CHAPTER II
THE LOCAL SITUATION. THE LOCAL DEFENCES.
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.
PORT OF ZEEBRUGGE
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 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.
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 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."
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.
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.
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 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.
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.
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 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 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.
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 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.
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.
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 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.
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 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.