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This extract is one of the most comprehensive accounts of the minesweeping operations that took place on D Day.

Source: http://www.ibiblio.org/hyperwar/USN/rep/Normandy/ComNavEu/ComNavEu-433.html 

Operation Neptune Minesweeping

Source: Historical Section, COMNAVEU. "Administrative History of U.S. Naval Forces in Europe, 1940-1946." vol. 5. (London, 1946): 301-337 [This manuscript, identified as United States Naval Administrative History of World War II #147-E, is located in the Navy Department Library's Rare Book Room.]  

Transcribed and formatted by Charles Hall for the HyperWar Foundation


PART V
'
NEPTUNE' MINESWEEPING OPERATIONS
 

A. Plans for Sweeping German Minefields

41.   The enemy's most dangerous available weapon, for employment against Allied ships and seaborne forces, was his sea mining. One of the major Allied naval tasks was therefore to protect NEPTUNE forces from enemy minefields. The naval plan was largely based upon the requirement for sweeping Allied forces through the mine barrier. Under the routing plan the Allied armada were to sortie, from numerous ports along the south-west, south and south-east ports of England, were then to converge on Area Z, proceeding along the British Coastal Channel, and were finally to turn southward, crossing the channel through the SPOUT, in order to approach the assault area. The minesweeping problem was to assure that those routes, the assault area anchorages, and the manoeuvring space were free of enemy mines.

42.   The enemy mine situation within these NEPTUNE waters, was as follows:

a.       Harbour entrances, (through which NEPTUNE forces would sortie after their final assembly) the British coastal channel, along which they would pass to the converging area (Area Z), and Area Z itself, were maintained in a mine-free condition by normal mine sweeping searches executed by Home Commands;

b.       There was, however, the possibility that the enemy, once he learned that the Allies were assembling in mass, would lay mines from the air in these waters;

c.       To the southward of Area Z the waters were unswept, but searches had indicated that no enemy mines had been laid north of 50 N latitude;

d.       The enemy was known to have laid a mine barrier across the northern limits of the Bay of the Seine;1

e.       Southward of this barrier, the enemy maintained a coastal shipping channel of his own, which could be expected to be free of enemy mines;

f.         There was no evidence of mines, inshore of the German coastal channel but intelligence was incomplete and there might be unknown minefields;

g.       There was no evidence of ground mines laid in the shallow water along the beach, but it was possible that there might be some, and it was also probable that, after the assault began, the enemy would lay more;

h.       The enemy had available quantity of aircraft with which he could lay mines after the assault was under way.2

43. The general plan for dealing with mines, in 'NEPTUNE' waters, involved five steps:

a.   The sortie and convoy routes, Area Z, and that part of the SPOUT lying north of the German mine barrier, were to be regularly searched up until D-1 and after D plus 2, but not immediately preceding the movement of the assaulting forces.3

b.   Ten channels, two for each assault force, were to be cut through the mine barrier.

c.       Transport areas, anchorages, and manoeuvring space for bombarding ships were to be searched and swept;

d.       The danger of ground mines in inshore waters was to be disregarded during the assault, but the areas were to be searched as soon as sweepers were available;4 thereafter sweepers were to stand by to sweep any ground mines the enemy might lay after the assault started.

e.       Channels were to be widened into one broad passage as soon as possible.

44. In view of this plan, and of the disposition of enemy mines, responsibility for all searching in and south of the "barrier", and for sweeping force Us lateral passage up to the barrier, was undertaken by the expeditionary forces. Responsibility for searching and sweeping, in NEPTUNE sortie and coastal channels, in Area Z and in the waters of the SPOUT north of the barrier, was left in the hands of the appropriate Cs in C Home Commands.

