Neither Zeebrugge, Ostend, nor Bruges could be rendered untenable to the enemy with the guns available during 1917, although Ostend in particular, and Zeebrugge to a lesser extent, could be, and were frequently, brought under fire when certain conditions prevailed, and some temporary damage caused. Indeed, the fire against Ostend was so effective that the harbour fell into disuse as a base towards the end of 1917. We were arranging also in 1917 for mounting naval guns on sh.o.r.e that would bring Bruges under fire, after the enemy had been driven from Ostend by the contemplated operation which is mentioned later. When forced to abandon this operation, in consequence of the military advance being held up by the weather, these guns were mounted in monitors.
In the matter of blocking the entrance to the ports of Zeebrugge and Ostend, the fact had to be recognized that effective permanent blocking operations against destroyers and submarines were not practicable, mainly because of the great rise and fall above low water at ordinary spring tides, which is 14 feet at Ostend and 13 feet at Zeebrugge for about half the days in each month. Low water at Ostend also lasts for one hour. Therefore, even if block-ships were sunk in the most favourable position the operation of making a pa.s.sage by cutting away the upper works of the block-ships was not a difficult matter, and the Germans are a painstaking people. This pa.s.sage could be used for some time on each side of high water by vessels like destroyers drawing less than 14 feet, or submarines drawing, say, 14 feet. The block would, therefore, be of a temporary and not a permanent nature, although it would undoubtedly be a source of considerable inconvenience. At the same time it was realized that, although permanent blocking was not practicable, a temporary block would be of use, and that the moral effect alone of such an operation would be of great value. These considerations, together with the abandonment of the proposed landing on the Belgian coast, owing to unfavourable military conditions, led to the decision late in 1917 to undertake blocking operations concurrently with an attack on the vessels alongside the Mole at Zeebrugge.
In order to carry out the general policy mentioned, the eastern end of the Straits of Dover had been heavily mined at intervals during the war, and these mines had proved to be a sufficient deterrent against any attempt on the part of surface vessels larger than destroyers to pa.s.s through. Owing to the rise of tide enemy destroyers could pa.s.s over the minefields at high water without risk of injury, and they frequently did so pa.s.s. Many attempts had been made to prevent the pa.s.sage of enemy submarines by means of obstructions, but without much success; and at the end of 1916 a "mine net barrage"-i.e. a series of wire nets of wide mesh carrying mines-was in process of being placed by us right across the Straits from the South Goodwin Buoy to the West Dyck Bank, a length of 28 miles, it being arranged that the French would continue the barrage from this position to the French coast. The construction of the barrage was much delayed by the difficulty in procuring mooring buoys, and it was not completed until the late summer of 1917. Even then it was not an effective barrier owing to the tidal effects, as submarines were able to pa.s.s over it during strong tides, or to dive under the nets as an alternative; it was not practicable to use nets more than 60 feet deep, whilst the depth of water in places exceeded 120 feet.
Deep mines were laid to guard the water below the net, but although these were moored at some considerable distance from the barrage, trouble was experienced owing to the mines dragging their moorings in the strong tide-way and fouling the nets. One series had to be entirely swept up for this reason. Many devices were tried with the object of improving this barrage, and many clever brains were at work on it. And all the time our drifters with their crews of gallant fishermen, with Captain Bird at their head, worked day after day at the task of keeping the nets efficient.
In spite of its deficiencies the barrage was believed to be responsible for the destruction of a few submarines, and it did certainly render the pa.s.sage of the Straits more difficult, and therefore its moral effect was appreciable. Towards the end of 1917, however, evidence came into our possession showing that more submarines were actually pa.s.sing the Straits of Dover than had been believed to be the case, and it became a question whether a proportion of the drifters, etc., required for the maintenance of the nets of the barrage should be utilized instead for patrol work in the vicinity of the mine barrage then being laid between Folkestone and Cape Grisnez. This action was taken, drifters being gradually moved to the new area.
