Practically all these types of mines required different treatment from the minesweepers. The Germans knew this and they cunningly mixed them all up. Moreover, they also sowed all sorts of anti-sweeping devices, carefully devised to put the sweeping gear of the minesweepers out of action—usually just before they passed over a particularly unhealthy patch of mines.
The men of the minesweepers, with their irrepressible humour, used to speak of their ships “being de-bagged” when they were robbed of their sweeping gear by one or other of the German devices, and this “de-bagging” of the ships proved to be one of their major troubles. Not only did it demand constant work in repairing the sweeping gear, but it made prodigious demands upon the supply organisation for replacements. Fortunately neither the supply organisation nor the endurance of the minesweepers’ crews proved unequal to the great demands made upon them.
As an instance of the trouble caused by the German anti-sweeping devices one may quote the experience of the 14th Minesweeping Flotilla, commanded by Commander J. W. A. Irvine, RNR, in HMS Romney. On D plus 2 this flotilla encountered a great many of these anti-sweeping devices. Eleven mines were swept and no less than 25 anti-sweeping devices were encountered. Seven of these “de-bagged” sweepers but—a great triumph—one of the German anti-sweeping devices was recovered intact and sent to the Admiralty for investigation.
The small minesweepers working close inshore had yet another problem with which to contend. This was due to the amount of wreckage and other flotsam off the beaches, which was apt to damage the screws of the small shallow-draught BYM’s. This problem did not, however, become really acute until after the great gale of D plus 13 to D plus 16. After that gale Lieutenant-Commander J. H. Butler, RNVR, commanding the 165th Minesweeping Flotilla, composed of BYM’s, reported that six of his ten ships had damaged screws owing to drifting wreckage and ropes’ ends. It was, nevertheless, a very real problem for these little minesweepers from D-day onwards. Later on, the flotsam in and around the anchorages became a nuisance and a danger on a different count—because it was so apt to be confused with the large numbers of novel and ingenious German decoys and booby traps dropped in the area or floated down by the tide in order to confuse the defences and create general “alarm and despondency.”
In order to deal with the menace Captain A. F. Pugsley, who was Captain of Patrols guarding the anchorages, instituting “scavenging days,” on which every craft under his command had to hoist every two hours flags denoting the number of bits of wreckage and flotsam recovered. Captain Pugsley rewarded the winning craft at the end of the “scavenging day” with an issue of “Mars bars”—a chocolate confection very popular with the sailors. On one “scavenging day” a certain craft omitted to hoist her two-hourly total and it was thought that she had not “scored” at all, while at the end of the day another craft proudly hoisted the figure 149 and “stood by” to receive the prizes of “Mars bars.” Within a minute or two, however, the craft which had omitted to hoist two-hourly totals hoisted a figure of well over 200! Captain Pugsley duly fined this vessel for not making the two-hourly reports, but even so he found that he had not got enough “Mars bars” to go round—an incident which, needless to say, was taken in good part by all concerned.
Apart altogether from the valuable work done in clearing floating wreckage and jetsam from the anchorage—it was landed at the end of each “scavenging day”—the rivalry which the system produced among craft working day and night in what Captain Pugsley afterwards described as “the most bloody awful corner in the world” (the north-eastern corner of the British Assault Area), proved of tremendous value to the morale of the crews.
In the eastern—the British—sector of the Assault Area the German minelaying effort continued to mount steadily for nearly a fortnight after D-day. So far as enemy action was concerned, the German mining campaign was the only source of the major anxiety felt by Admiral Sir Bertram Ramsay, the Allied Naval Commander-in-Chief. Admiral Ramsay was always confident that the mine menace would be overcome in the end, but he was acutely conscious of the great strain under which the crews of his minesweepers had to work day and night almost without interruption for long periods, and that as time went on more and more of these little ships began to show signs of requiring repair. All manner of defects were becoming apparent as the result of the frequent explosion of mines in close proximity to their hulls. Singly, these defects mattered little, but they threatened to have a cumulative effect. The repair and maintenance organisation on the far shore did wonders, and to the officers and men of this organisation must go much of the credit for keeping not only minesweepers but a host of other craft in running order when none of these could be spared to visit a British dockyard.
