WORLD WAR II
Content:
Minesweeping in the Second World War
Mining and Mine Countermeasures in World War II - Another Look at UK and Europe
Minesweeping in the Second World War
A year by year history by Nick Stanley
Author’s Comments: This is a series of articles, in which I hope to give a broad overview of (British) minesweeping in the Second World War. The account builds upon information I had initially gleaned when researching the war history of the Algerine Class, which was then recounted in the Twitter feed @AlgerinesAssoc (now dormant). I then decided to expand this research to cover all aspects of RN minesweeping, and this can now be found in the Twitter feed @Sweepers3945 which gives a day-by-day account, 80 years on, of what our mine warfare forces were doing in the war. At the time of writing, we’re on 3 April 1940, and if you hurry you’ll catch the Norwegian Campaign!. A glutton for punishment, I then decided to pull together all my scribbled notes to write a narrative account of the war against the mine. Initially, this was being done for my good friends in the Algerines Association; but I am deeply honoured that I’ve now been asked to contribute the completed article to the Vernon Link website. Despite its length, the narrative is far from exhaustive and there will definitely be omissions. Also, given my own limitations as an amateur historian, there will be mistakes. For both omissions and errors, I offer my apologies.
Nick Stanley
LMCDO 81
Commodore, Royal Navy (Retired). 3rd April 2020
The following article is Copyright © 2020 Nick Stanley. All rights reserved.
For a Day by Day history of Minesweeping in WWII click here.
Prelude
The First World War concluded with 726(1) vessels of the Royal Navy & Royal Navy Maritime Reserve engaged in minesweeping. Over 28,000 mines had been swept during the conflict, but the cost had been high; 214 sweepers had been lost in addition to 5 battleships, 3 cruisers, 22 destroyers and 4 submarines. The threat posed by the mine – around 586 Allied ships were lost, totalling around 1,000,000 tons – was such that it had to be taken seriously as tensions rose in 1939. Although mistakes would be made, the Royal Navy was determined that it would be ready when hostilities broke out on 3 September 1939, and from the very beginning of World War 2 its minesweeping forces were at the forefront of the war at sea. As in the First World War, trawlers would play a vital role in defeating the mine in the coming conflict, but they were limited by deck space and speed. Paddlewheel steamers- with higher speeds and larger deck-space - had been used highly successfully to supplement the trawlers during the Great War, and would do so again. However, for Fleet activity neither of these vessel types would be suitable and therefore the burden for major operations would be placed on the Fleet Minesweepers. At the outbreak of war these were the ‘Hunt’ or ‘Aberdare’ Sweepers – known more affectionately as “Smokey Joes” due to the tell-tale clouds emitting from their funnels – and the larger ‘Halcyon’ class. On the drawing boards, but yet to be laid down were the small but highly capable ‘Bangor’ class.
The ‘Smokey Joes’ were coal-burners (hence the smoke!) and 27 were available for service at the onset of hostilities. However, many were only just emerging from reserve and they were scattered around locations as distant as the Far East. The steam-powered Halcyons – of which there were 21 - were larger vessels, capable of minesweeping and escort duties. They were to perform both roles valiantly – particularly on the Murmansk Run - stepping back from anti-submarine duties only when corvettes started to enter service in significant numbers.
Although hostilities were formally declared on the 3rd September 1939, preparations were already in hand for an anticipated German mine offensive. Since the Munich crisis of 1938 the Admiralty had been raising the readiness of naval forces and trawlers were already being taken in hand for conversion. These included Admiralty Trawlers such as MYRTLE(2), LARCH, OAK, TAMARISK, ALDER & BERBERIS; purchased in April ’39, fully RN manned and fitting out in June ’39 with Oropesa sweeps at Chatham. These would provide an effective counter to contact mines, but against the magnetic threat the RN was less ready. These mines had seen use in 1918, but had not been particularly effective and it was already understood that a knowledge of the magnetic settings would be essential in developing an effective counter. Nonetheless, magnetic sweeping trials were taking place in the Solent in August 1939 although, regrettably, funding for the development of a mine destructor ship had been cut from that year’s Naval Estimates.
Immediately after the Spithead Review in July ’39, the 1st Minesweeping Flotilla (‘Halcyons’) conducted intensive minesweeping training off the South Coast before deploying to its war station at Scapa with the Home Fleet. Meanwhile, trawlers – an increasing number being taken up from trade and fitted with sweeps – were working up from Sheerness. These were now being manned by RNR crews and the Sheerness force would go on to be the immediate response to German attempts to close the Thames once the war started. To ease the loading on Sheerness, HMS SPARROW’S NEST at Lowestoft was activated on 1st September 1939 and would become increasingly vital in converting trawlers to minesweeping duties.
On 3rd September 1939, the RN stood ready to face the German mine threat with 36 Fleet Sweepers (of which 15 were deployed at foreign stations) and 40 minesweeping trawlers. The threat would not be long in emerging; German U-Boats of the 1st Flotilla were already at sea and poised to start minelaying off our East coast.
(1) Of these, only 110 were ‘regular’ naval minesweepers, the remainder being paddle steamers, fishing vessels and even barges.
(2) HMT MYRTLE was lost with all hands on 15 June 1940 off Kent whilst trying to recover a magnetic mine on deck.
For a day by day history of Minesweeping in WWII click here.
1939
The Second World War did not arrive unexpectedly out of a clear blue sky and prudent measures were already being taken in the Summer of 1939 to prepare a minesweeping force to meet the anticipated challenge. These measures included the conversion of trawlers into minesweepers; a process the Admiralty had started in Spring 39. Training for the new crews took place at sea throughout that Summer from bases such as as Sheerness & Chatham. With war drawing closer, Sparrow’s Nest at Lowestoft was activated on 1 September 1939 for trawler conversions. War’s outbreak on 3rd September 1939 saw the RN’s sweeping force stand at 36 Fleet Sweepers & 40 Trawlers crewed by 2000 personnel. The Fleet Sweepers – designed from the start as RN warships – were of the ‘Halcyon’ and ‘Hunt’ classes, but the latter were always known by the tell-tale that always accompanied them at sea: ‘Smokey Joes’.
The coal-burning ‘Smokey Joes’ had entered service at the end of the First World War and were the RN’s first purpose-built minesweepers. They displaced around 700 tons and had a crew of 75. Armed with a 4” gun, they had no Asdic and could only conduct mechanical sweeping. In 1939 nearly all of the Navy’s 26 ‘Smokey Joes’ were in Reserve and dispersed across the Medway (3), the Med (9) and the Far East (9), but - as with trawler conversions - they were being rapidly readied for operations. The ‘Halcyons’ were modern vessels that had been laid down from 1933 onwards. Fitted with Asdic and (later in the war) radar, they were very capable, well armed minesweepers that could also fulfil an important escort function.
The ‘Halcyons’ were split into two Flotillas: 1st MSF closely supporting the Home Fleet at Scapa and the 5th MSF based at Dover for North Sea duties. With most of the ‘Smokey Joes’ overseas, and despite the trawler conversions, it was clear that more hulls would be needed and so a number of paddle wheel steamers were taken up from peacetime duties. These types of vessels had performed similar duties in 14-18 and, with shallow draughts and ample deck space, were well suited to mechanical sweeping. Up to 37 would taken up in all, and by the end of ’39 they would comprise flotillas in Rosyth, North Shields, Dover, Greenock and Harwich.
German minelaying began on 3 September 1939 when U-Boats started laying mines off our East Coast ports and that day saw the war’s first mine casualty: a Danish trawler in the North Sea. By 4 September a group of 8 minesweeping trawlers were conducting exploratory Oropesa sweeping off the Humber – a stretch of water that would claim 22 minesweepers during the course of the conflict. Our first losses of WW2 occurred on 10 September when one of U-13’s mines claimed SS Magdepur (8000t) off Alderburgh, and the Collier SS Goodwood was sunk off Flamborough by a mine laid by U-15.
The loss of the SS Marwari near the Scarweather Light Vessel off Swansea on 3rd October provided an ominous warning that life was about to get even more dangerous. She was sunk in a channel that had been swept mechanically many times and, with the loss of another vessel in the same waters the following day, it was clear that the Germans were using magnetic mines. Although these had been used in the First World War, the Navy’s readiness to deal with them was minimal and the struggle to develop a counter to the new menace was the main focus of the minesweeping effort for the remainder of the year. Meanwhile, losses mounted and the RN’s first destroyer loss to a mine occurred on 13th November when HMS BLANCHE was sunk in the Thames Estuary whilst assisting HMS ADVENTURE which had also been the victim of a minestrike. Larger warships were also vulnerable; the cruiser HMS BELFAST was badly damaged in the Firth of Forth on 21st November and repairs would last over 2 years. This day also saw the loss of HMS GIPSY off Harwich with heavy loss of life), and the Battleship HMS NELSON was put out of action for 7 months after falling victim to a magnetic mine in Loch Ewe in early December. Minesweepers were also paying a price; HM Trawler (M/S) MASTIFF was sunk in the Thames Estuary Tongue LV on 20th November whilst trying to recover a magnetic mine – our first minesweeper casualty of WW2. Two days later, the Minesweeping Trawler was mined off Deal and had to be beached.
Although some rudimentary magnetic sweeps such as the well-named ‘Bosun’s Nightmare’ had achieved isolated successes over this period, during which 4-5 merchant vessels were being lost daily and the Port of London could barely be kept open, a real breakthrough needed the recovery and exploitation of a mine. This breakthrough arrived on 23 November when minewatchers at Shoeburyness observed aircraft-laid mines resting intact on the mudflats offshore. HMS VERNON - the RN’s Mine and Torpedo School – immediately sent teams to the location and, led by Lt Cdr Ouvry, two mines were successfully rendered safe the following day. Admiralty scientists would now be able to develop sweeps to counter the mines effectively, and these would steadily be introduced in the New Year.
