4. FIGHTING THE SECRET WEAPONS
Every available minesweeper of the Royal Navy and the Royal Naval Patrol Service was at her war station by the end of August, 1939. During the summer, the Admiralty had bought 67 trawlers and had ordered twenty new ones from the shipyards. Others were taken over as they returned from the fishing grounds. As one naval officer said, “They threw the fish out and threw us in.”
In every war since the days of Elizabeth, Britain has suffered from an initial shortage of small ships. But whereas the emergencies of 1914 had demanded improvisation, in 1939 those lessons had been learnt and plans had been made from the experience garnered. There was, moreover, an invaluable nucleus of officers and ratings who returned to the Service with practical knowledge of mine-sweeping in war, and also a number of patriotic and enthusiastic R.N.V.S.R. amateur yachtsmen who had learnt the elements of minesweeping during their holidays with the 1st Minesweeping Flotilla at Portland.
The Minesweeping Division at the Admiralty once again became responsible for all vessels and material. The Director and his staff collected and disseminated intelligence regarding enemy minelaying, gave advice on tactical counter-action, and laid down the searched channels through which shipping might pass. In the Operations Room a permanent watch plotted the movements of the sweepers and recorded the position of every mine that the enemy was known to have laid, and of every ship known to have been mined.
At each Naval Base a Port Minesweeping Officer took command of the trawlers which swept the new War Channel. On a mine being reported or swept, the position was buoyed, the local traffic diverted, and, if necessary, the port closed. If mines were found in the War Channel, the convoys were kept back until the dangerous area had been cleared. A priority message was sent to the Minesweeping Division, where its information was checked and then broadcast to all shore stations and ships at sea. Patrol vessels were posted near the dangerous area to warn merchantmen which might not have received the message. Whenever possible, the masters of sunk or damaged ships were interviewed as soon as they came ashore.
The first ship to be mined in the present war was the British steamer Magdepur, which blew up and sank off the East Coast on 10th September, 1939. Six days later the City of Paris struck a mine but escaped with little damage. As the weeks passed losses became more serious, and statements made by a prisoner of war revealed that the enemy was discharging magnetic mines from submarines. This evidence appeared to be confirmed by a number of unexplained explosions and sinkings off the coast.
Hitler had boasted of his “secret weapon” and it seemed that this might be the magnetic mine. It was not, however, a new invention, for the Royal Navy had used magnetic mines off the Belgian coast in the previous war, and, so far from its being a secret, an American citizen, Mr. Caesar Marshall, had been granted a British patent for such a device in 1918. Other inventors had experimented with mines of similar type, and the Mine Experimental Department of H.M.S. Vernon was well aware of their existence; indeed, its own magnetic mines were in an advanced state of development.
The magnetic mine is so called, not because it is attracted to a ship’s hull, but because it is detonated by a magnetic needle which becomes active when a large mass of iron passes in its field. When the mine is laid on the sea bottom it can operate only in comparatively shallow water, but within its range it can cause far more damage than the moored mine, since the moored mines blows a hole in a ship, usually for’ard, which may be localized, whereas the explosion from a ground mine strikes the vessel under her bottom amidships, opening up the plating of the hull, shattering the machinery and the pipes, and frequently breaking her back.
Against this weapon neither the existing sweeps nor the paravane availed. But counter-measures were taken, first with the “Bo’sun’s nightmare,” which was still in the experimental stage. This was a wire sweep to which a number of magnetized bars were attached and towed between two ships just off the sea bottom. Large electro-magnets and barges with coils of wire were also used; even aircraft were employed. The first magnetic mine was detonated in the Bristol Channel, but although the sweepers were rapidly fitted with new devices and the officers given instruction in their use, none was wholly satisfactory and the sinkings continued at an alarming rate.
A doctor cannot prescribe a remedy until he has had the opportunity of diagnosing the disease, and the officers of the Mine Experimental Department of H.M.S. Vernon could not find the effective antidote to the magnetic mine until they had studied a specimen and discovered its mechanism. Every effort was made to recover a magnetic mine intact, but for some time without success.
Then it appeared that the enemy was dropping the mines from aircraft. This was all the more serious, because it rendered our own mine barrages, which were a protection against surface-layers and submarines, of no avail. Between 18th and 22nd November, fifteen merchant ships were mined, including the Japanese liner Terukuni Maru and the Dutch steamer Simon Bolivar. H.M.S. Belfast was damaged and the destroyer Gipsy sunk.