The concentration of mines in the Assault Area was such that on one occasion when a Minesweeping Flotilla of BYM’s switched on the electrical impulse gear one morning to begin sweeping for magnetic mines, no less than 23 mines “went up” in their vicinity within a few seconds. It was, as one of the officers feelingly said, “One hell of an explosion,” for the smallest of these mines contained seven hundred pounds of high explosive. There were several other occasions on which nine or ten mines detonated as soon as the electrical impulse gear was switched on preparatory to sweeping.
In order to cope with the situation produced by the large scale German mining offensive it was necessary for risks to be taken which would in other circumstances have been deemed unjustifiable. Moreover, everything possible was done to try to reduce and restrict the number of ships off the beaches and therefore in the danger area. So gigantic and rapid was the build-up of the strength of the invasion armies and of their requirements in equipment, vehicles and stores, that the average number of ships in the Assault Area was between three and four hundred. This was reduced to some extent during the height of the German mining offensive, but it could not be greatly reduced without effecting a corresponding reduction in the scale and the rate of the build-up of the Allied armies. Against this Admiral Sir Bertram Ramsay most resolutely set his face. Come what might, the armies should get all that they required both for maintenance and for reinforcement. Other means would have to he found to eke out the naval resources so that the difficulties imposed by the German mining should be overcame. The only “other means” possible entailed a further increase of the burdens of danger and responsibility imposed upon the minesweepers, but they responded without question. Even so, it was found to be quite impossible to keep the Assault Area swept and at the same time maintain all the wide swept channels leading to it which had by this time replaced the ten narrow swept channels running south from “Piccadilly Circus.” The anchorages had to be kept swept, so the minesweepers on this endless task had to be reinforced by some of those which had up till then been engaged in widening the cross-Channel routes and keeping them clear by daily sweeps. This meant a narrowing of the swept channels running across to Normandy from England. This was a serious matter, for the daily traffic in these channels amounted to sixteen convoys, with an average number of fifteen ships in each convoy—a total of nearly 150 ships a day exclusive of warship traffic and groups of landing craft. Nevertheless, it had to be accepted as the lesser of two evils.
By D plus 16 more than 90 ground mines had been accounted for in the eastern area alone, and on three of those sixteen days minesweeping had been quite impossible owing to the great gale. And in that time three ships had been sunk and twelve damaged by mines in the eastern area—an astonishingly low dividend for the German minelaying effort. It must be borne in mind that a ship sunk in the Assault Area did not only mean the loss of ship and cargo, but might well produce a navigational obstruction which would greatly impede and even endanger the movement of other ships. Such a contingency had to be perpetually borne in mind, for it could not but lead to a slowing down of the rate of the build-up of the armies. For this reason a special wreck-disposal organisation was in constant readiness to tackle and move or destroy any awkward wreck.
The s
everity of the German mining campaign in the Assault Area is illustrated by the following three extracts from the log of one of His Majesty’s ships in the Assault Area on the morning of 24 June:
07.30—HMS Swift (destroyer) blew up on mine on port bow.
07.40—Motor-transport ship blew up on mine on starboard beam.
08.10—Unidentified ship well astern blew up on mine.
If one examines the German minelaying campaign off the Normandy beaches as a whole, one finds that there was not very much difference between the degree of concentration in the German mining in the British and American areas. One would have expected rather more mines to be laid in the eastern area than in the western area because the former was slightly nearer to the main airfields used by the German aircraft employed on minelaying, and this proved to be the case—at least in so far as the number of mines accounted for was concerned.