For a day by day history of Minesweeping in WWII click here.
1940
As the RN entered 1940, Britain’s maritime lifeline was in danger of being cut off by the sinkings inflicted by the sea mine. Losses on the East Coast – and particularly in the Thames Estuary – had reached an unsustainable level, and a race was now on to develop a counter to the magnetic mine. Aided by the insights gained from Ouvry and Lewis’s dis-arming successes off Shoeburyness, three new sweeps were about to be trialled.
On 3 January 1940, HMS BORDE commenced sweep trials in Barrows Deep (Thames Estuary). An ex-Collier, she was classed as a ‘Mine Destructor Ship’ and fitted in the bows with a 450 ton electro-magnet which – it was hoped – would allow her to safely detonate magnetic mines as she approached. Her first success came on the 4th, with an explosion just 40 yards from her hull causing some minor damage, and 4 days later she bagged another 4 mines off the North Goodwin before returning to Chatham for badly-needed repairs. At the same time, a Wellington bomber aircraft commenced sweep trials at Boscombe Down with the DWI system: a 48ft diameter coil powered by a Ford car engine, and – more importantly in the longer term – HM Tugs SERVITOR and SALVOR commenced magnetic sweep trials off Shoeburyness with the towed, buoyant LL magnetic sweep.
Although the Mine Destructor Ships would play a useful role in confined waters over the next year, they were very limited tactically and could not be considered for the ‘Fleet operations’ that Fleet sweepers such as the ‘Halcyons’ and ‘Smokey Joes’ were intended. Furthermore, the loss of Destructor Ship HMS COBURN off Le Havre in May gave the German Navy an insight into their technology, leading to their effectiveness diminishing. Meanwhile, the DWI sweep fitted in the Wellington aircraft (usually flying in a formation of 3 aircraft to widen the swept path) depended on levels of navigational accuracy that could not be achieved by a fast moving aircraft, and therefore its operation was restricted to carefully defined waterways. Within these limitations, it achieved important success in aiding the safe evacuation of the Dutch Royal Family in May 1940, and in operations to keep the Suez Canal clear. For sustained, intensive minesweeping operations it was clear that the LL was the way forward and following early successes – and the fine tuning that was needed given the extensive damage inflicted on the trials vessels – the decision was taken in March 1940 to fit the LL on all sweepers capable of deploying it. Initial priority was the Thames Estuary and ‘first responders’ were the Trawlers of the 120th Minesweeping Group based at Sheerness and operating in and around the Knock Deep.
But the German mine offensive did not pause wait for these developments, and the early months of 1940 saw a significant burden being placed on underpowered HM Drifters and Trawlers towing the unwieldy Bosun’s Nightmare and – of course - continued sinkings; 90,000 tonnes of shipping in January alone. Examples of these losses included the 10,000 tonne Union Castle liner DUNBAR CASTLE - lost off the North Foreland on 9 January – and the destroyer HMS GRENVILLE; sunk in the Thames Estuary later that month. Life was also getting harder for the Fleet and Auxiliary sweepers above the waves, with the Luftwaffe increasingly targeting these vulnerable vessels. Losses stemming from this policy included the ’Halcyon’ HMS SPHINX and HMTs (M/S) FORT ROYAL & ROBERT BOWEN all bombed & sunk off the Scottish coast. However, by the end of April the minesweeping ‘bag’ in UK waters was 313 moored & 91 magnetic mines, for the loss of 133 ships totalling 425,00 tonnes.
As can be seen, the ‘Phoney War’ had never existed at sea, and it came to an end on land on 10 May 1940 when Germany invaded France and the Low Countries. As part of the offensive, mines were laid at Ijmuiden, the Scheldt, Flushing Roads, Zeebrugge, Ostend & off Dunkirk and, in response, the Admiralty despatched an assortment of LL Trawlers & mag sweep drifters from the Thames and Sheerness ‘forces’ to provide a counter. The Senior Officer for these operations was Cdr Peterson – Head of HMS VERNON’s LL Experimental Flotilla. Air attacks on the sweepers became a regular occurrence and Flushing – the initial operating base – swiftly became untenable as a result. HM Trawler ST MELANTE was bombed and damaged whilst alongside The Hook, the Skipper receiving a severe head wound and subsequently being made a POW when captured in a Dutch hospital. Minesweeping operations – including the clearing of a channel for the safe evacuation of the Dutch Royal Family onboard HMS HEREWARD - continued off the Dutch coast until 19th May 1940 withouut further loss, although HMT (M/S) RIFNESS was bombed & sunk off Ostend on the 20th. The Marine Nationale also took losses; the French auxiliary minesweepers FS Duquesne II & FS Henre Guegan were both lost to mines in the Scheldt. Along with the return of our minesweeping trawlers to Sheerness, a Dutch minesweeper contingent also made its way to the UK; HNLMS Jan van Gelder going on to serve with the 11th Minesweeping Flotilla based at Milford Haven and the 9th MSF at Portland.
Although minesweeping was not a feature of Operation DYNAMO– the withdrawal of the BEF from in and around Dunkirk (27 May – 4 June 1940) – minesweepers featured extensively in the rescue and it would be appropriate to record their service here. 36 minesweepers were involved, of which a number were sunk and many damaged. Sinkings included Paddle Sweepers BRIGHTON BELLE, GRACIE FIELDS, WAVERLEY, BRIGHTON QUEEN & DEVONIA and the ‘Halcyon’ SKIPJACK. Minesweeping Trawlers also suffered; OCEAN REWARD, THOMAS BARTLETT, POLLY JOHNSON, and ST ACHILLEUS were lost. However, the fact that the Sheerness Minesweeping Force of 8 Oropesa & 6 LL Trawlers, 4 LL Tugs, 6 Skid Drifters & 4 Magnetic Drifters was not committed to the evacuation highlights the continued importance and intensity of operations to keep the Thames Estuary open. The German occupation of France meant that minesweeping operations in UK waters became even more hazardous in the latter half of 1940, with an increasing number of sweepers sunk or damaged by air attack whilst trying to combat minefields that were being laid by ships, submarines and aircraft.
Three significant developments took place in the latter half of 1940 which would go on to influence the nature and intensity of the fight against the mine in the long term. Firstly, evidence emerged of mines being employed by enemy forces in the Mediterranean; the first ‘culprits’ being found in the paravanes of our cruisers bombarding Derna and Tobruk in July. The only vessels available to deal with these were two ‘Smokey Joes’ – HMS FERMOY and ABINGDON - based at Malta (the 3rd MSF to which they had belonged had left the Med at the beginning of the year to assist with the fight in UK waters). The focus for these two sweepers was upon the island itself, and their operations in the latter half of the year were aimed at combating the mine barrages laid around Malta by the Italian Navy.
The second development, which was to provide some measure of relief in 1942 for our scarce forces in the Med, was the arrival of (eventual) reinforcements in the shape of the new class of minesweepers: the ‘Bangors’. Although they were small, cramped and uncomfortable, 51 of these sweepers were commissioned for the RN over the next couple of years, with the first Bangor flotilla – the 9th - forming up at Scapa in the Winter of 40/41. Their size meant that magnetic sweeps could not be carried, and they were also limited in what acoustic sweep gear could be fitted when that technology was developed. However, although they were not designed for escort work they could be fitted with ASDIC and depth charge rails and went on to see valuable sweeping and escort service during hostilities despite being atrocious platforms in any significant sea state.
The third and final significant development was a series of steps in the technology race that was an intrinsic part of the mine warfare campaign. Already, in May 1940, Germany had introduced bi-polarity into its magnetic mines, necessitating a second sweep and therefore a doubling of the influence sweepers’ workload. Then, in August, mines in the Bristol Channel were observed detonating even though there had been no evidence of a ‘lay’. Suspicions over the introduction of arming delays & ship counts were then confirmed by Mine Destructor Ship HMS BUSHWOOD over a period of 4 days in Swansea Bay when 6 mines were swept in the same lap. This, again, would lengthen and complicate the sweeping mission. Finally, in October 1940, the acoustic mine appeared. These mines were first used in the Thames Estuary and RN suspicions were immediately raised by the fact that enemy aircraft had been observed to be switching off engines as they laid and that vessels operating at higher speeds were the ones falling victim. Rudimentary devices were initially used to sweep them – such as pipe noise makers towed astern of ships, but until these mines could be recovered and exploited the development of an effective counter was unlikely. Pending a solution, vessels inside the 20 fathom depth contour were advised to proceed at no greater than 9 kts – which may have rendered them safer against the mine but also left them more vulnerable to air and submarine attack!
In late October the recovery and exploitation of an acoustic mine – found ashore in the mouth of the River Ogmore near Porthcawl - allowed a more effective sweep to be developed. This was the Kango vibrating hammer – known as the ‘SA’ (Sweep Acoustic) that was being widely fitted before the end of the year and was to see significant success fitted either in the bows of a vessel or streamed outboard. The risks remained significant though; the minesweeping trawler RADNOR CASTLE had to be beached off Plymouth following a too-close detonation and in December HM Trawler COURTIER detonated 4 acoustics in swift succession, the last one breaking the legs of 4 crew members and putting the trawler in dock for several months. A less conventional minesweeper also incurred damage in late December 1940; the fast Isle of Man Steam Packet SS VICTORIA had already set off 8 or 9 mines during her transits back and forth to Liverpool, but on the 27th the detonation just off the Douglas Bar Light was a little too close and she had to be towed back to port although, in this instance, no casualties were reported.