B. Minesweeping Arrangements in the Assault Area

45.   All minesweeping, in and south of the German mine barrier was undertaken by the Naval Expeditionary Forces. Responsibilities were divided as follows:

a.       ANCXF retained direct control of the initial ten approach channels through the mine barrier, for searching and sweeping the transport areas, and for subsequent widening the approach channel, by sweeping out areas between the initial channels;

b.       Task Force Commanders arranged for searching or sweeping anchorages, inshore mines, manoeuvring space for bombarding ships, and mines laid in the assault area after the assault;

c.       Each Task Force Commander delegated command of minesweeping in his area to a senior minesweeping officer who was responsible for operation of all minesweepers in each area, and for coordination with the activities of the two Task Forces.5  

46. The total strength of Allied minesweepers, engaged in the assault,6 was 255 vessels. This force comprised:

d.       twelve fleet minesweeping flotillas of 9 ships per flotilla;7

e.       six flotillas (of 10 ships each) of YMS type motor mine sweepers;8

f.         seven flotillas (of ten ships each) of British type motor mine sweepers;9

g.       four groups (of five ships each) of mine sweeping trawlers;10

h.       thirty-six R.N. mine sweeping motor launches;

i.         forty-eight R.N. danlayers; and

j.         nine miscellaneous supporting ships and craft.11  

47.   Provision of such a large number of minesweepers severely taxed Admiralty's resources. To meet the requirement, minesweepers had to be withdrawn from other important services. When the scale of the Assault was increased from a three to a five-division basis, requiring four additional channels to be cut for the two new assault forces, it was necessary to allocate four additional flotillas. One was a new flotilla, not commissioned until the eve of the operation; one was an ancient flotilla from the 1st World War; one was a decimated flotilla from the Mediterranean; and one a Canadian flotilla which had spent its entire career in escort duty.

C. The Passage and False Start

48.   The passage was technically defined as starting, when a vessel left the searched channels of the English coast and as ending, when it entered the swept channels of the mine barrier. The passage of all assault forces, except certain convoys of Force U, was through the SPOUT. The Assault Forces were not "swept" through this passage, as it was too short to enable minesweepers to precede the Assault Forces and still enter the barrier on time, as other minesweepers were not available for the job, and in view of the fact that no mines were known to have been laid in the area, as C in C Portsmouth had searched the SPOUT at the last possible moment.

49.   The route of Force U, from the West Country to the entrance of approach channels 1 and 2, lay through an unexplored area. Force U convoys sailed on 3rd June. Early on the 4th, the 14th end 16th Minesweeping flotilla sent sweeps to explore the route ahead of them. The 16th Minesweeping flotilla received the postponement signal, at 0840 on the 4th June, and turned back. The 14th Flotilla, which was further ahead, had not yet received the signal when they found mines. The senior officer detached a PT boat to report the minefield, but, the weather rapidly deteriorating, extricated his flotilla and turned to the westward.

50.   ANCXF considered that these mines were a chance lay, jettisoned by E-boats, and decided not to attempt to change the route of Force U. The following day, when the operation was resumed, the 14th Minesweeping Flotilla swept and buoyed a channel through the minefield, cutting one more mine. A PT boat was detailed to shepherd the following convoys through this channel. Further on, the 16th minesweeping Flotilla cut four more mines along this route. Force U passed safely through this minefield, but it claimed the first casualty of the operation, U.S.S. Osprey.

D. The Approach

51.   The Approach was technically defined as beginning, when the loading minesweepers of each Force began cutting through the barrier, and as ending, so far as minesweepers were concerned, when they had reached and swept the transport area. Two channels were cut through the mine barrier for each assault force in order to assure the safe approach of the five Assault Forces. Each channel varied from 400 to 1200 yards in width. Each Assault Force was also provided with: one "transport area" of searched waters, 4 to 6 miles long and some 2 miles wide, situated in the mine free German coastal convoy channel.