In April, 1916, a net barrage, with lines of deep mines on the Belgian side of the nets, had also been laid along the Belgian coast covering the exits from the ports of Ostend and Zeebrugge as well as the coast between those ports. These nets were laid at a distance of some 24,000 yards from the sh.o.r.e. This plan had proved most successful in preventing minelaying by submarines in the Straits of Dover, and the barrage was maintained from May to October, but the weather conditions had prevented its continuance from that date.
The operation was repeated in 1917, the barrage being kept in position until December, when the question of withdrawing the craft required for its maintenance for patrol work in connection with the minefield laid on the Folkestone-Grisnez line came under discussion.
The Belgian coast barrage being in the nature of a surprise was probably more useful as a deterrent to submarine activity in 1916 than in 1917. In both years a strong patrol of monitors, destroyers, minesweepers, drifters for net repairs, and other vessels was maintained in position to the westward of the barrage to prevent interference with the nets by enemy vessels and to keep them effective.
These vessels were patrolling daily within 13 or 14 sea miles of the two enemy destroyer and submarine bases, and although occasionally attacked, were not driven off in spite of the superior destroyer force which the enemy could always bring to bear. In 1917 actions between our vessels and those of the enemy, and between our own and enemy aircraft, were of very frequent occurrence. The Germans also introduced a new weapon in the form of fast motor boats controlled by a cable from the sh.o.r.e and guided by signals from aircraft, these boats being heavily loaded in the fore part with explosives which detonated on contact with any vessels attacked. On only one occasion in four attacks were the boats successful in hitting their mark, and the monitor Terror, which was struck in this instance, although considerably damaged in her bulge protection, was successfully brought back to port and repaired.
Whilst our monitors were on patrol near the barrage, as well as on other occasions, every favourable opportunity was taken of bombarding the bases at Zeebrugge and Ostend. In the former case the targets fired at were the lock gates, and in the latter the workshops, to which considerable damage was frequently occasioned, as well as to vessels lying in the basin.
These bombardments were carried out in 1917 at distances exceeding 25,000 yards. The long range was necessary on account of the net barrage, and also because of the rapidity with which the "Knocke" and "Tirpitz" sh.o.r.e batteries obtained the range of monitors attacking them, one hit on an unprotected monitor being sufficient to sink her.
They were also invariably carried out under the protection of a smoke screen; in the autumn of 1917 the enemy commenced to start a smoke screen himself as soon as we opened fire, thus interfering with our observation of fire even from aircraft, but in spite of this much damage resulted from the bombardments. Our observation of fire being necessarily carried out by aircraft, and the enemy attempting similar measures in his return gunfire, resulted in aerial combats over the monitors being a frequent occurrence.
The carefully organized arrangements made by Admiral Bacon for these coastal bombardments excited my warm admiration. He left nothing to chance, and everything that ingenuity could devise and patient preparation could a.s.sist was done to ensure success. He received a.s.sistance from a staff which, though small in number, was imbued with his own spirit, and he brought to great perfection and achieved wonderful success in methods of warfare of which the Navy had had no previous experience.