From D-day to D plus 27 (3 July) the total number of mines accounted for in the Assault Area was 552. Of these 291 had been accounted for in the eastern, or British Assault Area, and 261 in the American or western area. In the British Assault Area 95 moored mines and 177 ground mines were accounted for between these dates, while there had been 19 ship casualties due to mines in the area. In the American Assault Area in that period 91 moored mines had been swept, 146 ground mines accounted for, and there had been 24 ship casualties due to mines. Among the ships mined in the British area in this period was the cruiser HMS Scylla, which was wearing the flag of Rear-Admiral Sir Philip Vian, commanding the Eastern Task Force. HMS Scylla had just reached her night patrol area on the north-east corner of the British Assault Area when she was mined at 10.56 p.m. on 23 June. Fortunately she was only damaged and was able to reach a British dockyard for repair, and Rear-Admiral Vian, who was unhurt, transferred his flag to HMS Hilary, which had been serving as headquarters ship to Commodore G. N. Oliver in JUNO area.
HMS Swift sinking off Normandy, 24 June 1944.
The German minelaying campaign did not end on 3 July, but there was no doubt that its back had been broken by that date. Later, the Allied Naval Commander-in-Chief in alluding to the German minelaying effort and the strain which it had laid upon our minesweeping resources, stated that in three months in the Assault Area off Normandy the numbers of mines swept amounted to rather more than 10 per cent of the total number of mines swept in all theatres of war in five years. When one reflects upon the great German and Italian mining campaigns, one begins to appreciate the degree of concentration of the German mining campaign in the comparatively small Assault Areas of “Operation Neptune.”
While the mining campaign was undoubtedly the Germans’ main and most important counter to the invasion of Northern France, Admiral Sir Bertram Ramsay, as Allied Naval Commander-In-Chief, had to take many other possible German moves into account and take steps to counter them. He certainly could not work on the assumption that the German Admiral Krancke would put all his eggs in one basket—even if the “eggs” were particularly devilish types of mines and the “basket” were the Assault Area. It had, of course, long been realised that one of the chief dangers to the anchorages and to the lifeline of invasion across the English Channel might come from U-boats. There was no doubt that Germany had several hundred of these craft at her disposal, and it was reasonable to suppose that the German High Command would appreciate that the defeat of the Allied invasion of Northern Europe would be essential to the future of the Third Reich, and would therefore attack its sea lines of communication with the utmost force. Moreover, the Germans had good and long prepared operational U-boat bases on the flank of the invasion lifeline in Brest and the Biscay ports. The Allied Naval Commander-in-Chief had, in fact, worked out on the basis of all available intelligence that up to 200 U-boats might attack the western flank by D plus 19, considerably over half that number being available to attack during the preceding ten days. It had also been known that the main reinforcements for the U-boat flotillas based at Brest and in the Biscay ports came from the Bergen and Trondheim areas of Norway.
It had been for this reason that Coastal Command of the Royal Air Force had been asked to concentrate a considerable force on anti-U-boat operations off the southern part of the Norwegian coast for some time before D-day, and some anxiety had been lifted from Admiral Ramsay at the very gratifying results of this offensive. The anti-U-boat offensive by Coastal Command of the Royal Air Force off the Bergen and Trondheim areas of Norway began on 16 May. By the end of May there had been no less than twenty-two sightings of U-boats. Aircraft had been able to attack on thirteen occasions, and it was estimated that at least six certain “kills” had been obtained. Between the end of May and D-day the operations were hampered by weather, but other promising attacks were made and probable “kills” listed.
These results told Admiral Ramsay that the Germans had, in fact, been trying to send reinforcements to the U-boat flotillas in the west to operate against the invasion, which the Germans must have known by that time to be imminent. They also indicated that such a high rate of certain loss and probable damage had been inflicted upon the intended reinforcements that those which arrived would bear small relation to those sent out and would be likely to begin their tasks in the west in a chastened mood. It was, in fact, more than likely that the majority had put back to the shelter of the Norwegian fiords rather than face the long and dangerous passage of the North Sea, Fair Isle or Faroes Channels, and the Atlantic in order to join their comrades in the Biscay ports. On the morning of D-day, moreover, Admiral Ramsay received reports which showed that the U-boats stationed at Brest and in the Biscay ports had not left harbour. Here was encouraging proof that the enemy, knowing invasion to be imminent, was unaware of the date on which it was to be launched.
