Read Ebook: The Blocking of Zeebrugge by Carpenter Alfred Francis Blakeney

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ates of the tide.

Mention has already been made that the only harbours on the coast eastward of Nieuport were situated at Ostende, Blankenberghe, and Zeebrugge. But these were not natural harbours. They had been artificially cut out of the coast-line by means of dredging. The entrance channels were preserved by piers built out into the sea and by dredging operations designed to retain the desired depths of water.

Ostende, before the war, had been much used as a commercial harbour, and was therefore provided with numerous wharves, basins, and docks. It was a suitable harbour for all classes of submarines and torpedo craft. Blankenberghe was a little harbour about nine miles east of Ostende and three miles west of Zeebrugge. Its depth was exceedingly small; it could, therefore, only be used for shallow draught vessels such as fishing boats, motor boats, and the like. It was true that the rise of tide, amounting to approximately fifteen feet, would enable larger vessels to enter or leave near the time of high water, but any naval vessel stationed in a harbour from which it can only proceed to sea during a limited portion of the twenty-four hours at once loses much of its value. Zeebrugge could accommodate vessels up to a considerable size: the harbour works and depths will be described in detail presently. Although these three places provided the only harbours on the coast, there was a harbour of great importance at Bruges, about eight miles inland from Zeebrugge.

Bruges harbour was also entirely artificial, consisting of locks, basins, and waterways built on the canal system. Bruges was connected to the sea by means of canals running to Zeebrugge and Ostende, these canals converging on the waterways of Bruges in such a manner that vessels of a certain limited size could pass from Ostende to Zeebrugge, and vice versa, without actually proceeding into the open sea. A series of small canals also connected Bruges to Antwerp, via Ghent, but this canal system, being only constructed to accommodate barges, did not materially add to the value of Bruges as a harbour for sea-going vessels.

Of the three canal systems connecting at Bruges, the canal to Zeebrugge easily held first place in importance. This canal was built by the Belgians. It was commenced in 1896 and completed in 1907. Six and a quarter miles in length, it was almost entirely straight throughout. It could accommodate torpedo-boat destroyers or submarines, both of the largest size, and could, if required, have been used by light cruisers.

At the seaward end of the Ostende and Zeebrugge canals, locks were constructed so that vessels could pass from the canals to the sea, or the reverse, at any state of the tide, without lowering the level of the water in the canal.

The above-mentioned harbours were used for naval purposes by Germany as follows. Bruges was chosen as the main naval base. Shelters for protecting submarines from aerial attack, floating docks, repair workshops, all the other facilities which go to make a modern dockyard for small vessels, and the necessary stores and ammunition, were to be found there. The number of naval craft based on Flanders appeared to vary considerably; but, at the beginning of 1918, approximately eighteen submarines and twenty-five destroyers or torpedo-boats would be at Bruges on an average day. The submarines lay in the special shelters which were covered by roofs of re?nforced concrete several feet in thickness. Bruges, then, was not only the dockyard but also the resting-place of practically all the German naval craft based on Flanders.

The sea exits from Bruges, as already mentioned, were situated at Ostende and Zeebrugge. There was some doubt, however, whether the Bruges-Ostende canal could be used for the passage of anything larger than very shallow draught vessels such as motor boats or barges. The Ostende canal was known to be narrow, tortuous, and shallow; it had been constructed many years earlier than the Zeebrugge canal.

At Zeebrugge and Ostende a few German craft were usually stationed for duties of an immediate nature such as mine-sweeping, patrolling, and duties connected with the defence of the coast. These harbours were specially useful as taking-off places for vessels which had concentrated in readiness for operations at sea, or as bolt-holes for the same craft when pursued by our patrol vessels. Both harbours were open to bombardment from the sea; that reason, more than any other, probably influenced the Germans to use Bruges for their main base. Ostende, being more open to attack from the sea and air than was Zeebrugge, was the less important harbour of the two.

Blankenberghe harbour, owing to its small size and shallow depth, was used as a base for the German armed motor boats; it is believed that about thirty were stationed there. This harbour, being unconnected with the canal system, was not in direct inland communication with Bruges by water.

In addition to the submarines and torpedo craft already mentioned, the Germans had a large number of trawlers based on the various harbours for mine-sweeping and patrol duties. At Zeebrugge they had their largest seaplane base in Flanders; another seaplane base was situated at Ostende.

In due course Flanders had become a veritable hornet's nest. Let us consider for a few moments to what extent these hornets could trouble us.

All these vessels were continually open to attack, not only from submarines but also from the surface craft and aircraft based in Flanders. At any chosen moment, preferably at night or during misty days, these hornets could emanate from Ostende or Zeebrugge on their deadly missions. Further westward our trans-Atlantic lines of communication offered innumerable opportunities for the German submarine commanders to display their brutality against comparatively defenceless merchant vessels, or to attack transports carrying munitions of war and troops from the American Continent. The passage through the English Channel afforded the most direct route for German submarines proceeding to, or returning from, their hunting-grounds.

The mercantile traffic off the southeast coast of England and in the entrance to the Thames was also within easy reach of the German bases in Flanders; so were our seaside resorts, such as Ramsgate and Margate, which provided favourable opportunities for bombardments with resultant casualty lists of innocent women and children.

Dunkerque and Calais on the French coast were the nearest seaport objectives to the Flanders coast; they both experienced frequent aerial attacks and an occasional bombardment from the sea.