Click here to learn more about enemy mining in 1939-40, the magnetic mine and magnetic sweeps.
For a day by day history of Minesweeping in WWII click here.
1941
1941 witnessed a further expansion in the number of theatres in which the mine threat loomed large during the Second World War. Shipping off the coasts of Australia and New Zealand would be lost to enemy mines, whilst a major commitment to the support of the Soviet Union (Russia) would see the RN’s sweepers spending a protracted – and highly dangerous - spell in Arctic waters. Meanwhile, the Royal Navy’s commitments in the Mediterranean would intensify. And throughout this period, Britain’s ports and coastline remained under a state of siege with Germany laying increasingly advanced mines in an effort to starve the country of supplies.
The mining of Australian and New Zealand waters actually began in late 1940 when German Raiders ORION and PINGUIN – merchant vessels converted and disguised to prey on Allied shipping – secretly laid mines off Auckland, W. Australia, the Bass Strait, Tasmania, Newcastle, Sydney & Melbourne. Similar lays took place off the South African coast in February 41. Although losses were not heavy, disruption to trade routes was significant whilst the nascent minesweeping forces of those countries steadily dealt with the threat. The South African minefields posed a particularly significant threat to convoy traffic using the Cape route, and badly-needed RN assets were diverted there to help cope.
The commitment to Russia would commence in August 1941 when HMS HALCYON, HARRIER & SALAMANDER provided part of the ocean escort for Operation DERVISH – the first convoy to North Russia. Once they’d arrived and been established in the White Sea, these ‘Halcyon’ class – and their sister ships that would arrive as reinforcements over the coming weeks and months – would follow an exacting routine; minesweeping in highly adverse weather conditions in between providing local escort for convoys just before their arrival at Murmansk or Archangel and just after their departure. This commitment lasted until late in 1943, and although the threats from mine, U Boat, air and surface attack would increase in 1942 and 1943, it is fair to say that the ‘early arrivals’ had the toughest time in terms of the bleak, bare conditions that they had to face, made worse by the fact that at this stage in the war none of them had been modified for Arctic conditions.
In the Mediterranean, Malta increasingly became the focus of German efforts to cut our sea lines of communication. The 3rd Minesweeping Flotilla, composed of the elderly, coal-burning ‘Aberdare/Hunt’ sweepers (more commonly referred to as ‘Smokey Joes’) came under increasing pressure to keep Grand Harbour and its approaches open for our larger warships based there and the convoys that sustained the island’s population. HMS HUNTLEY was bombed and sunk in January, a fate that also befell HMS FERMOY – damaged twice during air attacks in April and then finished off in another attack in May whilst still in dockyard hands. Meanwhile mines had badly damaged HMS ABINGDON and the Minesweeping Trawler HMT PLOUGHBOY. Such was the strain on the Fleet Sweepers in Malta that local naval authorities were hastily requisitioning trawlers and drifters to fit out as minesweepers, and these small auxiliaries bore the brunt of sweeping duties in the following months – operating at night to avoid incessant air attacks.
Further to the East, ‘Smokey Joes’ of the 2nd Minesweeping Flotilla were working hard to keep the main Fleet Base of Alexandria open, together with the North African coastal routes necessary for the support of the British Army in Egypt and Libya. The evacuation of Crete saw the loss of HMS WIDNES to the Luftwaffe, and HMS STOKE was lost off Torbruk in similar circumstances. The German Air Force also used the cover of bombing raids to lay mines off Alexandria and at either end of the Suez Canal. The mining of the Canal provided invaluable employment for the RAF’s Wellington bombers converted for magnetic minesweeping but elsewhere the burden fell heavily on the conventional sweepers. The threat posed by the mine was confirmed in tragic fashion towards the end of the year when the cruisers of ‘Force K’ ran into an Italian minefield off the North African coast. HMS NEPTUNE and destroyer HMS KANDAHAR were sunk; 736 of NEPTUNE’s crew of 737 losing their lives.
But no matter how important the commitments to the Mediterranean and North Russia, the country’s strategic priority remained the UK’s home waters, and it was here that Germany’s main, mining effort was focused. Up to 100 minelaying sorties were being flown each night by German aircraft – although this scale of effort dropped off after the invasion of Russia - and E-Boats (Schnellboote) were also increasingly involved. Hull, Swansea, Cardiff, Liverpool, the Humber and London were amongst the ports singled out for attention, and the whole of the East Coast remained vulnerable. The larger Fleet Sweepers such as the ‘Halcyons’ and ‘Smokey Joes’ continued to work flat out, but the coastal and inshore burden was increasingly being shouldered by the trawlers and drifters that had been requisitioned. The scale of the trawlers’ contribution can be gauged by the fact that, by the end of 1941, HM Trawler ROLLS ROYCE had alone accounted for over 100 mines. Some relief was at hand, however; the ‘Bangor’ class of small Fleet sweepers were starting to be delivered and the first of their flotillas – the 9th – became operational in the Spring. Their size, though, meant they were unsuited for the ‘LL’ magnetic sweep, but this shortcoming was counter-balanced by the arrival of increasing numbers of Motor Mine Sweeper (MMS) auxiliaries. These were cheap, simple hulls built of wood and based on a trawler design; they were capable of deploying a magnetic and acoustic sweep and – with over 400 built for the RN before the war’s end - became an invaluable part of the fight.
As ever, the technological battle continued; giving the conflict the atmosphere of a boxing match through its rhythm of punch and counter-punch. Following on from the introduction of the acoustic mine in 1940, Germany now introduced more sensitive settings to its influence mines, allowing magnetic and acoustic variants to be laid in deeper waters. Already - at the beginning of the year - ship-counts and arming delays had been introduced, and these developments resulted in greater areas of water having to be swept over longer periods of time. Finally, the Germans introduced combined acoustic-magnetic actuation systems to its ground mines, meaning that vessels in unswept waters were at risk from such mines even though their self-defensive measures such as magnetic degaussing were in operation.
For a day by day history of Minesweeping in WWII and what happened on this day in 1941 click here.
1942
The geographical spread of enemy minelaying that had been a feature of the battle in 1941 persisted throughout 1942 and, indeed, the remainder of World War 2. The minesweepers of the Royal Navy and Royal Naval Patrol Service remained at full stretch despite the arrival of new classes of sweepers, carrying out their inherently dangerous task in all weathers and frequently whilst under attack. The year witnessed important tactical developments, though; whereas previous efforts had purely been to keep our sea lines of communication open, 1942 saw the first developments in the use of minesweeping forces ahead of Allied amphibious assaults as strategic momentum start to shift (slightly) in favour of the Allies.
The routes around the Britain’s coast and the approaches to its ports remained the ‘Number 1’ priority. Minesweeping in our waters remained a 24/7 commitment; trawlers, drifters and auxiliary Motor Mine Sweepers operating off the ports and on the inshore routes, and the larger ‘Fleet’ Sweepers taking up the task in more exposed waters. The ‘Bangors’ had arrived just in time for this role, as the more capable ‘Halcyons’ were increasingly committed to the Arctic Convoys and operations in the White Sea and Kola Inlet (see later). The ‘Bangors’ also acted as a useful fire-brigade, and the year saw them being switched from area to area around our coast as circumstances dictated. The new 13th Minesweeping Flotilla was switched from Rosyth to the South Coast where it cleared coastal convoy routes in close proximity to German guns and aircraft, and was then rushed to the North West Approaches off W. Scotland and N. Ireland to ‘sweep in’ (in appalling weather conditions) the first convoy carrying American forces. Similarly, the sole ‘Smokey Joe’ flotilla in UK waters – the 4th – was chopped back and forth between the East Anglian Coast and the South West Approaches (based at Plymouth) to keep routes clear from both enemy mines and any of our own defensive mines that might have ‘strayed’. Meanwhile, small shipyards in America, Canada and the UK were providing reinforcements in the form of auxiliary minesweepers such as the wooden Motor Minesweepers (MMS), built of wood, cheap, and fully capable of influence (magnetic and acoustic) sweeping in coastal waters.
Losses, of course, continued. In just a few weeks spanning January & February, five requisitioned trawlers (HMTs LOCH ALSH, CAPE SPARTEL, CLOUGHTON WYKE, BOTANIC & WARLAND) were lost to air attack in the North Sea, whilst HMT IRVANA was sunk by mine and HMT UNCITY foundered in the same waters. Losses to the Fleet Sweepers in British waters included HMS SELKIRK (bombed) and HMS FITZROY (mined).
In terms of ‘assault sweeping’, the first use of this tactic in European waters by the RN took place during Operation JUBILEE – the raid on the port of Dieppe in August. Two flotillas of ‘Bangors’ were used to clear the approach channels for the Division-sized raiding force, and although no mines were encountered on the run in to the landing beaches, it proved a useful stepping stone in the evolution of tactics and procedures that would be used so effectively later in the war.