52.   Ten flotillas of fleet minesweepers were detailed to cut the 10 channels and to search the five "transport areas". Each flotilla consisted of nine fleet minesweepers, to which was attached four minesweeping motor launches, two Oropesa minesweeping "LL" trawlers, and four danlayers. The motor launches, equipped with light sweeping gear, preceded the leading fleet sweeps in order to clear a path for them. The "LL" trawlers swept for magnetic mines while the danlayers buoyed the channel, to guide the oncoming Assault Forces.

53.   In order to assure that the channels cut would be located in the proper positions, 10 - sonic underwater buoys were laid in positions to mark the edge of the enemy mine barrier in the Assault approach channels. These Buoys were laid so as to come alive on D minus 1, when they would be utilized by H.D.M.L's, acting as marker boats, to enable the minesweepers to commence sweeping the approach channels in the correct positions. Once sweeping was begun from the correct starting points, accuracy of navigation was aided by the use of QH and QM electronic navigational devices and by taut wire. The course of all the channels cuts were within 100 yards of their intended positions.

54.   To prevent the enemy from learning of the Allied approach, or of the area at which the Assault was aimed, until the last possible moment, it was essential that barrier cutting minesweepers should not operate too far in the van of the leading assault ships. The maximum speed of the leading craft in some channels was 5 knots the minimum safe minesweeping speed was 7 knots. The minesweepers were therefore required to lose approximately an hour and a half. They accomplished this by back-tracking for 40 minutes just before they came within range of enemy radar. Making two 180 turns with sweeps streamed was a difficult manoeuvre, further complicated by the tide. Before the appearance of German beach obstacles, H-hour was scheduled to be 3 to 4 hours before high water. On that basis the cutting of the barrier would have begun, on a weak east-going, and finished on a strong west-going, tidal stream. This would have permitted the whole sweep to be carried out in a "G" formation to starboard. The wasting of time could have been accomplished by tuning 180 degrees in succession, back into the swept channels. But because of the beach obstacles, H-hour was set at an hour or so after low tide. The sweep, therefore, started with a strong east-going stream, which, in the later stages, turned to a strong west-going stream.

55.   It therefore became necessary to begin the operation in "G" formation to port and to change sweeps at the change of the tide. A method of doing this, while wasting time, was devised and adopted with minor variations by the majority of flotillas. All ships, except the leader, recovered sweeps in succession from the rear and formed line ahead, protected by the leader's sweep. On completion ships successively turned 180 degrees, staring with the rear ship, and retired along the channel already swept. After all ships had turned, the leader recovered her sweep, turned and followed the others. When sufficient time had been lost, the flotilla turned 180 degrees together, streamed starboard sweeps and, reaching the last danbuoy, formed "G" formation to starboard. This was successfully tried out in practice by some of the flotillas. Most of them were unable to exercise the new manoeuvre as they had been employed during the last fortnight in clearing minefields laid by the enemy in his pre-invasion offensive, and in searching prospective NEPTUNE convoy lanes.

56.   This manoeuvre was successfully carried out by all flotillas, even though the 9th and 18th had to execute it in the middle of a minefield. The 6th flotilla was unable to lose as much time as planned because the leading landing craft in channel 5 were ahead of program. The latter part of this flotilla's sweep, therefore, had to be carried out at a speed of about 6 knots, but no mines were found in this channel. The enemy were not alerted by the approaching sweepers, although the 14th minesweeping flotilla, which was operating the lateral convoy route of Force U, and in the first approach channel, was in sight of the French coast from the afternoon of D minus 1.12

57.   During the passage and approach, the weather was heavy. This caused little trouble to the fleet minesweepers, but it made sweeping very difficult for the motor launches, which were, however, able to carry out their task. ML's cut two mines from the path of the leading fleet sweep of the 9th minesweeping flotilla. The danlayers also had trouble with the weather. Some dan lights ware smashed in launching, but the reserve danlayers filled the gaps. All channels were adequately marked and the Assault Forces found them easy to follow. Sweep cutters were met in Channel 5, but no mines were found. 29 mines were cut in Channels 2, 6 and 7. Throughout the approach, the leading minesweepers checked their positions by QM, QH, and taut wire measuring gear. In two cases one or the other method failed, but all flotillas succeeded in laying their terminal dans within a cable of the assigned positions and within a few minutes of the planned time. The five transport areas were searched on schedule, but no mines were found.

