At the end of April, however, reconnaissances reported that the Germans were very largely increasing the number and effectiveness of the obstacles which they placed on the beaches between high and low water. An enormous number of aerial photographs of these obstacles were taken, many of them by aircraft which skimmed only a few feet over the water and the beaches in order to obtain photographs taken as nearly as possible horizontally. Reconnaissance parties were even landed on the beaches of France—chiefly in the Pas de Calais area—in order to make detailed examination of these obstacles.
It was at once obvious that these beach obstacles between high and low water marks were extremely formidable. They were of four main types. There were concrete pyramids to which were attached old French shells fused to act as contact mines; there were heavy timber ramps ten feet long specially designed to trap landing craft and fitted with Teller mines; there were thick stakes made of the trunks of young fir trees, eight or ten feet high and fitted with mines or fused shells; and there were “knife rests” made of railway line or angle girders, some of which were fitted with fused shells.
The appearance of these formidable obstacles quickly settled the problem of at what state of the tide the initial landing should take place and whether it should be in darkness or daylight. To attempt a landing at anything but low water would be to invite most serious loss among the landing craft and the troops and vehicles embarked in them, and would probably lead to the approaches to the beach becoming so encumbered with wrecks as seriously to impede succeeding waves of the assault. Moreover, daylight would be essential if the obstacles were to be avoided and removed.
An aerial reconnaissance photograph showing obstacles on one of the beaches.
It was therefore essential that the initial landing should take place at or near low water and in daylight. This decision was taken at a meeting between General Eisenhower and Admiral Sir Bertram Ramsay on 1 May 1944. The decision, of course, narrowed down the choice of D-day and of H-hour, for there are not many days in the month when low water at any particular place occurs soon after daylight.
The appearance of these German beach obstacles led to other developments. The problem of finding the best way of dealing with them, and of training men in this work in the very short time available had to be faced and solved.
To this end similar obstructions were constructed and placed on a beach in the United Kingdom where the rise and fall of the tide was about the same as that in the Bay of the Seine; experiments were carried out, and men specially trained in the removal of these obstacles while working in water. These men were given the title of LCOCU’s, which stands for “Landing Craft Obstacle Clearance Units.” They have since become popularly known as “Frog Men.”
In the weeks before D-day the enemy was very active in other ways, which is hardly to be wondered at since he was very nervous and his nervousness was being purposely increased by the Allies.
Coast Guard-manned LCI(L)-85 during a practice landing at Slapton Sands. The “85” would be pummelled by enemy fire during the invasion and sank in the English Channel on D-Day. It was at Slapton Sands that the enemy E-boats delivered there devastating attack during ‘Exercise Tiger’.
As early as March it had been noted that there had been a considerable increase in the enemy’s mining activity, particularly by E-boats in the Channel. In April there had been a great deal of patrolling by E-boats, while the German destroyers normally based on Brest had also shown unusual activity. It was the E-boats which were to inflict the first losses on the Allied invasion forces. This was during one of the final exercises. On the night of 28 April, E-boats attacked a convoy of LST’s (Landing Ship, Tanks) taking part in a rehearsal. Two American LST’s were sunk and a third damaged. The loss of life was tragically high, over 600 men being killed, while nearly a hundred were wounded. It was ironical that the E-boats should have scored a bigger success against the Allied invasion forces during a rehearsal than they were ever to do during the invasion itself, but it is interesting to note that the E-boats were in complete ignorance of the fact that they had attacked a portion of the Allied invasion forces. This was shown by the fact that the Germans promptly broadcast the quite ordinary and usual claim that they had sunk three ships in convoy.
On the very next night the German destroyers put in an appearance and were in action with the Canadian destroyers Haida and Athabaskan. In this action HMCS Athabaskan was unfortunately torpedoed and sunk, but one of the German “Elbing” class destroyers was driven ashore in flames and became a total loss.
The Allied minelaying campaign designed for the general protection of our shipping in the Channel during the invasion, and more particularly for the protection of our assault and bombarding forces, was meanwhile being carried out. It had begun on 17 April, and by D-day nearly 7,000 mines had been laid in this campaign. They included many mines of a new type specially designed for use against small fast vessels such as E-boats. Forty-two per cent of the mines laid in this campaign were laid by the Royal Navy in no less than 66 operations, while fifty-eight per cent were laid by aircraft on 1,800 sorties. The scope of this minelaying campaign stretched from the Baltic to the Bay of Biscay.
The decision to deliver the initial assault as soon as possible after low water and as early as possible in daylight hours had a profound effect upon the minesweeping plan. The choice of D-day and H-hour meant that the sweeping of the ten channels to Normandy from the “Piccadilly Circus” of swept water south of the Isle of Wight would have to be begun with the tidal stream setting strongly to the eastward, while the tidal stream would have changed in direction to a strong west-going current before the sweeping of the approach channels could be completed. This problem of carrying out a minesweeping operation across the tide with a complete change of the tidal stream in the middle of the sweep had never before been mastered, for in nearly all minesweeping operations the time and state of the tide can be chosen to suit the minesweepers.