During the year 1917 aerial bombing attacks were persistently carried out on the German naval bases in Belgium by the Royal Naval Air Force at Dunkirk, which came within the sphere of the Dover Command. These attacks had as their main object the destruction of enemy vessels lying in these bases, and of the means for their maintenance and repair. The attacks, under the very skilful direction of Captain Lambe, R.N., were as incessant as our resources and the weather admitted, and our gallant and splendidly efficient airmen of the R.N.A.S. were veritable thorns in the sides of the Germans. Our bombing machines as well as our fighting aircraft were often required to attack military instead of naval objectives, and several squadrons of our fighting machines were lent to the military for the operations carried out during the year on the Western Front; they did most excellent work, and earned the high commendation of Sir Douglas Haig (now Earl Haig). But we were still able to work against naval objectives. Zeebrugge, for instance, was bombed on seven nights during April and five nights during May, and during September a total weight of 86 tons of bombs was dropped on enemy objectives by the Dunkirk Naval aircraft, and we had good reason to be satisfied with the results achieved. During this same month 18 enemy aircraft were destroyed and 43 driven down. Attacks upon enemy aerodromes were very frequent, and this form of aerial offensive undoubtedly exercised a very deterrent influence upon enemy aerial activity over England. Two submarines also were attacked and were thought to be destroyed, all by our machines from Dunkirk. To Commodore G.o.dfrey Paine, the Fifth Sea Lord at the Admiralty, who was in charge of the R.N.A.S., and to the staff a.s.sisting him our thanks were due for the great work they accomplished in developing new and efficient types of machines and in overcoming so far as was possible the difficulties of supply. The amount of bombing work carried out in 1917 cannot, of course, compare with that accomplished during 1918, when production had got into its stride and the number of machines available was consequently so very much larger.
Whether it was due to our aerial attacks on Bruges that the German destroyers in the autumn months frequently left that base and lay at Zeebrugge cannot be known, but they did so, and as soon as we discovered this fact by aerial photographs, plans were laid by Sir Reginald Bacon for a combined naval and aerial night operation. The idea was for the aircraft to bomb Zeebrugge heavily in the vicinity of the Mole, as we ascertained by trial that on such occasions the enemy"s destroyers left the Mole and proceeded outside the harbour. There we had our coastal motor boats lying off waiting for the destroyers to come out, and on the first occasion that the operation was carried out one German destroyer was sunk and another believed to have been damaged, if not also sunk, by torpedoes fired by the coastal motor boats, to which very great credit is due for their work, not only on this, but on many other occasions; these boats were manned by a very gallant and enterprising personnel.
Numerous other operations against enemy destroyers, torpedo boats and submarines were carried out during the year, as recounted in Sir Reginald Bacon"s book, and in the autumn, when supplies of the new pattern mines were becoming available, some minelaying destroyers were sent to Dover; these vessels, as well as coastal motor boats and motor launches, were continually laying mines in the vicinity of Zeebrugge and Ostend with excellent results, a considerable number of German destroyers and torpedo boats working from Zeebrugge being known to have been mined, and a fair proportion of them sunk by these measures.
In addition to the operations carried out in the vicinity of the Belgian coast, the Dover force constantly laid traps for the enemy destroyers and submarines in waters through which they were known to pa.s.s.
Lines of mined nets laid across the expected track of enemy vessels was a device frequently employed; submarines, as has been stated, were used on the cross-Channel barrage to watch for the pa.s.sage of enemy submarines and destroyers, and everything that ingenuity could suggest was done to catch the German craft if they came out.
Such measures were supplementary to the work of the destroyers engaged on the regular Dover Patrol, the indomitable Sixth Flotilla.
A great deal depended upon the work of these destroyers. They formed the princ.i.p.al, indeed practically the only, protection for the vast volume of trade pa.s.sing the Straits of Dover as well as for our cross-Channel communications. When the nearness of Zeebrugge and Ostend to Dover is considered (a matter of only 72 and 62 miles respectively), and the fact that one and sometimes two German flotillas, each comprising eleven large and heavily armed torpedo-boat destroyers, were usually based on Bruges, together with a force of large modern torpedo boats and a very considerable number of submarines, it will be realized that the position was ever one of considerable anxiety. It was further always possible for the enemy to send reinforcements of additional flotillas from German ports, or to send heavier craft with minesweepers to sweep a clear channel, timing their arrival to coincide with an intended attack, and thus to place the German forces in a position of overwhelming superiority.
