledge is apt to make
local difficulties loom extremely large. For instance, in this
particular case, the navigational difficulties caused by the strong
tidal stream, the difficulty of recognising objects on the low-lying
shore during darkness, the uninviting appearance of the outer Mole wall
as an obstacle to be surmounted, and many other matters would probably
have induced the belief, in those who were actually acquainted with
these difficulties, that such attacks would have no chance of success.
There is, therefore, reason to believe that, although they realised an
attack might be attempted, the Germans were perfectly satisfied that
the defences could neither be improved nor penetrated.
The reader will probably have arrived at the conclusion that the
Germans were devilish in their thoroughness. Yet there was still one
joint left in their armour--and we penetrated it. But I must not
anticipate.
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