58.   Immediately the sweeping of the approach channels and transport areas was completed, the twelve flotillas of fleet minesweepers turned to three other urgent tasks:

a.       searching waters required for the movement of bombarding ships;13

b.       clearing lateral channels connecting the inshore terminals of the ten approach channels; and

c.       widening the approach channels.

These three tasks were executed concurrently. Three fleet minesweeping flotillas were detailed to the Task force Commanders for bombardment minesweeping, three for sweeping connecting channels, and two to standby for special requirements. The remaining four, operating under the direct control of ANCXF, immediately began sweeping out the areas in the German mine barrier lying between the approach channels. They were joined by the other flotillas carrying out this task, when the search of bombardment end lateral areas was completed.

59.   The intricate manoeuvres necessary to disengage ten flotillas in a confined space were successfully accomplished. In conducting the search of the bombarding areas some flotillas operated within two miles of the enemy shore. In this phase there was some mutual interference between minesweepers. Some of the searches planned were not completed before oncoming landing craft forced the minesweepers out of the way. These searches, however, revealed that the inshore areas were clear of moored mines. The ten narrow channels through the German mine barrier were inadequate to accommodate the requirements of the enormous post-assault cross-channel shipping program. When the fleet minesweepers had completed their assault tasks they were therefore employed in clearing the entire barrier between the first and the last approach channels. In so doing, they concentrated on merging two pairs of adjacent approach channels to make them available by the end of D-day, and their rejoinder with other minesweeping flotillas.

60.   The clearance of the space between channels 3 and 4 (known as channel 34) and between 5 and 6 (channel 56) was completed according to plan on D-day; Channels 12 and 78 were completed on D plus 1; Channel 14 was finished on a D plus 7; and channel 58 was cleared to a width of six miles by D plus 8. The entire barrier within the SPOUT was open by D plus 12. The clearance of the enemy mine barrier was carried far enough to the north to ensure that the whole of the minefields discovered during the approach was cleared. 78 moored mines were found in this field alone.

E. Sweeping the Inshore Waters

61.   Inshore waters, lying between the transport area and the assault beaches were not swept during the initial assaults. The risk of loss from mines in these waters was accepted because:

a.       it was not thought that the Germans had laid any mines in inshore waters;

b.       the project would have demanded more sweepers then were available;

c.       the delay which would have been required between the cutting of the barrier and the assault was unacceptable; and,

d.       minesweeping could offer little protection in any case, in view of the period delay mechanism with which enemy moored mines were equipped.

62.   Inshore areas, especially the boat lanes between the transport areas and the beach, and the areas of the artificial harbours were to be swept as soon after the assault as possible. For this purpose, each assault force was allocated one flotilla of YMS or BYMS, one flotilla of British Motor Minesweepers, and a group of 6 minesweeping LCT's. All three types of vessels were equipped with light sweeping gear especially designed for sweeping moored ground mines in shallow waters.14 Inshore waters were searched shortly after the first assault. But no mines were found until after the enemy began laying them from the air.

F. The Enemy's Minelaying Counterattack

63.   It had been anticipated that the enemy, after the assault, would counter attack strongly by laying mines in the assault and Build-up channels. This appreciation proved correct. In the first month after the assault, the laying of ground mines by aircraft by night was the enemy's chief weapon for impeding the Allied Build-up. This mine-laying forced the Allies to take risks, which had previously been considered unacceptable, inflicted casualties, and slowed up shipping movements. The effect on the Build-up was however negligible.