Further afield, the naval war in the Mediterranean intensified. Malta – a vital base – came increasingly under siege and the ‘Hunt’ class sweepers there came under intensifying air attack as they fought to overcome the growing number of mines being laid in local waters. HMS ABINGDON was bombed on several occasions before finally having her back broken whilst under repair in Grand Harbour, leaving the island without Fleet Minesweeper assets until the arrival of a convoy (Operation HARPOON) in mid-June. The escort force for this convoy included HMS HEBE & SPEEDY (‘Halcyons’) and HMS HYTHE & RYE (‘Hunts’) – these would go on to form the 17th Minesweeping Flotilla. They were badly needed; the two minesweeping trawlers that had been providing temporary cover were mined and sunk off the island in May, and the sweeping force was down to a gaggle of Motor Launches which had been converted to carry light sweeping gear for inshore work. The convoy and reinforcements arrived just in time, but HARPOON’s arrival itself highlighted how big the problem was; despite the 17thMSF sweeping ahead of the surviving ships, another merchant vessel was mined & lost, a Polish destroyer was sunk, and 2 others damaged. Meanwhile, the mines also claimed 2 minesweeping auxiliaries and damaged HEBE herself. Despite all this, on the day following its arrival, the Sweepers of the 17th MSF and the 3rd Motor Launch Flotilla were out ‘on task’; clearing around 50 mines from the harbour’s approaches in the coming weeks, and several hundred over the coming months. This provided a level of safety that allowed the 10th Submarine Flotilla to return to its Malta base. These sweepers would also play a vital role in getting the survivors of the vital PEDESTAL convoy (including the tanker SS OHIO) safely into port in mid-August.
Further to the East, the ‘Hunts’ of the 2nd Minesweeping Flotilla had been fighting to keep Alexandria and its approaches clear from enemy mines. German and Italian efforts had included further attempts to shut down the Suez Canal itself; resulting in its closure for 2 days in June before the Wellington DWI aircraft, trawlers and divers could clear all the mines. After the victory at El Alamein in November 1942, the Alexandria sweepers were able to extend their operations along the North African coast to allow the re-supply of the advancing 8th Army, and in this the 2nd MSF ‘Hunts’ were aided by the newly arrived ‘Bangors’ of the 14th Flotilla. These vessels: HMS CROMER, ROMNEY, CROMARY & POOLE had already seen action in the Indian Ocean; conducting assault sweeping ahead of the invading force in Operation IRONCLAD – the capture of Madagascar. This was the first such operation of this nature for minesweepers in the Second World War; pre-dating Operation JUBILEE (Dieppe) by 2 months. HMS CROMER would be lost to a mine off the Egyptian coast in November.
At the Western end of the Mediterranean, the TORCH landings on the North African coast witnessed the arrival and involvement of the 13th (Bangor) MSF and the 12th (Algerine) MSF. The large Algerines were built to a specific ‘wartime’ design and were capable of deploying all forms of minesweeping equipment in addition to having an anti-submarine capability, whereas the smaller Bangors were very cramped and unable to operate the LL magnetic sweeps. No mines were located off the TORCH beaches, but the operation marked the beginning of an intensive 3 years for the 12th, during which it led a number of amphibious assaults and swept over 2300 mines. Losses soon followed, though: whilst minesweeping a few weeks after the invasion HMS ALGERINE – name ship of the class - was torpedoed & sunk with heavy loss of life by an Italian submarine.
Throughout 1942, the commitment to support Russia (Soviet Union) placed a heavy burden on the ‘Halcyon’ class. The sweepers were progressively modified for service in Arctic waters, but were never anything less than uncomfortable and exposed in these hostile waters. The usual routine would be for the sweepers - based in the White Sea or at Murmansk subject to icing levels – to act as a local escort for 2 – 3 days for incoming or outgoing convoys, whilst conducting minesweeping operations in between convoys. New arrivals, or sweepers returning to UK for badly-needed maintenance, would do the whole journey in or out with the convoy. During QP 9, HMS SHARPSHOOTER rammed and sank U-655, but the dangers in local (Russian) waters were as great as they were on the open seas; the sweepers came under regular air attack off Murmansk and Archangel, with HMS HUSSAR lost to enemy bombers in June. HMS NIGER was lost in tragic circumstances in July when – lost in thick fog – she mistakenly led her ‘flock’ of merchant vessels into a British minefield off Iceland, and - in September - HMS LEDA was torpedoed and sunk to the west of Bear Island. A bloody year.
For a day by day history of Minesweeping in WWII and what happened on this day in 1942 click here.
1943
Nineteen Forty Two ended on a bitter note for the RN’s minesweeping force; HMS BRAMBLE lost on 31st December to the guns of the heavy cruiser HIPPER and her accompanying destroyers whilst defending an Arctic convoy. But the battle to defeat the mine had reached a turning point; although Germany, Italy and Japan would continue to mine our sea lines of communication in South East Asia, the Arctic, the Mediterranean and around the UK, our forces, tactics and equipment would prove equal to the challenge and - although the even greater U-Boat threat had yet to be mastered - the mine itself would not threaten again the direct security of this country.
The growing size of our minesweeping forces confirmed, though, the continued potency of the threat. By January 1943 over 30,000 regular and reservist personnel were serving in sweepers, and our ‘orbat’ included 7 Flotillas of ‘Fleet’ Sweepers in UK waters and another 7 in the Mediterranean. Supplementing these units were an increasing number of wooden Motor Minesweepers, auxiliary sweepers being delivered from American and Australian shipyards, Minesweeping Motor Launches and, of course, the trawlers and drifters that continued to be the backbone of our sweeping effort in UK waters. At the beginning of the year, over a 1000 RN vessels were allocated to the minesweeping role.
In the Mediterranean, the initial focus was to reinforce the successes of Operation TORCH and – to the East - the advance of the 8th Army; necessitating a constant effort to keep a shipping lane clear spanning the length of the North African shore. This vital task would prove costly for the sweepers; HMS ALARM was lost to air attack in January and HMS FANTOME to a mine in May. Meanwhile, a Motor Minesweeper and a Minesweeping Launch were lost to mines off the port of Bizerta. However, a swept channel from Gibraltar to Alexandria had been established by May 1943, after the toughest ‘nut’ – the Sicilian Channel – had finally been cleared despite enemy minefields having been further infested with obstructor and anti-sweeping devices designed to make the task much harder. Malta continued to be a running sore; German and Italian efforts to mine its approaches were incessant. Hard-pressed forces there were reinforced by a flotilla of the old ‘Smokey Joes’ at the beginning of the year. Almost 500 mines had been swept here by May, but sweeper losses continued, HMS SPEEDY badly damaged by a mine and HMS HEBE damaged by a near-miss from enemy bombers.
After the North African campaign had been concluded in May – coinciding with the opening of the Mediterranean swept channel – focus now turned to offensive operations against Sicily and then the Italian mainland. The sweepers led the way. For Operation HUSKY (the invasion of Sicily in July 1943) a mixture of RN and USN Fleet Sweepers – plus auxiliaries that would increasingly become part of the assault ‘package’ due to their ability to operate inshore – swept ahead of the invasion force despite high seas, shore gunfire and air attacks. The only mines located were off the American beaches, where 63 mines were swept. In September, for Operation AVALANCHE – the invasion of the Italian mainland at Salerno – the assault sweeping was supplemented by Motor Launches using their light sweeps to get right up to the beaches. Other innovations included American and British minesweeping forces being ‘mixed’, but although this proved a success the wider challenge of getting amphibious shipping to stay in swept water (and not obstruct the sweepers) remained a problem. Nonetheless, from a sweeping perspective the operation was a success, with a large number of mines being swept off the invasion beaches. The latter stages of the year in the Med, with efforts focussed on clearing channels along the Italian coastline, around Sicily, Corsica and Sardinia, witnessed the loss of HMS HEBE, HMS FELIXSTOWE, HMS CROMARTY and HMS CLACTON to mines - the latter on the 31st December. HMS HYTHE fell victim to a torpedo off the Algerian coast. The extent of the mine threat was further exemplified by the fact that the 12th Minesweeping Flotilla had – alone – swept over 700 mines in its first year in these waters.
Throughout 1943 a small flotilla of Halcyons continued to operate in Northern Russian waters, where HMS BRITOMART had a lucky escape when hit by 2 bombs which failed to detonate. Relations with shore authorities were invariably difficult, and provided little respite from the constant air attacks taking place; at one point the RN sweepers refused to provide an escort and sweeping service to Russian icebreakers until essential stores and mail were released to them! With planning for D-Day gaining in intensity, though, measures were now in hand to end this commitment which had been instrumental in safeguarding the delivery of over four million tonnes of supplies to our ally, including more than 7000 aircraft and 5000 tanks.
Even further afield, the allies’ switch to the offensive was also being mirrored in the Far East. Although Fleet Sweepers could not be spared for this region, an increasing number of BYMS and MMS were despatched to the Indian Ocean. These RN vessels usually deployed direct from the American shipyards where they were built and, due to their wooden hulls, were usually in need of urgent repair by the time they arrived. Basing and support were a major problem though, as Colombo and Trincomalee in Sri Lanka (then known as Ceylon) had very limited space available, and Mombasa on the Kenyan coast was too distant from the likely operating areas. As a compromise, a very basic site at Mandapam on the Indian coast was founded at the end of the year and named HMS BURONG.
In the Atlantic, the German Navy opened a new ‘front’ in its mining campaign in the early summer, with U Boats attempting to mine the approaches to Halifax (Canada), St John’s (Newfoundland) and New York & the Chesapeake Bay (USA). The Canadian mines were dealt with by local forces and BYMS and MMS vessels about to deploy to the UK. Although the Canadian ports and one of the routes into New York suffered temporary closure, the disruption of shipping was not significant.