The danger to shipping had suddenly become intensified, and it seemed that merchant traffic would be paralysed unless the remedy could be found. The men in the sweepers did all they could, but they were powerless against this weapon new to their experience. They looked to the scientists to give them the means to combat the offensive, but that the scientists could not do until they had discovered exactly what they had to fight.
The first definite evidence that the enemy mines were being laid from air came on the night of 21st November, when aircraft, believed to be Heinkel 115s, operating from bases on the islands of Sylt and Borkum, were seen to drop mines in the Humber and in the estuaries of the Stour and the Thames. Observers reported that the mines looked like sailors’ kit-bags suspended from parachutes. Officers from H.M.S. Vernon were sent to East Coast ports to investigate. They could discover no further information. None came in next day. The situation had become very grave. Shipping in three rivers was held up. The Minesweeping Division at the Admiralty and all officers ashore and afloat were working under a severe strain. But as yet there was no conclusive proof of the nature of the mine.
Shortly after midnight on the morning of the 23rd, Lieutenant-Commander J.G.D. Ouvry, R.N., of H.M.S. Vernon, was called to the Admiralty from the London hotel where he had been awaiting such a summons. He packed his bag immediately and reported to the Director of Minesweeping. He was told that at ten o’clock that night sentries at Shoeburyness, on the Thames Estuary, had seen a German aircraft drop an object into the sea near the beach. At first they believed the dark shape to be a parachutist. They waded out into the water to investigate, but the incoming tide forced them back. A report had been made to the naval authorities, who realized that the chance of recovering a magnetic mine intact had come at last. Lieutenant-Commander Ouvry was told that the mine should be uncovered at low water, which would be at 4 a.m. A car was waiting to take him and Lieutenant-Commander R.C. Lewis, R.N., also of H.M.S. Vernon, to Shoeburyness. Their orders were to examine the mine and recover it at all costs.
Two hours later they were met at Shoeburyness by a naval Staff Officer, a party of soldiers equipped with lights, ropes and stakes, and two photographers. It was a dark night, and rain was falling. In the river a large company of ships lay at anchor, unable to sail until the channel had been cleared of the unknown. A frozen-meat ship had caused a mine to fire as she swung to the turn of the tide.
Led by one of the soldiers, the party set off in the darkness, splashing through the pools left by the ebbing tide. At length the light of the torches revealed a black object lying partially embedded in the sand. The two officers advanced to the attack, while the soldiers in the rear illuminated the mine with an Aldis signalling-lamp.
They found the mine to be cylindrical in shape, about 7 feet long, made of some aluminium alloy, with tubular spokes on the nose and a hollow tail containing a massive bronze spring for projecting the parachute. There were two sinister fittings near the fore end. One was evidently a hydrostatic valve. The other was impossible to identify. It was made of polished aluminium and secured by a screwed ring sealed with black wax. As this fitting seemed more likely to harbour a primer and detonator, Lieutenant-Commander Ouvry decided to tackle it first.
Lieutenant-Commander Lewis took an impression of the securing ring on a sheet from a signal pad in order that a brass (non-magnetic) spanner might be made to unscrew it. Flashlight photographs of the mine were taken from all angles, and measurements made for purposes of description. It was decided to wait until noon, when the mine would be again uncovered, and the soldiers tenderly lashed it down with the ropes and the stakes. On their way back to the car the party came upon the parachute spread out on the sand. It was made of white silk and took eight men to drag it above high-water mark.
At 6 a.m. the Vernon officers had just finished breakfast when they received a message that another mine had been sighted about 300 yards from the first. They immediately set off again and waded out in the deepening water to find it. The occupant of a moored hulk nearby told them that it had been submerged for some minutes, and they decided to wait for the falling tide.
A preliminary report was then framed and sent by car to the Admiralty, together with copies of the photographs which had been developed and printed. At one o’clock both mines were uncovered. By that time the special mine-recovery party had arrived from H.M.S. Vernon, with Chief Petty Officer C.E. Baldwin in charge, bringing a set of non-magnetic tools as an addition to those which had been made at Shoeburyness during the night. A tractor lorry with a crane fitting was kept in readiness in a sheltered position on the foreshore. While daylight photographs were being taken of the first mine, the officers examined the second; it was found to be on a different slew from the first, with its nose inclined downwards, and was more battered.