64.   The first indication of the extent of the ground mine problem came on D plus 1, when some 30 ground mines were detonated in the neighbourhood of the CARDONNET shoal in the UTAH area. It is uncertain whether this field was in place before the assault, with period delay mechanisms which prevented its discovery on D-day, or whether surface craft succeeded in laying it on the night of D-day. The field claimed seven casualties including two U.S. destroyers, the Glennon and the Meredith, the U.S. Destroyer Escort Rich, and the U.S. Fleet minesweeper Tide. In the eastern area also the air mining effort mounted steadily. It soon became apparent that the sweepers were not keeping pace with mines dropped in the channels and anchorages. Fifteen casualties, three vessels sunk and twelve damaged, were suffered in the ETF area by D-plus l6, while some ninety mines had been swept.

65.   On 24 June it was discovered that the Germans had been using a new and secret type of mine (the pressure mine), which was unsweepable by existing Allied methods.15 To counter this danger, a series of measures were taken which were effective in reducing sharply in casualty rate, then confined mainly to near misses on sweepers. The following were the steps taken:

a.       Airfields, from which enemy minelaying aircraft were operated, where heavily and repeatedly bombed;

b.       Allied night fighter aircraft cover was increased and special attention was given to the intercepting of minelayers;

c.       the width of ship channels was reduced, while all available minesweepers were concentrated on these narrower waters;

d.       to reduce pressure caused by the movement of ships, speed restrictions were imposed can all vessels operating in mined waters;

e.       when it was necessary to move heavy ships in such shallow water that their speed could not be reduced to a safe figure, tugs were employed with a long tow, in order to avoid pressure and acoustic actuations being applied simultaneously;

f.         when it was discovered that a swell would reproduce the pressure conditions required to fire an acoustic "oyster" mine and that lower speed would then be no protection all movements were stopped when such conditions existed, until channels had been swept;

g.       it was also learned that period delay mechanisms could be worked off without pressure actuation. Sweeping schedules were accordingly adjusted, under swell conditions to cover as large an area as possible of all channels and anchorages.  

G. Minesweeping at Cherbourg

66.   The early capture and employment of a major port on the Far Shore was essential to OVERLORD. Without it the Allied armies could not be adequately supplied. The Germans, fully realizing this fact, sought to prevent the Allies from capturing Cherbourg and from putting it quickly in workable condition. The German plan to make Cherbourg unworkable included provision for sowing the approaches, channels, anchorages, and berths, with a profusion of mines.  

67.   NCWTF put Commander M/S West in charge of the operation of clearing mines from Cherbourg. Intelligence data available, as to the extent of mining in and off the harbour, was of great assistance in framing for this difficult clearance.16 Before Cherbourg was taken, during the northward advance of the U.S. Army along the Cotentin Peninsula, channel "L" was extended along the east and north coasts to protect bombarding ships employed in support of the Army's advance. During these operations, the minesweepers 17 repeatedly came under fire of shore batteries. Within 24 hours of the silencing of the last battery, "H" and "L" channels had both been established and an area off the harbour entrance cleared to seaward of the 10-fathom line. The clearance of moored mines, within the 10-fathom line outside the harbour was effected by the two U.S. YMS squadrons, the 167th BYMS, and 206th MMS Flotillas.

68.   Inside the harbour, the principle adopted of first clearing as much of the Grande Rade, as was necessary to gain access to the Petite Rade, and enough of the latter to provide a passage to the Avant Port de Commerce and to the Nouvelle Plage. Each lap was first searched for snag lines by LCV(P)s. A passage was then swept by ML's wide enough to start Oropesa clearance with YMS. Ground minesweeping of each lap was started, as soon as it was safe from moored mines. Motor launches and LCV(P)s were used for clearing very confined spaces in which not even a YMS could manoeuvre.

69.   At the same time, two "P" parties of Commodore Sullivan's port salvage organization searched Bassin Des Flots, the Avant Port de Commerce and the shallows of the Nouvelle Plage, working outwards to meet the sweepers. To avoid danger to "P" party divers from exploding mines, these parties worked only for three hours either side of low water. The mine-sweepers worked three hours either side of high water. Entry to the landing point, most easily reached, having been made as rapidly as possible, clearance was extended to the docks and basins which had been more thoroughly blocked. Cherbourg port was free of mines and was receiving ships by 29 July.