Our own Dover force at the commencement of 1917 consisted of one light cruiser, three flotilla leaders, eighteen modern destroyers, including several of the old "Tribal" cla.s.s, eleven old destroyers of the 30-knot cla.s.s (the latter being unfit to engage the German destroyers), and five "P" boats. Of this total the average number not available at any moment may be taken as at least one-third. This may seem a high estimate, but in addition to the ordinary refits and the time required for boiler cleaning, the vessels of the Dover Patrol working in very dangerous, foggy and narrow waters suffered heavy casualties from mines and collisions. The work of the Dover force included the duty of escorting the heavy traffic between Dover and Folkestone and the French ports, this being mostly carried on during daylight hours owing to the prevalence of submarine-laid mines and the necessity for sweeping the various channels before the traffic-which included a very large troop traffic-was allowed to cross. An average of more than twenty transports and hospital ships crossed the Straits daily during 1917, irrespective of other vessels. The destroyers which were engaged during daylight hours in this work, and those patrolling the barrages across the Straits and off the Belgian coast, obviously required some rest at night, and this fact reduced the number available for duty in the dark hours, the only time during which enemy destroyer attacks took place.
Up to the spring of 1917 the examination service of all vessels pa.s.sing the Straits of Dover had been carried out in the Downs. This led to a very large number of merchant ships being at anchor in the Downs at night, and these vessels were obviously open to attack by enemy craft of every description. It was always a marvel to me that the enemy showed such a lack of enterprise in failing to take advantage of these conditions. In order to protect these vessels to some extent, a light cruiser from Dover, and one usually borrowed from Harwich, together with a division of destroyers either from Dover, or borrowed also from Harwich, were anch.o.r.ed off Ramsgate, and backed by a monitor if one was available, necessitating a division of strength and a weakening of the force available for work in the Straits of Dover proper.
The result of this conflict of interests in the early part of the year was that for the patrol of the actual Straits in the darkness of night on a line some 30 miles in length, the number of vessels available rarely if ever exceeded six-viz. two flotilla leaders and four destroyers, with the destroyers resting in Dover (four to six in number) with steam ready at short notice as a reserve.
An attack had been made on the Dover Patrol in October, 1916, which had resulted in the loss by us of one destroyer and six drifters, and serious damage to another destroyer. A consideration of the circ.u.mstances of this attack after my arrival at the Admiralty led me to discuss with Sir Reginald Bacon the question of keeping such forces as we had in the Straits at night concentrated as far as possible. This disposition naturally increased the risk of enemy vessels pa.s.sing un.o.bserved, but ensured that they would be encountered in greater, although not equal, force if sighted.
Steps were also taken to reduce the tempting bait represented by the presence of so many merchant ships in the Downs at night. Sir Reginald Bacon proposed that the portion of the examination service which dealt with south-going ships should be moved to Southend, and the transfer was effected as rapidly as possible and without difficulty, thereby a.s.sisting to free us from a source of anxiety.
During the early part of 1917 the enemy carried out a few destroyer raids both on English coast towns in the vicinity of Dover and the French ports of Dunkirk and Calais. As a result of these raids, which, though regrettable, were of no military importance, a good deal of ill-informed criticism was levelled at the Admiralty and the Vice-Admiral commanding at Dover. To anyone conversant with the conditions, the wonder was not that the raids took place, but that the enemy showed so little enterprise in carrying out-with the great advantages he possessed-operations of real, if not vital, military value.
The only explanation is that he foresaw the moral effect that his tip-and-run raids would produce; and he considered that the effect of the resulting agitation might be of no inconsiderable value to himself; the actual damage done was almost negligible, apart from the loss of some eight lives, which we all deplored. It is perhaps natural that people who have never experienced war at close quarters should be impatient if its consequences are brought home to them. A visit to Dunkirk would have shown what war really meant, and the bearing of the inhabitants of that town would have taught a valuable lesson.