Finally, the UK itself remained a prime target for mining. E-Boats laid fields off the East Coast in March and continued with ‘hit and run’ minelaying tactics throughout the year. Lyme Bay and Portland approaches were also extensively mined and – with the introduction of new acoustic mines and changed arming settings – the recovery and exploitation of enemy mines again became a significant priority. On 24th September 1943 no fewer than 25 E-Boats attacked shipping and laid mines in the Harwich approaches, a potent reminder that the minesweeping effort around our waters could not be relaxed.
For a Day by Day history of Minesweeping in WWII click here.
1944
Although the strategic ‘high point’ of the RN’s wartime minesweeping effort took place off Normandy in the Summer of 1944, it would be misleading – and unfair – to focus purely on Operations NEPTUNE and OVERLORD during this chapter of our history of minesweeping in the Second World War.
As indicated in the ‘1943’ account, our forces assigned to the Russian convoys were now being drawn down in preparation for momentous events in the Baie de Seine. However, this minesweeping and escort commitment – which had claimed four ‘Halcyon’ sweepers (lost to mine, bomb, torpedo and gunfire) – had been essential in keeping a key Ally in the war[1] through the delivery of over four million tonnes of supplies, including more than 7000 aircraft and 5000 tanks. The last ‘Halcyons’ to return to UK waters were HMS GLEANER & SEAGULL, arriving at Loch Ewe in March before re-joining the 1st Minesweeping Flotilla at Scapa prior to shifting south in preparation for D-Day. At the same time, and for the same reasons, the 18th Flotilla of ‘Algerines’ also ended its escort/sweeping commitment in support of the Arctic convoys on the Loch Ewe – Iceland – Loch Ewe run.
Although it was still the case that the top-end Fleet sweepers couldn’t be spared, in the Far East our auxiliary minesweeping forces were slowly increasing in number. HMS BURONG – a ‘bare bones’ base on the Indian coast - was formally commissioned in January and by May twenty sweepers (launches, trawlers, whalers and MMS) had been docked at this small facility. However, due to stores and supply shortages much of the maintenance was done by cannibalisation of other units, and the inevitable consequence of this was that the number of ‘runners’ was steadily decreasing. Sweepers from HMS BURONG were deploying forward to the Burmese (modern Myanmar) coast in support of the 14th Army fighting there, and would remain extremely hard-pressed until 1945 when Fleet sweepers (starting with the 7th Flotilla) started to arrive from the UK and the (then) Royal Indian Navy was able to generate a flotilla of ‘Bathurst’ class corvettes with a minesweeping capability.
The Mediterranean remained a highly active theatre in which the mine – and its defeat – was a major factor in ensuring the security of our sea lines of communication and our armies’ ability to use the sea flank to defeat German forces. Clearance of the Strait of Bonifacio between Corsica and Sardinia was an ongoing priority for the ‘Algerines’ of the 12th and 19th Flotillas and the ‘Bangors’ of the 13th (which had lost HMS CROMARTY to a mine in these waters in October 1943) in the first half of the year, and over 400 mines had been swept here by the time the mission was concluded in May 1944. Interrupting this effort, Operation SHINGLE saw the Fleet Sweepers (and a growing contingent of Motor Launches, Motor Minesweepers and other auxiliaries such as ‘Yard’ sweepers) supporting the amphibious landings at Anzio in late January. Few mines were located ahead of the initial assault, which was hampered primarily by the sweepers having insufficient space allocated to them, but in the weeks that followed they came under heavy and regular attack from German aircraft – which were also laying mines – and from heavy guns ashore which were firing upon them at a range of almost 10 miles. One casualty during this period was HMS CIRCE; badly damaged when a mine was trapped in her sweep gear and detonated on the stern. Similar challenges from air and ashore faced the sweepers when clearing the Naval Gunfire Support boxes for the heavy units that would be firing in support of Allied forces during the 4th Battle of Cassino in May.
Between Anzio and Cassino, and during the subsequent Allied advance along the length of Italy during 1944, the sweeping effort focused – with just one major interruption – upon clearing shipping lanes between Naples and Livorno. This operation (Operation LOBSTER) saw hundreds of mines being swept despite innumerable obstructors and anti-sweeper devices being encountered. In August alone, RN and USN vessels swept 880 mines in these waters. The latter half of the year also witnessed extensive activity in Greek waters; Operation MANNA saw a number of flotillas clearing channels in the Adriatic and the approaches to Piraeus (Athens), and during these operations the newly-arrived 5th (Algerine) Flotilla lost HMS CLINTON and LARNE to mines. From the 12th Flotilla, HMS MUTINE & ESPIEGLE both suffered damage from mines that were set to explode on being cut and reaching the surface.
The major interruption to the work on the sea lines of communication arose from the invasion of Southern France (Operation DRAGOON) in August 1944. On this occasion, American MCM forces were in the preponderance as British units were still heavily committed to Operation NEPTUNE/OVERLORD off Normandy (see below). The newly arrived 5th (Algerine) Flotilla, plus the 13th (Bangor) and 19th (Algerine) Flotillas all participated, and HMS LARNE (whose loss is mentioned above) gained the distinction of being the only Algerine sweeper present at both the Normandy and St. Tropez landings. The flotillas experienced very different conditions during the assault and follow-up; the 19th reported a relatively quiet operation, whereas the 5th and 13th Flotillas both found themselves operating under heavy shore fire which sank two accompanying Motor Launches. Such was their proximity to the German defences, the 5th Flotilla fired almost two hundred 4”shells at shore targets. Overall, in an operation that hastened the collapse of German forces in occupied France, MCM forces accounted for 800 mines during the assault and aftermath, for the loss of 4 auxiliary units.
Operation NEPTUNE
Operation NEPTUNE was the codename given to the amphibious assault and securing of a lodgement on the French coast at Normandy. It was the maritime (and main) component of the better-known Operation OVERLORD, and our sweepers were fundamental to its success. Given that this was the largest amphibious operation in history, it is inevitable that it also involved the largest mine countermeasures effort in history, with the Royal Navy providing the great majority of these forces. Seventy six of 98 Fleet sweepers were RN units, and 33 of the 56 smaller ‘coastal’ sweepers. Seven RN Motor Minesweeper Flotillas were also present, along with a host of trawlers and motor launches. The mine threat was very significant; it posed the greatest menace to the invasion force and was the greatest single cause of loss to our ships on D-Day (6th June 1944) and during the long weeks that followed. The American Naval Commander of the Western Task Force – Rear Admiral Alan Kirk USN – stated in his subsequent report: “It can be said without fear of contradiction that minesweeping was the keystone in the arch of this operation. All of the waters were suitable for mining, and plans of unprecedented complexity were required. The performance of the minesweepers can only be described as magnificent”. It is impossible to give a full account of the minesweepers’ contribution here – a more comprehensive online account, together with a wider-ranging history of minewarfare, can be found on the MCD Officers’ Asociation website. However, a short precis of the operation will be attempted. ……..
Planning for Operation NEPTUNE has started as far back as 1942 and the requirement for a minesweeping force had always been present. The raid on Dieppe (Operation JUBILEE) had incorporated sweepers, and lessons from that (failed) mission and the series of assaults in the Mediterranean in ‘42, ‘43 and early ’44 had confirmed how essential sweepers would be, and how they could best be used for the assault itself and during subsequent fighting ashore. Training and exercises started at the beginning of the year (1944) just after the size of the force had been increased from six assault flotillas to ten in order to accommodate General Montgomery’s insistence on expanding the initial assault area from three beaches to five. This meant that additional flotillas had to be readied, and the 31st (Canadian) Minesweeping Flotilla had to undergo a very swift work-up as it had spent much of its war as an escort force, with sweep gear left on land. The pace and complexity of exercises intensified in the final months before D-Day, as did German minelaying efforts, and HMS ELGIN & HMS STORMCLOUD were both severely damaged in the weeks just before the big day, the former to the extent that it was declared a loss.
The minesweepers’ tactics broadly followed those that had been developed in the Med. On the night of the 5th/6th June, the Fleet sweepers – led by Motor Launches using light gear to sweep the shallowest mines that posed a threat to the sweepers themselves – would sweep ten separate channels to the five assault beaches for the amphibious ships to follow. Once they’d reached as far inshore as possible, the larger sweepers would break off to start clearing ‘boxes’ for battleships and cruisers firing in support of the landings, and then move on to widening the deep-water channels for follow-on shipping. The Motor Launches would continue to clear as close to the beach as they could get for the smaller boat traffic such as landing craft, whilst Motor Minesweepers and ‘Yards’ would start influence sweeping in the inshore waters. At the waters’ edge itself, 120 swimmers and divers of the Landing Craft Obstruction Clearance Units were performing the inherently dangerous task of blowing a path clear for the landing craft coming in on a flood tide. This was by day. At night, the sweepers would move to the flanks of the beachhead to counter any attack by surface craft and submarines. The 24/7 nature of these operations – sweeping all day and then actively patrolling all night – proved an exhausting routine for these small vessels and their hard-pressed crews.
A number of mines were encountered during the initial assault, but the only loss to the minesweeping force was USS OSPREY, part of the Western Task Force. Two RN sweepers had their gear fouled by mines and had to steam into unswept waters in order to clear them (they were under strict orders not to sink in the channel itself) but both survived the encounter. Most importantly, though, none of the shipping that carried the 130,000 American, British and Canadian soldiers that landed on the beaches of Normandy on the 6th June suffered loss.