H. The Score

70.   Ships lost to enemy mines, and mines accounted for between 4th June and 3rd July were:

 

Western Task
Force

Eastern Task
Force

Total

Casualties

24

19

43

Moored mines swept

91

95

186

Ground mines swept

140

109

249

Ground mines accounted for other than by minesweepers

6

68

74

 

261

291

552


Footnotes:

1 This barrier was thought to extend northward from latitude 50 N to a line, running 092 and 328 from a position 4927' .5 N and 0 54' W. See ON 6 para. 5.)

2 The exact number was uncertain because the enemy could easily employ craft for this purpose which were normally bombers.

3 ON 6, Para.16. During the assault phase all available sweepers would be engaged with the mine barrier or inside the assault area. The risk was not great as the British coastal channel was normally constantly searched, the area north at barrier was not believed to have mines in it, and it was searched during the weeks before NEPTUNE just to make sure.

4 Because (a) there were insufficient sweepers to search them, (b) no mines were thought to exist in these waters anyway, and (c) in any case, ground minesweeping ahead of forces could not give security in view of the period delay mechanism with which the mines mere equipped.

5 ANCXF Report, Appx.14.

6 Operations in and south of the German mine barrier.

7 These were the 1st, 4th, 6th, 7th, 9th, l4th, 15th, 16th, 18th, 31st and 40th R.N. minesweeping flotillas and the 7th U.S.N. minesweeping squadron.

8 Four flotillas, the 150th, 159th, 165th, and 167th M.S.F. were British and two Y-1 and Y-2 were American.

9 The 101st, 102nd, 104th, 115th, 132nd, 143rd, and 205th R.N. MMS flotillas.

10 The 131st, 139th, 159th 181st R.N. Groups of "LL" trawlers.

11 For details of ships and craft taking part in the minesweeping operation and their organization see ON 6, Appx.II.

12 As will be seen in Chapter VIII, Section 8, this flotilla was screened from radar detection by Allied Radar counter measures.

13 In order to safeguard the bombarding battleships, cruisers, destroyers, and other ships which would be required to move around in the congested assault area, often very close to the shore, it was considered essential that their movements should be preceded by minesweeping. Bombardment was to begin before H-hour so that no time could be wasted between the completion of sweeping the approach channels and transport areas and the beginning of sweeping for bombardment forces. The areas which were swept are defined in ON 6, Appx.I. For diagrams see ANCXF Report Vol I,Appx.l4 and ANCXF Report Vol.III,Annex H.

14 See ANCXF Report,Vol.III,p.63. It was originally planned to use also LCV(P)s equipped with very light gear for work very close to shore, but in trials it was found that the gear broke up before the craft could reach the shallow water.

15 This was a pressure acoustic mine which depended for actuation on both the increased water pressure caused by a ship passing in its immediate vicinity and the sound of the ship. Another variation was the pressure magnetic mine.

16 Two rows of G.Y. mines with snag lines and 8 ft. of 5/8th inch chain moorings had been laid across the eastern entrance of the GRANDE RADE. The western entrance was similarly blocked with mines with delayed release sinkers. The GRANDE and PETITE RADES shoreward of the ten fathom lines were well fouled with "Katies". There was a line of G.Y. mines across the entrance to the PETITE RADE and both RADES had been well sprinkled with acoustic, magnetic, moored and apparently delayed release moored mines.

17 The 7th USN Minesweeping Squadron and the 9th and 14th RN Minesweeping Flotillas.


  

PART IV
ASSAULT AREA: SCREEN AND ESCORTS

A. Allied Naval Dispositions.

ANCXF assigned to the appropriate Task Force Commander the task of screening the assault area against enemy naval penetration. Enemy naval forces within the Channel consisted of an indeterminate number of human torpedoes, self-exploding pilotless surface craft, sea mines to be laid by aircraft, and the 195 miscellaneous vessels in the preceding section.