The conditions in the Straits have already been mentioned, but too much emphasis cannot be laid on them. The enemy who possessed the incalculable advantage of the initiative, had at his disposal, whenever he took heart to plan an attack, a force of at least twenty-two very good destroyers, all unfortunately of higher speed than anything we could bring against them, and more heavily armed than many of our destroyers. This force was based within seventy miles of Dover, and as the Germans had no traffic of any sort to defend, was always available for offensive operations against our up and down or cross-Channel traffic. Our Dover force was inferior even at full strength, but owing to the inevitable absence of vessels under repair or refitting and the manifold duties imposed upon it, was bound to be in a position of marked inferiority in any night attack undertaken by the Germans against any objective in the Straits.
The enemy had a great choice of objectives. These were: first, the traffic in the Channel or the destroyers watching the Straits (the most important military objective); second, the merchant ships anch.o.r.ed in the Downs; third, the British monitors anch.o.r.ed off Dunkirk; fourth, the French ports, Dunkirk, Boulogne and Calais, and the British port of Dover; and fifth, the British undefended towns of Ramsgate, Margate, Lowestoft, etc., which German mentality did not hesitate to attack.
A glance at Chart F [Transcriber"s note: Not preserved in book.] will show how widely separated are these objectives and how impossible it was for the small Dover force to defend them all simultaneously, especially during the hours of darkness. Any such attempt would have led to a dispersion of force which would have been criminal. The distance from Dunkirk along the French coast to Calais, thence to Dover and along the English coast to the North Foreland is 60 miles. The distance at which an enemy destroyer can be seen at night is about a quarter of a mile, and the enemy could select any point of the 60 miles for attack, or could vary the scene of operations by bombarding Lowestoft or towns in the vicinity, which were only 80 miles from Zeebrugge and equally vulnerable to attack, since the enemy"s destroyers could leave their base before dark, carry out their hurried bombardment, and return before daylight. In whatever quarter he attacked he could be certain of great local superiority of force, although, of course, he knew full well that the first sign of an attack would be a signal to our forces to try to cut him off from his bases. Therein lay the reason for the tip-and-run nature of the raids, which lasted for a few minutes only. The enemy realized that we should endeavour to intercept his force as soon as it had disclosed its presence. The Germans had naturally to take the risk of encountering our vessels on the way to his objectives, but at night this risk was but slight.
As it was obviously impossible to prevent bombardments by stationing destroyers in adequate force for the protection of each town, the only possible alternative, unless such bombardments were ignored, was to give the most vulnerable points protection by artillery mounted on sh.o.r.e. This was a War Office, not an Admiralty, responsibility; but as the War Office had not the means available, the Admiralty decided to take the matter in hand, and in the spring of 1917 some 6-inch naval guns taken from our reserves were mounted in the vicinity of the North Foreland. Further, an old monitor, which was of no use for other work owing to her machinery being unfit, was moored to the southward of Ramsgate, and her guns commanded the Downs. Searchlights were also mounted on sh.o.r.e, but more reliance was placed on the use of star sh.e.l.ls, of which the earliest supplies were sent to these guns. The result was immediately apparent. German destroyers appeared one night later on off the North Foreland and opened fire, which was returned by the monitor and the sh.o.r.e guns. The enemy immediately withdrew, and never appeared again in 1917 in this neighbourhood.
Meanwhile efforts had been made to increase the strength of the Dover force, and by the end of June it stood at 4 flotilla leaders, 29 modern destroyers (including "Tribal" cla.s.s), 10 old 30-knotters, and 6 "P" boats. The increase in strength was rendered possible owing to the relief of destroyers of the "M" and "L" cla.s.ses at Harwich by new vessels recently completed and by the weakening of that force numerically. The flotilla leaders were a great a.s.set to Dover, as, although they were coal-burning ships and lacked the speed of the German destroyers, their powerful armament made it possible for them to engage successfully a numerically greatly superior force. This was clearly shown on the occasion of the action between the Broke and Swift and a German force of destroyers on the night of April 20-21, 1917.