It was then arranged that Lieutenant-Commander Lewis and Able Seaman A.L. Vearncombe should remain on the foreshore while Lieutenant-Commander Ouvry and Chief Petty Officer Baldwin tackled the first mine. Lieutenant-Commander Ouvry outlined a definite sequence of events, which the others would be able to observe clearly from the distance—“in case of a mistake on my part,” as he put it..
He and the Chief Petty Officer then set out across the sand, having first emptied all metal objects from their pockets. It has been said that they volunteered for the task of rendering the mine safe. There was no question of this. It was the work for which they had been trained, the work which they had been waiting to do for weeks. Whatever their feelings may have been, they accepted the risk, serious though it undoubtedly was. They had no means of knowing whether the mine had some special trap that would cause it to detonate should an attempt be made to dissemble it. They were like men who advance along a jungle path which may well be ambushed. But both were experts at their work: and they had their courage.
They started on the aluminium fitting on the upper part of the mine. The keep-ring unscrewed easily and there was no difficulty in raising the fitting. This Lieutenant-Commander Ouvry did, however, with the greatest caution, since he believed was handling either a detonator or some sort of magnetic needle. It proved to be a detonator.
Confident that this operation had removed the principal danger, he summoned Lieutenant-Commander Lewis and A.B. Vearncombe to help him turn the mine so that he could reach the fittings hidden by the sand. This they accomplished without mishap, and a second detonator was discovered, of a type similar to that of the German horned mine. The fangs had now been drawn.
“We felt on top of the world!” wrote Lieutenant-Commander Ouvry afterwards.
By 4 p.m. they were satisfied that they had made the mine innocuous. It was hoisted on to the lorry, for despatch with the parachute to the Vernon the following morning, and an hour later a report was made to the Admiralty that the mine had been recovered intact. Lieutenant-Commander Lewis returned to London that night, and at 11 p.m. attended a Board of Admiralty conference at which the First Lord, Mr. Winston Churchill, heard the full details.
The mine reached the Vernon next day. Its total weight was 1,128 lbs. and it carried an explosive charge of 660 lbs. in the fore end. The conical stern became detached when the aircraft dropped the mine, thereby releasing the parachute. When stripped down by the experts of the Vernon its mechanism proved to be what one of them called “a scientist’s paradise.” Mr. Churchill had given orders that work was to proceed day and night until the answer had been produced. In twelve hours the solution was passed to the Admiralty: it was indeed a magnetic mine, and all its secrets had been laid bare.
Lieutenant-Commanders Ouvry and Lewis were awarded the D.S.O., C.P.O. Baldwin and A.B. Vearncombe the D.S.M. Lieutenant J.E.M. Glenny, R.N., who rendered the second mine safe, received the D.S.C.
The recovery of these mines was not only among the most gallant deeds of the war, but was a turning-point in the long and bitter conflict between minesweeper and minelayer. Hitler had relied on the magnetic mine to destroy the British mercantile marine. It is on record that Captain Hans Langsdorf, of the Graf Spee, assured his prisoner Captain Patrick Dove, master of S.S. Africa Shell, that Germany regarded it as the secret weapon which would be the decisive factor in winning the war. He declared that it had been invented eight years previously and that since then the cleverest German technicians had failed to find an antidote.
“Now the British navy has to start where we began eight years ago,” he said.
But what one man’s brain can contrive, another’s can resolve. There is a parry to every thrust, an antidote to every poison, once the analysis has been made, and as soon as the secrets of the magnetic mine had been discovered it was possible to provide the counter-measures.
A new sweep was evolved, the principle being to create a magnetic field which would activate the needle of the mine, and the sweepers soon began to achieve satisfactory results. Moreover, since the paravane could give ships no protection against ground mines, they were provided with a simple but effective device known as a “degaussing girdle,” which could be fitted to vessels of any size: a band of wire fastened round the hull, level with the upper deck and energized by an electric current, which has the effect of neutralising the ship’s magnetism and giving her almost complete immunity. At one time 1,200 miles of cable were being used weekly to fit the ships.
It was this degaussing gear which made it possible to send R.M.S. Queen Elizabeth on her maiden voyage to New York, and it has saved countless other vessels, great and small, from destruction. It seems ironical that the unit of magnetic flux, which is one of the means of countering the magnetic mine, should derive its name from a German scientist, Carl Frederick Gauss (1777-1855). One Senior Officer of a minesweeping flotilla found it a name to conjure with when, after an abortive search for a magnetic minefield, he complained that he had been sent on a wild gauss chase.