To repel these enemy forces, the Task Force Commanders established an area screen, detailing to it, a proportion of the vessels allotted them by ANCXF. Manning the area screen required a careful phasing in the use of vessels. Until allied forces arrived in the assault area, there was no screen. On arrival, a proportion of the escorts and patrol vessels took up screening patrols. Still later, other vessels, which had completed their initial tasks of boat control, close fire support, or some other job, took over patrol duties, while a proportion of the escorts returned to the U.K. in company with the convoys. In due course, most vessels capable of escort duty, were transferred to C in C Portsmouth for escort duty to facilitate his task of operating the post assault build-up convoy program.2  


B. Eastern Task Force.

Naval Commander Eastern Task Force delegated control of naval forces screening his area to an authority known as "Captain (Patrols)"1 During the assault phase, this authority was stationed in the ETF flagship. Later he exercised control from R.N. headquarters on the Far Shore. In both cases, he was provided with full details of the position and movement of all objects in the channel, from the radar facilities of C in C Portsmouth, NCWTF and his own ship and shore radar.

The system of defence employed in the eastern area was the following:

a.      constant patrols to seaward by corvettes, trawlers. and sometimes destroyers were carried out;

b.      every 24 hours one Division of four destroyers was detailed as duty division for the entire area while two other destroyers were detailed as guard. for areas O and J. By day, these destroyers performed such other tasks as were assigned, but they were subject to call in case an attack threatened. By night they were posted as directed by Captain (Patrols). In neither case did they actively patrol up and down the defence line. The plan was that Captain Patrols would vector them against enemy forces, whose presence was discovered by radar or other means;

c.      during the hours of darkness or low visibility, this defence was augmented by a line of minesweepers anchored 5 cables apart along a defence line parallel to the shore and six miles to seaward;

d.      this defence line was continued down the eastern flank by a line called the TROUT line, composed of LCG's and LCF's, anchored 1 cable apart. The duty of the minesweepers and Landing Craft on this defence line was to prevent all enemy ships and craft from entering the British Assault Area, to illuminate the outer areas when ordered and to counter attack any submarine detected;

e.      two or three divisions of MTB's were stationed, stopped but under way, to the North eastward of the N.E. portion of the defence line;

f.       two or three sub-divisions of destroyers were stationed on patrol, to the north of the western half of the area, and sometimes to the northward of the MTB's;

g.     other light forces were stationed close inside the defence line, to act as reinforcements or as "pouncers". B.Y.M.S. and M.M.S. were anchored as minespotters, originally in the approach channels, but later in the lateral swept channel established within the area;

h.      these defences were augmented by a smoke screen laid by specially fitted craft at dawn, dusk, and as required.

The enemy's day activity was limited to one long range torpedo attack, by torpedo boats from LE HAVRE, at 0450 on D-day. This attack caused the loss of the Norwegian destroyer Svenner. The attack was assisted by the smoke screen laid by Allied aircraft to cover the eastern flank of the assault from batteries in the Le Havre and Villerville areas. The enemy vessels, were however, engaged, and one torpedo boat was hit by Warspite with 15-inch salvoes and was considered sunk.

By night the enemy's attack was more determined. On four occasions he operated torpedo boats, and on eight occasions E and R-boats, in the eastern Task Force area. On every occasion except one these forces were intercepted and forced to retire. In no case was any success obtained by enemy. The line L.C.G. and L.C.F., anchored on the eastern flank took a heavy toll of the human torpedoes which attacked in July. Two enemy torpedo boats were also damaged, five E/R boats sunk, and E/R boat probably sunk, three E/R boats badly damaged, four E/R boats damaged. E.T.F. casualties were two boats damaged with three killed and ten wounded.  
 

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