The flotilla leaders on that occasion were, as was customary, patrolling at the Dover end of the cross-Channel barrage. The enemy"s destroyers were in two detachments. One detachment, consisting apparently of four boats, pa.s.sed, it was thought, round the western end of the barrage at high tide close to the South Goodwin Buoy, and fired a few rounds at Dover. The other detachment of two boats went towards Calais, and the whole force seems to have met at a rendezvous prior to its return to its base.
The Broke and Swift intercepted them on their return, and after a hot engagement succeeded in sinking two of the enemy vessels, one being very neatly rammed by the Broke (Captain E.R.G.R. Evans, C.B.), and the second sunk by torpedoes. Some of the remaining four boats undoubtedly suffered serious damage. Our flotilla leaders were handled with conspicuous skill, and the enemy was taught a lesson which resulted in his displaying even greater caution in laying his plans and evincing a greater respect for the Dover force for many months.
The success of the Broke and Swift was received with a chorus of praise, and this praise was undoubtedly most fully deserved, but once again an example was furnished of the manner in which public attention becomes riveted upon the dramatic moments of naval warfare whilst the long and patient labour by which the dramatic moments are brought about is ignored.
Thus in this case, but little attention was drawn to the years of arduous work performed by the Sixth Flotilla in the Straits of Dover by day and by night, in dense fogs, heavy gales and blinding snowstorms, in waters which were constantly mined, and in the face of an enemy who was bound to be in greatly superior force whenever he chose to attack.
Little thought was given either to the wonderful and most gallant work carried out by the drifters of the Patrol, manned largely by fishermen, and practically defenceless against attack by the German destroyers.
The careful organization which conduced to the successful action was forgotten. Sir Reginald Bacon has told the story of all this work in his book, and I need not repeat it. But let it be added that victory depends less on such enheartening incidents, welcome as they are, than on the patient and usually monotonous performance of duty at sea by day and by night in all weathers, and on the skill in organization of the staff ash.o.r.e in foreseeing and forestalling enemy activity on a hundred and one occasions of which the public necessarily knows nothing.
It has been stated that reliable information reached us in the autumn of 1917 that enemy submarines were pa.s.sing the Straits of Dover in much greater numbers than we had hitherto believed to be the case, and the inefficiency of the net barrage in preventing the pa.s.sage was apparent.
Early in the year (in February) Sir Reginald Bacon had put forward a proposal for a deep minefield on the line Folkestone-Cape Grisnez, but confined only to the portion of the line to the southward of the Varne Shoal.
It was known that enemy submarines as a rule made this portion of their pa.s.sage submerged, and the minefield was designed to catch them.
The proposal was approved after personal discussion with Admiral Bacon, and directions were given that the earliest supplies of the new pattern mines were to be allocated for this service; these mines commenced to become available early in the following November, and were immediately laid.
Admiral Bacon suggested later the extension of the minefield to the westward of the Varne Shoal, so as to make it a complete barrier across the Channel. This was also approved and measures were taken to provide the necessary mines.
The question of illuminating at night the area covered by the deep minefield was also discussed at length with Sir Reginald Bacon. Various proposals were considered, such as the use of searchlights on Cape Grisnez and at Folkestone, together with the provision of small light-ships fitted with searchlights and moored at intervals across the Channel, and also the use of flares from patrol craft. Flares had already been experimented with from kite balloons by the Anti-Submarine Division of the War Staff, and they were found on trial to be efficient when used from drifters, and of great use in illuminating the patrol area so that the patrol craft might have better opportunities for sighting submarines and the latter be forced to dive into the minefields.
A committee had been meanwhile appointed by the First Lord to consider the question of the Dover Barrage in the light of the information we then possessed as to the pa.s.sage of enemy submarines through the Straits of Dover. This committee visited Dover on several occasions, and its members, some of whom were naval officers and some civilian engineers, were shown the existing arrangements.