A point which, until recently, unaccountably seemed to have escaped notice was that the work of the Dover Patrol was carried out on behalf of all the Allies and of the United States. It was not a British force acting solely in British interests. Though it is difficult, and perhaps invidious, to apportion the credit for protecting the Allied lines of communication, yet there is no shadow of doubt that the troops from Canada and from the United States of America owed to the Dover Patrol force a tremendous debt of gratitude for their safe passage overseas. Recognition of this fact has since been shown by the erection at New York, and on the French coast, of memorials to the Dover Patrol. When the late war has faded into history, and those of us who took part have long since "gone west," such memorials will remain to bear witness to the splendid sacrifice and unselfish gallantry of those hardy seamen who did their utmost to uphold the honour of civilisation and to destroy the forces working for its overthrow.

The final closing of the Straits, however, was far from accomplished by the spring of 1918. At that time we had reason to believe that a large percentage of the total Allied losses in merchant ships was caused by the Flanders submarines, and that the percentage was on the increase.

Whatever suggestions were made, it is clear that there could be only two radical methods of attaining our object. The most satisfactory, of course, would have been the recapture of the Flanders coast and of Bruges, with all the hornets in their nests, by means of military operations. Unfortunately that was impracticable; the Allied armies were not yet sufficiently strong. The only alternative to capture of the craft in their harbours was that of preventing them putting to sea--i.e., destroying or blocking their exits. Several schemes for blocking operations had been proposed. In tactical method they had varied from blowing up the harbour entrances, as suggested by the Halifax disaster, to "building in" the entrances under cover of poison gas. Whether such methods were considered too risky, too expensive, or too hopelessly fantastic is more than the author of this book knows.

An attack on Zeebrugge had been strongly advocated by an eminent flag officer in November, 1916, but no details were given by him as to the nature of the operation. In May, 1917, detailed proposals for an attack had been submitted to the Admiralty by another distinguished officer. This attack involved a landing on the Mole at Zeebrugge, the general idea of which was not dissimilar from that eventually followed. This particular scheme had not earned the approval of Their Lordships, nor was it considered suitable by the Vice-Admiral then in command at Dover.

Many months after the blocking of Zeebrugge had become an accomplished fact two earlier schemes came to light--these having emanated from the author of that submitted in May, 1917. In November, 1917, however, the only previous proposals which were available for consideration by the Planning Division of the Staff were those of November, 1916, and May, 1917, mentioned above.

In November, 1917, Admiral Sir John Jellicoe was First Sea Lord and Chief of the Naval Staff. He had requested the Director of Plans to consider, amongst many other things, the possibility of blocking the Belgian ports.

The foregoing definite fact has been purposely inserted to correct other statements which have been published elsewhere, presumably in error. I shall deal with the details of the Plan in a subsequent chapter.

Before we pass on to review the difficulties of blocking the exits from the German bases it would be advisable to consider the probable effects of such an operation; this being the logical sequence actually followed before the details of the Plan were formulated.

The results to be attained by blocking the exits would probably be as follows. Firstly, there would be a reduction in the number of Allied vessels sunk by mine or submarine warfare; secondly, a decrease in raid activity on the part of the enemy torpedo craft; thirdly, the loss of a convenient advanced base for small craft operating in conjunction with certain movements of the High Seas Fleet; and, fourthly, the reduction in the number of enemy vessels available for the purposes mentioned.

The first two results concerned reduction of enemy activity arising from the longer passages involved by the use of more distant bases such as Heligoland or the German rivers from which the small craft could continue their depredations. The third result speaks for itself. With regard to the fourth, it has already been stated that, on an average day, there would be many torpedo craft or submarines resting and repairing at Bruges. If the exits were blocked the use of these craft would be denied to the enemy, just as effectually as if they were sunk, for as long as the exits remained unopened. This loss to the enemy, temporary or permanent, could doubtless be described in terms of reduction of Allied losses of merchant tonnage. The Admiralty authorities could probably have calculated, within fairly correct estimates, the average loss of merchant tonnage caused to the Allies by a single enemy submarine or surface torpedo craft. Our former average loss per given period would thus be lessened in proportion to the number of enemy vessels bottled up in the canals during that period.

There would, of course, be other, less important, consequences arising from the blocking of these exits; e.g., the inconveniences caused by the necessary transfer of fuelling and repair facilities elsewhere, the extra work thrown on the escorting vessels in the Bight, and the fact that the craft already at sea and operating from the Flanders coast would be forced to curtail their current trips if they desired to arrive at their new bases with their usual reserves of fuel.

All these material gains to the Allies would be of considerable importance, but the moral effect was not unworthy of consideration. The more audacious an undertaking against an enemy the more intense will be the victor's enthusiasm consequent on success, and the greater the despondency and loss of moral to the vanquished. Attempts to block a hostile port in the face of carefully prepared defence measures may certainly be described as audacious, unless the word "impertinent," which the author is inclined to allocate to this particular event, is deemed to be more truly descriptive. If we endeavour to imagine what our own feelings would be on hearing that enemy vessels had entered one of our strongly defended harbours and blocked the entrance, we shall arrive at some idea as to the probable moral effect produced by such an enterprise. In spite of the almost entire absence of activity on the part of the High Seas Fleet, the Germans had never ceased to sing its praises with all the bombast of which their waning spirit was capable. It was not difficult, therefore, to estimate the dejection and consternation that would spread throughout Germany when the success of our efforts became known. The loss of prestige in the German Navy would be not merely certain but perhaps of vital consequence later on.

THE LOCAL SITUATION. THE LOCAL DEFENCES.

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.

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 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 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.

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.

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.

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 re?nforced 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.

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.

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