As soon as the news of the Allied assault in the Bay of the Seine reached the U-boat flotillas, however, they reacted quickly. The U-boats hurried to sea and began to try to close in to the attack on the western flank of the invasion area and its lines of communication with the southern English ports. The Allies, however, were ready for them. It was the time of year when the nights were at their shortest, and therefore when aircraft held the greatest advantage over U-boats trying to make a rapid passage on the surface to the area in which they expected to attack. For this reason, coupled with the very great naval commitments, the outer and main defence against the approach of U-boats from the west was composed of aircraft of Coastal Command of the Royal Air Force. There were, of course, inner defences of anti-submarine vessels and convoy escorts, and these would have had to form the outer as well as the inner defences had the invasion been contemplated in conditions of winter light.
Coastal Command “saturated” the air off the western flank of the invasion and over the approach routes of the U-boats, and the aircraft did magnificent work. During the night of D-day they sighted eleven U-boats and were able to attack six of these; and on the night of D plus 1 they sighted ten U-boats and were able to attack seven of them.
It is worthy of note that no U-boat sightings took place during daylight hours, showing beyond possibility of doubt that our air and sea patrols were so disposed as to preclude the possibility of U-boats proceeding on the surface by day. This itself delayed their passage, for a U-boat’s surface speed was roughly four or five times that of its submerged speed, and there were less than six hours of darkness. The results of the air attacks on the U-boats could not be assessed with any accuracy, but even in the well-nigh impossible event of none of them causing even damage, each sighting meant that the U-boat was forced to dive and thus still further to delay its passage. Nor was that all. U-boats of the ordinary type such as the Germans used in the western part of the English Channel immediately after D-day could not hope to operate successfully in the narrow waters of the invasion area unless they arrived there with batteries and compressed air bottles fully charged—and this was impossible in the case of U-boats forced to submerge for long periods during their passage.
It was only after the attempte
d initial assault of the U-boats on the invasion area and convoy routes had been broken that the Germans tried to use U-boats fitted with the “schnorkel” device in this area. This device consists of a combined air intake and exhaust pipe which is telescopic and which enables the main diesel engines to be run, both for propulsion and for battery charging, while the U-boat is submerged. By enabling the U-boat to make long passages, below the surface and to charge the batteries while submerged, this device very greatly facilitates the operation of U-boats in narrow and coastal waters, particularly where there are many sea and air patrols.
Why the Germans did not use the “schnorkel” in the first U-boats sent out, instead of waiting until the chances of mounting any considerable U-boat offensive against the invasion had almost evaporated, remains a mystery. It almost seems as if the Allies had once again struck before the Germans were quite ready. As it was, they had no success, even with the “schnorkel,” against the Assault Areas off Normandy or against the cross-Channel convoy routes which were the vital lifelines of the Allied Armies of Liberation.
The ships of the Allied navies would undoubtedly have broken any attempt at a U-boat offensive just as surely as did the aircraft, but this in no way detracted from their gratitude to the air forces. “Neptune” was a combined operation in the true sense of the term; the navies had plenty to do and they had to guard the eastern flank against all sorts of varied forms of attack. It devolved upon the air forces to guard the western flank against U-boat attack, and this they did with very marked success.
U 185 photographed in August 1943 with the new schnorkel device. The schnorkel is partially raised and is presumably being lowered as the vessel surfaces.
In the Bay of Biscay and the approaches to the English Channel aircraft sighted U-boats on ninety-six occasions between 1 June and 3 July. Of these fifty-nine were attacked. Six U-boats and probably more, were sunk, others damaged and yet more discouraged. Off Norway, between the beginning of the anti-U-boat offensive in that area on 16 May and 3 July, U-boats were sighted on forty-four occasions; twenty-eight attacks were carried out, sixteen of which were classed as “promising”; and at least thirteen U-boats were probably destroyed.
Operation Neptune Page 24