The committee, which considered at first the question of providing an obstruction, ended by reporting that the existing barrage was inefficient (a fact which had become apparent), and made proposals for the establishment of the already approved minefield on the Folkestone-Grisnez line. I do not recollect that any definite new ideas were evolved as the outcome of the labours of this committee; some ideas regarding the details of the minefield, particularly as to the best form of obstruction that would catch submarines or other vessels on the surface, were put forward, as also some proposals for erecting towers in certain positions in the Straits. I do not think that these latter ever matured. The manner in which the minefield should be illuminated at night was discussed by the committee, and arrangements were made for the provision of the vessels proposed by Admiral Bacon.
Some disagreement arose on the subject of the provision of the necessary number of vessels for patrolling the minefield with a view to forcing the submarines to dive. In my view a question of this nature was one to be left in the hands of the Vice-Admiral at Dover, with experience on the spot, after I had emphasized to him the extreme importance attached to the provision of an ample number of patrol craft at the earliest possible moment. Interference by the Admiralty in such a detail of a flag officer"s command would in my opinion have been dangerous and incorrect, for so long as a flag officer retains the confidence of the Board he must be left to work his command in the manner considered best by him after having been informed of the approved general policy, since he is bound to be acquainted with the local situation to a far greater extent than any officer serving at the Admiralty or elsewhere. I discussed the matter personally with Sir Reginald Bacon, and was satisfied that he was aware of the views held by me and of the necessity for providing the patrol craft even at the expense of other services, as soon as he could make the requisite arrangements.
Sir Reginald Bacon"s three years" experience at Dover was a great a.s.set in dealing with this matter, as with other questions connected with the Command, more especially the difficult and embarra.s.sing operations on the Belgian coast. His ingenuity, originality, patience, power of organization and his methodical preparations for carrying out operations were always a great factor in ensuring success. These qualities were never shown more clearly than during the preparations made for landing a force of some 14,000 officers and men with tanks, artillery and transport on the coast of Belgium under the very muzzles of the German heavy coast artillery. It was estimated that the whole force would be put on sh.o.r.e in a period of twenty minutes. The scheme is described in full in Chapter IX. of the first volume of Sir Reginald Bacon"s book on the Dover Patrol. He had put the proposal before Admiral Sir Henry Jackson, my predecessor, who had expressed his concurrence so far as the naval portion of the scheme was concerned, and provided that the army made the necessary advance in Flanders. When the scheme was shown to me shortly after taking office as First Sea Lord I confess that I had some doubts as to the possibility of manoeuvring two monitors, with a pontoon 550 feet in length secured ahead of and between the bows of the monitors, but in view of the immense importance of driving the Germans from the Belgian coast and the fact that this scheme, if practicable, promised to facilitate greatly such an operation, approval was given for the construction of a pontoon, and after witnessing the first trials of the pontoon secured between two monitors which were themselves lashed together, I became convinced that this part of the operation was perfectly feasible. The remaining pontoons were therefore constructed, and preparations commenced in the greatest secrecy for the whole operation.
The next matter for trial was the arrangement devised by Sir R. Bacon for making it possible for tanks to mount the sea wall. These trials were carried out with great secrecy against a model of the sea wall built at the Headquarters of the Tank Corps in France, and were quite successful. It was necessary to see actual photographs of the tanks mounting the coping at the top of the sea wall to be convinced of the practicability of the scheme. A matter of great importance was the necessity for obtaining accurate information of the slope of the beach at the projected landing places in order that the practicability of grounding the pontoon could be ascertained. This information Sir R. Bacon, with his characteristic patience and ingenuity, obtained by means of aerial photographs taken at various states of tide.
Finally, to gain exact knowledge of the rise and fall of the tide, Admiral Bacon employed a submarine which submerged in the vicinity of Nieuport and registered the height of water above her hull for a period of twenty-four hours under conditions of spring and neap tides.