In the days and weeks that followed the invasion, the mine proved the most effective German response to the Allies’ build-up, with the Luftwaffe launching minelaying sorties every night. This threat was magnified by the fact that the Germans were using a new type of mine – one with a pressure actuation system – that had been kept in reserve specifically as a counter to the invasion. We had no effective counter to this mine, and its presence – real or assumed – significantly slowed down the allies’ rate of build-up ashore. These, and other types of mine, caused a steady attrition of our forces. Victims included landing ships and freighters, the cruiser HMS SCYLLA – flagship of the Eastern Task Force - a number of destroyers, and the minesweepers HMS PERSIAN, HMS CHAMOIS, HMS VESTAL, HMS GLEANER & HMS FRIENDSHIP. The high casualty rate for sweepers was partly because German acoustic mines had now been set to ‘target’ such vessels, but the sweepers were also vulnerable to other forms of attack: HMS MAGIC & HMS CATO (both sunk by human torpedo), HMS PYLADES (midget submarine attack) and HMS LOYALTY (U-Boat attack). Finally, in a tragic ‘blue on blue’ caused by staffing errors, the ‘Halcyon’s HMS BRITOMART & HMS HUSSAR were sunk by RAF fighter-bombers, an attack that also left HMS SALAMANDER damaged beyond repair.
As the Allies gradually expanded their hold on Normandy and – eventually - broke out, the minesweepers steadily shifted their area of operations to clear the approaches to the vital ports that were being liberated. This saw our sweepers - particularly the MMS and BYMS flotillas with their better inshore capability - working off Cherbourg, Brest, Le Havre and Ostend. Their efforts inshore were supplemented in the harbours and docks themselves by the ‘P Parties’ – diving teams trained to locate and make safe or destroy the innumerable mines and booby traps left in the docks and wharves. This task proved particularly difficult in the huge port of Antwerp, where P Parties were diving even as V2 rockets were exploding in the adjacent docks.
The approaches to Antwerp – the Scheldt Estuary – provided the location for another massive minesweeping effort in 1944. Without use of the port, the swift advances of the Allies had stalled due to inadequate logistic support, and although the port itself had been captured, its approaches were still controlled by the Germans. After the Fleet sweepers had cleared channels for the bloody assault on the island of Walcheren in November, an assortment of auxiliary minesweepers – often operating under fire from ashore, which inflicted damage - took 22 days to clear the lengthy estuary from the sea to the port itself. Vessels in the 11 Flotillas included BYMS, MMS, Motor Launches, Minesweeping Trawlers, requisitioned fishing vessels (equipped with magnetic sweeps) and Landing Craft (also equipped with sweeps). For the loss of one BYMS and one ML, 267 mines were swept during the operation, and although losses continued in the weeks that followed, the port was functioning just in time for resupply of our armies fighting in the Battle of the Bulge and for the final assault on Germany itself. A fuller account of this vital operation can be found at http://wildfire3.com/sweeping-the-scheldt.html . See also this YouTube account of Operation CALENDAR. Although it was on a slightly smaller scale than NEPTUNE, the Scheldt clearance was of unprecedented tactical complexity and, equally, served an essential strategic purpose. Other losses over this period included HMS HYDRA; mined off Ostend and declared a Constructive Total Loss.
Although the minesweepers would continue hard at work in European waters in 1945, the focus would steadily shift to the Far East…….
[1] The scale of the Soviet Union’s sacrifice and achievements continues to be neglected in our understanding of WW2. It suffered around 27 million deaths (of which around 10 million were military), but inflicted no less than 80% of the German Army’s total casualties (4 million killed) in that war.
For a Day by Day history of Minesweeping in WWII click here.
1945
Although major amphibious operations – and the sweeping effort that enabled them – were not a major feature of the war’s final year, the mine remained a potent threat which meant that the RN’s minesweepers (now numbering around 1300 vessels, including auxiliaries) remained to the fore in guaranteeing the security of our sea lines of communication.
In UK waters more and more of the ‘Algerines’ were coming ‘online’; the 8th Minesweeping Flotilla had commenced operations in the Med towards the end of ’44, and the 10th and 11th Flotillas would be formed in ’45. This, together with a steady flow of MMS and – from American yards - BYMS auxiliaries, allowed many of our requisitioned trawlers to revert to their peacetime role and help feed the nation. Their efforts had been immense; Minesweeping Trawlers had suffered a 20% loss rate in their efforts to keep home waters clear, and their sacrifice is often overlooked. Crewed by members of the Royal Naval Patrol Service (RNPS), and known affectionately as ‘Harry Tate’s Navy’, their contribution can be witnessed at the RNPS Museum at Sparrow’s Nest, Lowestoft and their nearby Memorial; which records the 2397 sailors who were lost at sea and whose bodies were never recovered. The Association’s website is at: www.rnpsa.co.uk/cms/
Although the “flotilla” remained the basic tactical grouping for the sweepers (apart from trawlers, which were deemed to be only worthy of “groups”!), the final months of the war in NE Europe witnessed the creation of some larger formations to deal with the contested sea areas in which E-Boats and midget submarines were still actively minelaying. The formations, comprising flotillas of Fleet and auxiliary sweepers, were labelled “Force A”, “B”, “C” and “D”, dealing with (respectively): Dutch waters and coastline; Dutch inland waters, including the Scheldt; German waters off Heligoland, Cuxhaven, Bremerhaven & Hamburg, and Norwegian coastal waters including approaches to Oslo, Trondheim, Bergen, Stavanger & S. Kristiansund. Sadly, these Forces didn’t include any ‘Smokey Joes’; the final vessels of this class – built in the closing stages of the First World War and in action again from the 3rd September 1939 – were paid off in the latter stages of 1944. Their swansong had been the 4th Flotilla’s efforts on D-Day and its aftermath: sweeping in the US 1st and 29th Infantry Divisions to OMAHA Beach.
In February 1945 the ‘Algerines’ of the 10th Flotilla were sweeping off Stavanger, Norway to allow Escort Carriers to launch anti-shipping strikes and conduct minelays in those waters. These sweepers returned from this Operation (codenamed SHRED) to conduct mine clearance off the UK’s East Coast and in Dutch and Belgian waters alongside the 18th Flotilla. HMS READY suffered damage from an acoustic mine during these final stages of the war, and tactical/technological problems were still being posed, with the final types of magnetic mine being configured such that the LL sweep – which had been instrumental in defeating that threat since 1940 – was proving worryingly ineffective.
In the Mediterranean, the slow, dangerous work of clearing tens of thousands of mines from the major shipping routes continued. Attacks on our sweepers had virtually ceased, but the mines continued to provide enough of a threat to keep the sweepers’ crews on their toes. January 1945 witnessed the 12th and 5th Flotillas sweeping the Dardanelles to allow safe passage for the US Delegation’s support shipping for the Yalta Conference. This operation ‘bagged’ 120 mines and concluded with 11 ‘Algerines’ of the two flotillas linked abreast in a final team sweep of the swept channel.
Elsewhere in the Mediterranean, the 19th Flotilla were engaged in Operation ANTAGONIZE; sweeping between Ancona and Zara off Italy’s Adriatic coast. During this operation, HMS ANTARES struck 2 mines and was badly damaged, but – as ever – the flotilla continued its work, sweeping off the Yugoslavian coast (Dubrovnik), Taranto and then up to Venice and Trieste (where they were joined by the 8th and 5th Flotillas) before VE Day. Losses continued; Motor Launch 558 and Danlayer CORIOLANUS – both supporting the Fleet Sweepers – were lost to mines in the final week of the war in Europe. Prior to ANTAGONIZE the 8th had been sweeping the densely mined Corfu Channel; coping with anti-sweeper and anti-sweep mines which took a heavy toll of sweep gear and - on 12th January – claimed HMS REGULUS; sunk when a mine exploded on the stern during recovery of the sweeps. Almost 150 mines were swept during this effort. Meanwhile, the 12th Minesweeping Flotilla - the first of the ‘Algerine’ flotillas – followed up its Dardanelles work by sweeping 187 mines off Euboea and 130 off Kinaros in the Aegean Sea, finishing the war at Genoa by way of Livorno.
Still further afield, the Royal Navy was now (finally) able to deploy more substantial minesweeping forces to the Far East, where the burden thus far had fallen upon a motley collection of BYMS, MMS, trawlers, drifters, launches and whalers. Despite the challenges they had faced, though, these vessels had been hard at work and in January 1945 six of the BYMS had participated in Operation LIGHTNING, the capture of Akyab Island off the Burmese (Myanmar) coast by 3 Commando Brigade. But despite this success, reinforcements were needed, and in January 1945 the 6th and 7th Flotillas (Algerines) at Portsmouth and Plymouth were told to make ready for foreign service. Preparations including vessels swapping across flotillas to ensure commonality of equipment (particularly for propulsion, where some vessels were steam-turbine driven whereas others had reciprocating steam engines). The 7th started deploying to the Far East in February, and HMS RECRUIT and PINCHER claimed the only Algerines’ U-Boat kill of the war when – en route to Gibraltar - they caught a damaged U-300 on the surface and sank it. HMS SQUIRREL’s deployment was delayed when she damaged her bows in the Bay of Biscay whilst trying to put a salvage party onto a foundering Floating Dock that was being towed to Gib.