In “Neptune” the time factor was also a problem to the minesweepers. The minimum efficient sweeping speed of the minesweepers was 7½ knots. At slower speeds the sweeps would not ride out from the minesweepers and would not have enough power to cut the moorings of the mines. On the other hand, the maximum speed of many of the landing craft which were to lead the assault was little more than 5 knots. Thus, even if the first groups of landing craft left “Piccadilly Circus” immediately astern of the minesweepers, the latter would reach the French coast an hour and a half before the assault craft. For the minesweepers to wait about close off the French coast for an hour and a half in the growing light would obviously lead to heavy casualties and a complete; absence of surprise. It followed, therefore, that means had to be devised whereby the minesweepers could waste an hour and a half while still a reasonable distance from the French coast and before daylight. Minesweepers, however, cannot just stop and waste time in the middle of a sweep.
The problems of wasting time and of dealing with the change of direction of the tidal stream were solved together by the introduction of an intricate manoeuvre which had never before been attempted. In order to describe this manoeuvre it is necessary to give a brief outline of some of the principles of minesweeping which were involved.
The type of sweep which is almost universally used today is that known as the “Oropesa Sweep,” because by its use only one vessel of a flotilla is in danger when sweeping through a minefield.
The Oropesa Sweep is a single sweep wire, serrated to saw through mine moorings, which runs out from one quarter of the minesweeper. At the outer end of the sweep wire is an “otter,” which is a structure of inclined planes which carries the end of the sweep wire far out from the wake of the minesweeper when it is towed through the water. On the surface above the “otter” is the “Oropesa float” which marks the end of the sweep wire and thus the edge of the water swept by that particular minesweeper.
Minesweepers usually sweep in flotillas of six ships, with two spare minesweepers and danbuoy-layi
ng vessels to mark the edges of the swept water. Each minesweeper keeps just within the edge of the swept water, which is traced by the Oropesa float of her next ahead. Thus only the leading minesweeper is in unswept and dangerous water. In practice the leading minesweeper is given a good measure of protection by being preceded by two shallow-draught motor launches, each with small Oropesa sweeps and sweeping a narrow lane for the leading minesweeper. The danbuoy-layers do not mark the actual edges of the swept water, but follow the second and the last minesweeper, so that there is a factor of safety on each side of the channel equal to the width of the swathe swept by one minesweeper. This factor of safety is necessary to allow for the sway of the danbuoys at the ends of their moorings in obedience to tide and wind. The spare minesweepers follow in the swept water with their sweeps “at short stay,” ready to take the place of any minesweeper whose sweep may be cut by an exploding mine or anti-sweeping device.
The attached diagram shows the formation of a minesweeping flotilla while sweeping a channel.
Every ship at sea is affected by tidal streams and currents, and if a ship is to “make good” a certain course when steaming across a tidal stream she must make due allowance for it and “steam into it” to an extent dependent upon the relative speeds of ship and current.
No type of ship is as greatly affected by tidal streams as the minesweeper when sweeping, for the sweep as well as the ship is influenced by the movement of the element in which they are working, while for them accuracy in the course “made good”—not only by the minesweeper but also by the sweep—means the safety of the ships which are to use the channel. With an “Oropesa Sweep” the minesweeper can steer into the current or tidal stream and so make due allowance for it, but the “Otter” and “Oropesa float” at the other end of the sweep wire cannot, and so the outer end of the sweep will be carried “down stream.” If the minesweeper is “up stream” of her sweep this is all to the good, for it will widen the swathe swept by the sweep; but if the minesweeper is “down stream” of her sweep the sweep will be carried in towards her wake and the strip of water swept will diminish—to vanishing point in the case of a strong cross-tide.
It follows therefore that, when sweeping across a tidal stream of any appreciable strength, the minesweeper must be “up stream” of her sweep. In other words, when sweeping across a tidal stream running from port to starboard the sweep must be out on the starboard side of the minesweeper, and vice versa.
It has been said that the date and time of D-day and H-hour made it necessary for the sweeps from “Piccadilly Circus” to the assault area off the Normandy coast to begin when there was a strong east-going tidal stream and finish when there was a strong west-going stream. This meant that the minesweepers had to begin their tasks with their sweeps out on the port side and finish their tasks with their sweeps out on the starboard side.
This problem was not a simple one of getting in the port sweep and getting out the starboard sweep. It entailed changing the formation of each minesweeping flotilla from port quarter-line to starboard quarter-line. Moreover, the whole operation had to be performed in such a way as to ensure that no minesweeper should enter unswept water and, above all, that no “holidays” of unswept water were left in the channels.
The working out of a manoeuvre which would meet all these requirements was indeed a puzzle, but it was solved in a most ingenious way, and in a manner which also provided the minesweepers with an opportunity of wasting time without risking the presence of unswept mines in the channels.