Once these remedies had been found, the losses were far less dangerous. The sweepers, however, were faced with a resourceful and remorseless enemy, who knew how to vary his tricks and was deterred by no considerations of chivalry in his designs for paralysing British commerce. Time after time he launched an intensive mining campaign, and at one period attacked defenceless fishing craft to prevent their being used as minesweepers. Occasionally a mine or float would be picked up inscribed with threatening messages. One, scrawled in white paint, read, in somewhat ungrammatical German rhyme:
“Geb ich ein gut Geleite
Churchill hat dan große Pleite.”
which may be translated:
“Guide me on my way aright
Then Churchill will be in sad plight.”
It now reposes in H.M.S. Vernon’s museum, alongside the most treasured “carcass” of all, the first magnetic mine.
The German occupation of Norway, Denmark, Holland, Belgium and France, and Italy’s entry into the war, placed an even heavier burden on the sweepers. A new phase of mine-warfare began: the laying of contact mines by E-boats after a preliminary aircraft attack on the sweepers. In these offensives the sweepers gave a good account of themselves, although there were inevitable casualties, including one trawler sunk with nineteen of her crew. But many aircraft were brought down. H.M.T. Berberis, who destroyed one and severely damaged another off the East Coast, received a signal of congratulation on her efficient gunnery from the Board of Admiralty, which also bestowed praise upon the whole Patrol Service in the Nore command for its excellent spirit in the face of repeated air attacks. Nor was the campaign confined to the waters off the East Coast, for Dover, the Solent, the Bristol Channel, the Mersey and the Clyde were visited by minelaying aircraft. The Dover trawlers, besides being bombed and machine-gunned from the air, were under frequent shell-fire from the French coast.
The Admiralty’s answer to this campaign was sweeping by night. This was unknown in the last war and it presented a complex problem, particularly in the tidal channels of the Thames Estuary. But it was mastered under the pioneer leadership of Captain G.B. Hartford, D.S.O., R.N., and during the winter of 1940 the sweepers of one base covered 1,000 miles every week. The strain on officers and ratings was severe, and the work was not done without loss, but the casualties were far less than they would have been in daylight operations, exposed to air attack.
The result of the sweeping during the first twelve months of the war was an achievement of which the little ships could be proud, but for them there was no resting on their sweeps. From day to day there was no knowing what fresh “secret weapon” would confront them. None knew better than they that across the water the best brains in Germany were devising new engines of destruction, one of which at any moment they might have to meet.
In due course it came. Observers began to notice that minelaying aircraft would cut off their engines before releasing their mines. There were reports of more unexplained explosions, some of them in water which had been swept for ground and contact mines. The new type was found to be actuated by the underwater sound emitted by the passage of ships through the water. Once again the experts of H.M.S. Vernon tackled the problem and took measures—which of necessity must remain secret—to counter the new campaign.
So the battle of brains goes on. It was certainly well for British shipping that the German claim to have sunk H.M.S. Vernon (in fact a shore-based establishment) was a Goebbels lie. While the Germans continue to produce their “ingenious variations,” as Mr. Churchill has called them, the men of the Vernon continue to lay their counter-plans, deducing from their experience what the next trap may be, so that they may be ready when it comes and, if possible, at least one jump ahead in their precarious work of finding the right equipment to place in the hands of those whose duty it is to sweep the sea.
[Caption] NECKLACE OF MINES lying around the deck of a German minelayer in the North Sea. It is September, 1939; the attack has begun. The crew stands ready.
[Caption] THE “BOSUN’S NIGHTMARE”, so called because of its tangles, was the first answer to the magnetic mine. The cylindrical bar is the sinker. Oval-shaped floats are called “blobs.” The wire sweep is magnetized.
[Caption] DEATH BY FLASHLIGHT. In the black ebbing waters of the Thames estuary before dawn on 23rd November, 1939, lay this German magnetic mine, keft, the first to be recovered intact. The men of H.M.S. Vernon (a naval shore establishment, not a ship) were told to secure it “at all costs.” Right, lashed down in the morning light, the “secret weapon” is about to yield its secrets. The spokes on the nose are to prevent it rolling or washing away once laid.
[Caption] A PARRY TO EVERY THRUST. Arrows point to the famous H.M.S. Vernon invention, the “degaussing girdle,” around the liner Queen Elizabeth. This electrically energized belt neutralizes the ship’s magnetism and gives her almost complete safety from magnetic mines.
[Caption] DEAD LETTER. The German message on the captured mine says: “Guide me on my way aright, then Churchill will be in sad plight.”
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