The 6th Flotilla started its deployment in early April, just as the 7th was arriving in Colombo, Sri Lanka. The first part of its transit (UK – Gibraltar) was less exciting than that experienced by its sister flotilla, but in an inconclusive anti-submarine action HMS POSTILLION suffered slight damage from being a little too close to exploding depth charges. Meanwhile, the 7th Flotilla had departed Colombo and, despite having had minimal time for maintenance and further training, was heading to Rangoon, Burma (now Yangon, Myanmar) for Operation BROOM; the assault minesweeping element of the larger Operation DRACULA – the seizure of Rangoon by amphibious assault. The seizure of Rangoon – planned for 1st May 1945 - was vital for the logistic support of General Slim’s 14th Army, and was made even more important by the imminent arrival of the seasonal monsoon which would severely curtail road transport and aerial re-supply. Fortunately, the Japanese withdrew from Rangoon before DRACULA, and so the amphibious assault to land the 26th (Indian) Division was unopposed. Nevertheless, the 7th Minesweeping Flotilla – working alongside ‘Bangors’ and ‘Bathurst’ sweeper-corvettes of the Royal Indian Navy’s 37th Flotilla – had to clear the approaches to the port and city before the landing craft could go in. No mines were found to seaward, but the river yielded 23 detonations from Allied ground mines that had been laid previously. Notwithstanding mine damage to three landing craft, the minesweeping task had been completed by 3rd May.
Following DRACULA, our sweepers – including the newly arrived 6th Flotilla – spent several weeks conducting convoy escort and patrol duties, but the minesweeping task would come to the fore once more in July. At the beginning of that month, the 6th Flotilla took part in Operation COLLIE, sweeping 167 mines off the Nicobar Islands in the Andaman Sea in support of escort carrier strikes and shelling of targets by the 5th Cruiser Squadron. This was a precursor to Operation ZIPPER, which was to have been the invasion of Malaysia (now Malaya) scheduled for early September but cancelled after Japan’s surrender.
Towards the end of July, the last significant minesweeping operation of the war took place – with tragic consequences for the 7th Minesweeping Flotilla. Operation LIVERY’s main mission was to conduct air strikes on Northern Malaysia and Phuket Island, Thailand, but Japanese mines littered the operational area and so - accompanied by RIN ‘Bathursts’ PUNJAB and DECCAN - the 7th conducted sweeping off Phuket Island in support of a Task Force comprising the battleship HMS NELSON, escort carriers HMS EMPRESS and AMEER and various cruisers & destroyers. On 24th July, 11 mines having already been swept, HMS SQUIRREL hit a mine just seconds after the leading vessel’s sweep-wire (behind which SQUIRREL was ‘tucked’) had been destroyed. Despite efforts to save her, SQUIRREL had to be abandoned and was then sunk by gunfire from accompanying destroyers. Seven sailors perished in this incident, but worse was to follow two days later when the Flotilla had resumed its operations. A further 24 mines had been swept when the force came under repeated kamikaze attack. The sweepers were unable to manoeuvre due to sweeps being deployed, and during the late afternoon’s attacks on 26th July HMS VESTAL was struck amidships. The damage inflicted by the kamikaze was such that the ship could not be saved and, as with her sister ship two days earlier, HMS VESTAL had to be sunk by destroyer gunfire. 20 crew members perished in this attack.
Operation LIVERY was the last significant sweeping operation of the Second World War, and HMS VESTAL was the last ‘major’ RN warship to be lost in that conflict.
CONCLUSIOn
The epic achievements of RN minesweepers in World War 2 can be viewed through a number of ‘prisms’. Firstly, there is the classic maritime strategy perspective; sweepers attempting to overcome the sea mine – a classic ‘sea denial’[1] weapon - in order to maintain the ‘sea control’ that would allow the safe passage of our merchant vessels and heavy naval units. Then – having helped maintain sea control – facilitating ‘power projection’ at the tip of the spear in a number of amphibious assaults, culminating in Operation NEPTUNE and the Scheldt operations. Or, we can view the struggle from a technological perspective; looking at the cut and thrust of measure and countermeasure; starting with the arrival of the magnetic mine, the introduction of the acoustic mine, the various ‘tunes’ that could be played with mine settings (including the specific targeting of the sweepers) and, in the summer of 1944, the introduction of unsweepable pressure mines. This viewpoint would link closely with a tactical ‘take’ – looking at how tactics evolved to employ the new technologies and, on a separate strand, how assault sweeping tactics were developed on the back of a series of increasingly demanding operations such as TORCH, HUSKY, AVALANCHE and SHINGLE. Alternatively, we could consider minesweeping in the context of the broad shift of the war as experienced by Britain; a period on the defensive followed by an inexorable shift to the offensive. And finally, we could look at these heroics with an eye to the RN’s post-1945 experience; where the mine has been a significant threat in the Falklands, the Gulf, the Red Sea and the Suez Canal. Of particular note here; the fight – and the tactical & technological ingenuity - to get Allied shipping into Umm Qasr in 2003 bears uncanny resemblance to the efforts to unlock the Scheldt in 1944 ……
But stepping back from a detached, academic assessment, we owe it to those who served to return to the harsh reality of the minesweepers’ battle in the Second World War. By V-J Day on 15 August 1945, RN minesweepers had cleared over 20,000 mines in almost 6 years of ceaseless effort - whilst under near-constant threat from above, on and below the waves. The minesweeping force, which had started hostilities comprising just 36 Fleet Sweepers and 40 trawlers, now stood at around 250 Fleet Sweepers, 307 Motor Minesweepers (MMS), 136 British ‘Yard’ Minesweepers (BYMS), almost 250 trawlers, drifters & whalers, and dozens of Motor Launches. They had paid a high price for their successes; 45 Fleet Sweepers had been lost, together with 10 Paddle Sweepers, 3 Mine Destructor Ships, 34 MMS, 6 BYMS, no fewer than 223 trawlers and 22 other auxiliaries. Mines had claimed over a million tons of British shipping but, crucially, had never stopped access to our ports being maintained. Nor had they prevented the massive amphibious invasions that were key to the Western Allies’ strategy. It had been a close-run thing though. Over the period when others might have been benefitting from the ‘Phoney War’ phase of hostilities (September 1939 – April 1940), the sweepers were fighting hard to staunch the ‘bleed’ to our shipping arteries caused by the magnetic mine. Over 4 years later, the use of a series of ad hoc measures to counter the unsweepable pressure mines had allowed our sweepers – at heavy cost – to do just enough to permit Allied forces to build up in Normandy to a level and tempo that allowed them to defeat German counter-attacks and then break-out from Normandy.
And the threat posed by the mine did not end with the cessation of hostilities. Around 500,000 had been laid by the various belligerents and efforts to sweep them would continue for many years. Just 24 hours after V-E Day, the ‘Algerine’ HMS PROMPT was mined off Ostend, and four years later - in 1949 - the Dutch cross-channel steamer PRINSES ASTRID was sunk by an unswept mine outside Dunkirk harbour. Today, for the Royal Navy’s Diving Teams and Mine Countermeasures Vessels, disposal of such ordnance – often found in trawler nets – remains a common occurrence, and as recently as 2018, WW2 mines were being found on an almost weekly basis during work to widen the main channel ahead of aircraft carrier HMS QUEEN ELIZABETH’s arrival in Portsmouth.
Finally, recognition from the highest level of the minesweepers’ effort, sacrifice and success should be set out here:
MESSAGE FROM THE PRIME MINISTER TO THE OFFICERS AND MEN
OF THE MINESWEEPING FLOTILLAS
Now that Nazi Germany has been defeated I wish to send you all on behalf of His Majesty’s Government a message of thanks and gratitude.
The work you do is hard and dangerous. You rarely get and never seek publicity; your only concern is to do your job, and you have done it nobly. You have sailed in many seas and all weathers …. This work could not be done without loss, and we mourn all who have died and over 250 ships lost on duty.
No work has been more vital than yours; no work has been better done. The ports were kept open and Britain breathed. The Nation is once again proud of you.
W S Churchill
[1] Often referred to as ‘Anti-Access, Area Denial’ (A2AD) in contemporary debate.
For a Day by Day history of Minesweeping in WWII click here.
This account of RN minesweeping in the Second World War is dedicated to my late father-in-law Leslie Frank Clarke (SSX 32433, HMS ROMNEY, ‘Bangor’ class, 1940 - 42) and his brother Albert Arthur Clarke (P/JX 325707, KIA 13 November 1943, destroyer HMS DULVERTON).
SOURCES
Barnett, Correlli. Engage the Enemy More Closely. (Sevenoaks, Hodder & Stoughton, 1991).
Brookes, Ewart. The Gates of Hell. (London, Arrow Books Ltd, 1973 edn).
Edwards, Kenneth. Operation Neptune – The Normandy Landings. (Fonthill, 2013 edn).
Elliott, Peter. Allied Minesweeping in World War 2. (Cambridge, Patrick Stephens, 1979).
Grove, Eric (Editor). The Defeat of the Enemy Attack on Shipping 1939 – 1945. (London & New York, Routledge, 1997).
Hardy, Hilbert. The Minesweepers’ Victory. (Weybridge, Keydex, 1976).
Hoole RN, Lt Cdr Rob and Bruhn USN, Cdr David D. Enemy Waters. (Berwyn Heights, Heritage Books Ltd, 2019).
Lund, Paul and Ludlam, Harry. Out Sweeps. (London, Foulsham & Co. Ltd, 1978).
Lund, Paul and Ludlam, Harry. Trawlers Go To War. (London, New English Library, 1972).
Robinson, Stephen. False Flags: Disguised German Raiders of World War II. (Exisle Publishing, Wollombi, 2016).
Rohwer, J and Hummelchen G. Chronology of the War at Sea 1939 – 1945 Vols I & II (translated by Masters, Derek). (London, Ian Allan, 1972).
Roskill DSC RN, Captain S W. The War at Sea Vols I – III. (Uckfield, The Naval & Military Press Ltd, 2004 edn).
Schofield, Vice Admiral B B. Operation Neptune – The Inside Story. (Barnsley, Pen & Sword Military, 2008 edn).