The solution was as follows. When the time came to reverse the sweeps the ships got in their port sweeps in succession, beginning with the last sweeper of the flotilla. As each sweeper got in its sweep it formed astern of the leader. The flotilla therefore reached a formation in which the ships were steaming in single line ahead, all protected by the sweep-wire of the flotilla leader, who was in turn protected by the two mine-sweeping motor launches ahead of her. There was now, of course, no “swept channel” in the accepted sense of the term—only the narrow lane swept by the flotilla leader. The end of the swept channel proper was marked by the last danbuoys laid just before the rear minesweeper hove in her port sweep.
Having reached this formation of single line ahead the minesweepers turned 180 degrees in succession, the rear ship being the first to turn. When it was the flotilla leader’s turn to put her helm over she hove in her sweep. Thus the whole flotilla was steaming in single line ahead, the rear ship leading, back along the narrow lane of water previously swept by the leader, and so back into the swept channel proper.
Once back in the swept channel the minesweepers could steam back to the northward until they had wasted the necessary amount of time. Then they turned again on to a southerly course, streamed their sweeps on the starboard side, took up their sweeping formation, and continued to sweep the channel on from the last danbuoys placed before the manoeuvre was begun.
It was a complicated manoeuvre, and time was desperately short for practising it before it had to be carried out on the way to the invasion, with the lives of thousands of men dependent upon the accuracy of the minesweeping and the success of this unprecedented manoeuvre. That it was done, and done successfully, in darkness under “action” conditions, speaks volumes for the skill, seamanship and coolness of the men who commanded and manned the minesweepers.
On 3 and 4 May 1944 there took place the final rehearsal exercise for “Neptune.” This was called “Operation Fabius,” and it went off successfully without any interference from the enemy.
By that time the meteorological organisation was already hard at work. Stations as distantly separated as Spitzbergen, Iceland, Greenland, the Atlantic coast of North America, the Azores, and West Africa were sending in weather reports and data, and these were supplemented by reports and data provided by specially equipped weather-reporting ships stationed far out in the Atlantic Ocean. Time was when the Royal Navy had hunted down German weather reporting ships sent out to provide data for the forecasts which the Luftwaffe used in planning its big raids. Now we sent out weather reporting ships and there were no German surface ships and few U-boats to distract their attention from their instruments.
With all the data from these widely separated reporting stations the meteorological experts attached to the staff of the Allied Naval Commander-in-Chief were keeping a constant watch on the weather trends.
It was on 8 May that it was decided at a meeting between General Eisenhower, Admiral Ramsay, General Montgomery, Air-Marshal Leigh-Mallory and others that D-day was to be 5 June, with 6 June as a “spare day.” It was laid down that 7 June could be used if this was absolutely essential, but there would be disadvantages of tide on that day which made it possible only as a last resort. If the invasion had to be postponed beyond 7 June it could not take place for another fortnight.
It was on 23 May that General Eisenhower, the Supreme Allied Commander, signalled to the naval, military and air commanders that D-day was to be 5 June. Everything was ready for the greatest inter-Allied undertaking in the history of warfare.
In the days before D-day the forces assembled to take part in “Operation Overlord” were visited by many distinguished persons. At the final “briefing” by the Commanders-in-Chief at No. 21 Army Group Headquarters on 15 May, His Majesty the King, Mr Winston Churchill and General Smuts were present, and all three of them addressed the senior officers gathered for that momentous meeting. On the previous day the British and Australian Prime Ministers had visited Admiral Sir Bertram Ramsay’s battle headquarters.
On 21 May Mr A. V. Alexander, the First Lord of the Admiralty, visited the headquarters of the Allied Naval Commander-in-Chief at Southwick Park, near Portsmouth.
On 24 May His Majesty the King visited Rear-Admiral Sir Philip Vian’s Eastern Task Force, and on the following day he visited the Western Task Force, which was the United States’ naval component under the command of Rear-Admiral Alan G. Kirk.
On 28 May H-hour was fixed and signalled.
It is, in fact, erroneous to speak of H-hour as if it was a touch-down time for the assault on all five beaches. Conditions of tide made it necessary to name five different H-hours—one for each beach to be assaulted, but these times were as close together as possible and were all between a few minutes before 6 a.m. and a few minutes after 7 a.m.
An artillery unit bound for Normandy loads equipment into landing vessels in Brixham on the southwest coast of England, 1 June 1944.
In those days before D-day the weather was the factor uppermost in the minds of all the high commanders, and it caused them no little anxiety. In May there had been a long spell of quiet fine weather which had extended into the first days of June. By 2 June, however, the meteorological experts had begun to shake their heads and frown over the weather charts which they compiled from the reports of distant stations. There was no doubt that the prolonged fine weather system was beginning to break up. Would it give place to another fine weather system or would it yield to a period of uncertain and stormy weather? That was the vital question, upon the answer to which hung the fate of millions and maybe of nations. A long postponement of D-day would have consequences too appalling to contemplate. It would almost certainly jeopardise all security and make the task of invasion infinitely more difficult when it could be launched. It would have a most adverse effect upon the morale, not only of all the men who were anxiously awaiting the signal to sail, but upon that of the forces of freedom all over the world. It would reduce the period available before the storms and rains of autumn set in and would therefore almost certainly greatly retard the march of the grand strategy of the United Nations.
Operation Neptune Page 14