Williams, Jack. Fleet Sweepers at War. (Blackpool; J.F. Williams [Oropesa], 1997).
Williams, Jack. The Algerines. (Blackpool; J F Williams [Oropesa], 1995).
In addition to the books listed above, I have leaned heavily upon the following online resources:
https://www.naval-history.net/ Encyclopaedic detail on the RN in WW1 and WW2, including over 1000 individual ship histories.
http://www.minesweepers.org.uk/ Website of the Algerines Association. Ship & Flotilla histories, plus minesweeping tactics/equipment.
http://www.halcyon-class.co.uk/ Outstanding site giving detailed histories of each vessel in this class.
http://www.mcdoa.org.uk/MCD_History_Frames.htm Website of the Minewarfare & Clearance Diving Officers’ Association. Comprehensive overview of RN Minewarfare and Diving history and operations.
http://www.wildfire3.com/wildfire.html Detailed information on minesweeping operations off the East Coast and Thames Estuary.
http://www.rnpsa.co.uk/cms/ Information on the Royal Naval Patrol Service.
https://en.wikipedia.org/wiki/List_of_shipwrecks_in_March_1940 Handy resource listing ships lost on every day of WW2.
http://www.harwichanddovercourt.co.uk/warships/minesweepers/ Useful resource on minesweepers and naval operations in the Southern North Sea and Thames Estuary.
https://wrecksite.eu/wrecksite.aspx Very good site offering significant detail on all ships sunk and located.
https://uboat.net/ Site dedicated to German U-Boat operations, but contains surprising amount of information on their opponents.
Nick Stanley
Commodore, Royal Navy (Retd)
Copyright © 2018 Nick Stanley. All rights reserved.
To read about Minesweeping in WWII on this day in 1940 click here.
Find out about modern Minesweepers, Mine Hunters, Diving Teams and ongoing operations here.
NAVAL MINING AND MINE COUNTERMEASURES IN THE EUROPEAN THEATRE - AN alternative overview of wwii
Extracts from “Naval Minewarfare: Politics to Practicalities” by Captain Chris O’Flaherty, Royal Navy. Abridged and very slightly amended by Geoff Goodwin. (The writing of this publication was partially funded by the Guy Hudson Memorial Trust)
Mirroring the events of World War I, mining and the associated mine countermeasures battles commenced playing their significant part in naval battle from World War II's first day. Before the sun had set after the expiration on 3 September 1939 of Britain’s ultimatum to Germany, HMS Plover had commenced laying a defensive minefield off Bass Rock in the Firth of Forth.
The official analysis of British mining operations between 1939 and 1945 states that the British plus Allies in areas under British control laid: 159,992 defensive mines (a total that includes the 92,083 protective mines of the Northern Barrage between the UK and Iceland, and mines laid in the Mediterranean and Far East); 26,546 mines in ‘deep trap’ minefields (optimised to ensnare dived submarines, whilst allowing surface traffic to flow); and 77,312 offensive mines, plus 414 sweep obstructers. Opining that ‘The moored mine was the junior partner in the British mining offensive . . . they nevertheless served a useful purpose, in claiming a number of casualties and by forcing the enemy to devote a considerable effort specifically to moored-mine defence, often far from base.’ After alluding to the mine-and-counter-mine contest that saw influence ground mines laid, sink ships, recovered by the enemy, analysed, countered, swept by the enemy then improved by our own scientists and re-laid, etc., it went on to contrast the results of mining compared with other forms of naval attack.
Using analysis based on the apparently accurate statistics allowed by post-war reconstruction in the north-west Europe theatre of naval war, and citing errors of less than 1 per cent, it concluded that ‘mining was the most successful form of attack used in this important area of operations – a significant fact in view of its economy and its cumulative effect on the whole German war machine.’
Of the many mining campaigns conducted throughout the war, the German mine battle in May to July 1944 off northern France stands out as one of the biggest missed opportunities to deliver operational success. Whilst a British offensive minelay commencing 17 April 1944, known as Operation MAPLE, had used recently developed sterilisation clocks to ensure 4,000 air-laid mines and 3,000 surface laid mines would all be rendered harmless before the D-Day landings in June, the Germans had also refreshed their channel minefields but with a sterilisation date of late May 1944 applied to many mines. Both sides wished to maximise disruption to their enemy’s maritime mobility, whilst knowing for themselves when the mined waters would again be safe for the transit of friendly shipping. The British mining plan worked near to perfection,[1] with many vessels en route to the D-Day landings sailing over freshly sterilised minefields, screened by still active minefields that one by one sterilised over the following few weeks whilst the front expanded. The German mine sterilisation probably also saved many hundreds of British and Allied lives, augmented by the incredible work of British and American minesweepers.
With the threat of potentially thousands of mines throughout the English Channel and in the landing areas, 306 minesweepers were dedicated to mine countermeasures in support of the amphibious operation. In the week before D-Day, a large circle was cleared of mines just south of the Isle of Wight, with missions cautiously expanding southwards towards France. On the night of 5/6 June the sweepers carved routes right across the Channel to the beaches, where the landing force established the Allied foothold ashore. As part of Operation OVERLORD, MCM forces created and maintained ten main swept channels between Britain and France, expanding these to form assault areas off the beaches and then logistic support areas further offshore.
Now on the back foot, with Allied troops ashore in Europe and his previous minefields largely self-sterilised, Hitler unleashed his ‘secret weapon’ – the Oyster mine.[2] Both sides had developed unsweepable pressure-mine technology in 1943,[3] but both sides had kept it in reserve lest the enemy got hold of it and turned it against them. Now was the moment, and 400 of these novel mines were released from an underground storage site at Le Mans with the Luftwaffe conducting the first Oyster minelay on 11 June 1944. They were devastatingly effective, causing confusion and losses of shipping in areas assumed to be swept, until the realisation that pressure mines had been sown and ‘safe speeds’ ordered for all ships that would thus reduce their pressure signature to prevent mine actuation. On 22 June 1944 two oyster mines were recovered near the shore at Luc-sur-Mer, flown back to Thorney Island near Portsmouth and, following their dismantling by scientists, Allied countermeasures were optimised; Hitler had used too few of his new mines, too cautiously, insufficiently densely, laid too slowly, and thus once more had lost the initiative.
* * *
The history of naval minewarfare up to the end of World War II generates many lessons and raises many issues of statecraft and maritime warfare.
The cautious adoption of naval minewarfare in the 17th to 19th centuries by many navies demonstrates the concerns that are posed to military leaders when presented with new technologies. Such concerns are exacerbated when a technology is available for use but for which new risks include no effective countermeasure being available to the side employing it, lest it be reciprocated on the initiator. This was especially the case in the century leading up to World War I, during which moderately effective mechanical minesweeping techniques were eventually developed, but with a further example provided by the case of Oyster (pressure) mines whose deployment in World War II was expressly held up due to their unsweepable nature.
That naval mines can impose significant operational and tactical restrictions on enemy commanders has been highlighted by many of the examples before the end of World War II. The decisions immediately after the Battle of Jutland were for both sides dominated by the presence of mines, reducing routing options for the evading Germans (who used mines to defend their harbours) whilst concurrently guiding the choices of the pursuing British Admiral (who was denied the use of those mined areas). The strategic effects of this chase towards mined waters resonated for the remainder of the war. The inability to penetrate enemy minefields had further strategic and statecraft effects when the Dardanelles campaign failed; this again highlighted the importance of mines as an element of early 20th-century warfare, with the repeated destruction of ships producing a self-sustaining cycle of fear of further loss of life and warships, deterring further attempts at forcing the straits and eventually leading to the withdrawal of British, Australian and New Zealand (among others) forces.
The mammoth undertaking of the North Sea Barrage provides an example of the use of mines to divert shipping along routes otherwise seen as undesirable (due to their increased length) as well as creating a deterrence effect, dissuading some decision makers from ordering their units to even attempt to transit the mined areas. This delayed or disrupted German attempts to foray their U-Boats into the Atlantic Ocean, undermining German strategic objectives.
The two US minewarfare campaigns in the Pacific also provide insights into the strategic use of naval mines. The Japanese used extensive mining of the Pacific Islands to delay and disrupt US military plans to liberate those islands. The US response was a sequential campaign of minesweeping each island in order to allow liberation forces to land ashore and progress their strategic campaign. The US mining of Japan employed a different methodology, imposing a cumulatively disruptive and destructive burden on the Japanese people who were starved towards submission. Such contrasts of desired effect in the same operational theatre highlight the utility of this weapon, especially during periods of war.
[1] Among the minor hiccups, for example, the first attempt at ‘Operation KN4’ off Barfleur (on 26 April 1944) had been abandoned due to the Motor Torpedo Boat minelayers being intercepted and jettisoning their mineload, which was subsequently found to include four mines laid ‘live’ – albeit still set to sterilise on 20 May 1944. (Naval Staff History (1973), p.360).
[2] See NHB: BR 1601 para 44 et seq. for a description of Hitler’s decision processes regarding the deployment of Oyster mines. As late as 24 June 1944 it records: ‘the FUHRER has commanded that, owing to the danger of compromising the new firing circuit, the use of Oyster mines in the Cherbourg Area is forbidden’.
[3] Adolf Hitler was first briefed on the new pressure-mine technology during a meeting at the his Headquarters at 12:30 on 10 September 1943. The D-pressure mines were designated as being ‘for defensive use’ but ‘such minefields are intolerable because [German] movements would be severely curtailed’. See MWC: Fuehrer Conferences on Naval Affairs 1943 dated May 1947, p.97.
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