3. THE SWEEPERS WIN A FOUR YEARS’ BATTLE
On the outbreak of war in 1914, Germany immediately showed that she relied on the mine as a weapon of offence. Within a few hours of the declaration of hostilities a British trawler sighted the Königin Luise, a small converted mail-steamer, laying mines thirty miles off the coast of Suffolk. British destroyers sank her, but the following morning the cruiser Amphion struck one of her mines and went down with the loss of 151 lives.
The regular minesweeping force then consisted of no more than six old torpedo-gunboats. But the Reserve was being mobilized, and by 8th August, 1914, fishing trawlers were at sea, sweeping for mines, manned by their ordinary crews of fishermen. Within a fortnight another hundred trawlers had been requisitioned. So eager was the fishermen’s response that in eleven days the whole force was manned and fitted out at Lowestoft.
By the end of August a clear channel had been swept and buoyed, inshore of the minefield laid by the Königin Luise. This was the beginning of the War Channel which eventually extended from Dover to the Firth of Forth, a distance of 540 miles, and was swept daily. The forces employed on this service were based on the Nore, Harwich, Lowestoft, the Humber, the Tyne and Granton in the Firth of Forth.
The mines with which the sweepers had to contend were globular or pear-shaped, some three feet in diameter, containing about 350 lbs. of guncotton, trinitrotoluene (T.N.T.) or amatol. This explosive, with the firing batteries, occupied about half the space available, the remainder being used as an air chamber to give buoyancy to the mine. On the upper surface were five or more leaden horns five inches long, each holding a glass tube containing a chemical mixture. Contact with a ship fractured the horn and smashed the glass tube; the released liquid then energized the battery, which fired the detonator. On one occasion a whale was killed by hitting the horn of a mine.
When the laying vessel dropped the mine, both the mine and the sinker to which it was attached went straight to the bottom. After a short interval, which allowed the ship to steam clear, the mine was automatically released and rose under its own buoyancy, unreeling its mooring wire, while the sinker remained below. The depth of the mine beneath the surface was regulated by a device called the hydrostat, which gripped the mooring wire when the mine had reached the required height.
The trawler’s task was to cut this mooring-wire so that the mine would either detonate in the wire sweep or rise to the surface, when it could be exploded or sunk by rifle-fire. To facilitate cutting, the Admiralty introduced a serrated wire, the effect of which was to saw through the cable. The sweep-wire was towed between a pair of trawlers about 400 yards apart, and held beneath the surface by a heavy kite, which dived under the water when in motion, just as an air kite rises in the wind. In order to cover as wide a front as possible two or more pairs of trawlers might work together.
Germany began her minelaying campaign with a flying start. She is known to have laid 600 mines off the East Coast alone by the end of August, 1914. Of these, the gallant trawlers had been able to account for only twelve, at a cost of six ships and over half their crews. During the first two months of the war one trawler was sunk for every five mines swept.
It became clear that while the trawlers were invaluable for the routine sweeping of the traffic lanes, their average draught of 14 feet made them too vulnerable for clearing minefields. For this purpose the Admiralty requisitioned a number of excursionist paddle-steamers, which were moderately fast and drew comparatively little water, while the torpedo-gunboats-little coal—burning ships of 800 tons and more than 20 years old—were attached to the Grand Fleet, preceding the capital ships when they put to sea and searching areas where mines were expected.
The first twelve of the regular war-built minesweepers, the Flower class, were ordered on 1st January, 1915, and thereafter their construction proceeded fast. As the war went on, 400 trawlers were built for the Admiralty; others were bought from Norway, Holland and Spain. The minesweeping force expanded so rapidly that it became impossible to man it with fishermen alone. Officers of the Royal Naval Reserve and the Royal Naval Volunteer Reserve joined the Service, while the ratings came from all walks of life and many parts of the Empire. In October, 1917, the operational side was brought under a single head when Captain (now Admiral Sir G. Lionel) Preston was appointed Superintendent, and later Director, of Minesweeping, which position he held until the end of the war, and subsequently when he was in general charge of mine clearance.
As the organisation grew, so did the menace of the mine increase. In June, 1915, the Germans began to use submarines for minelaying. This increased the strain on the minesweeping forces at Harwich, the Nore and Dover, the first areas to be affected. By the end of 1915 the outlook was black. It became even graver as the months went by. In June, 1916, H.M.S. Hampshire, with Lord Kitchener on board, was sunk off the Orkneys by a mine which the U.75 had laid. As larger U-boats came into commission mines were laid farther and farther afield. The trawlers followed them. Their task was made harder still by the delayed-action mechanism which could keep a mine attached to a sinker for any period up to 30 days, so that some channels had to be swept repeatedly before it was certain they were clear.
At last a protection against moored mines was found. This was the paravane, invented by Lieutenant (now Commander Sir Charles) Burney, R.N. It was simple, inexpensive, and sure; a buoyant, torpedo-shaped body of welded steel, 12 feet long, fitted with horizontal rudders to keep it at the required depth. A pair of these devices was towed from the ship’s forefoot, streaming out at an angle of 50 degrees on either bow. The towing wires acted like sweeps when they came in contact with a mine-mooring and protected the whole breadth of the vessel.
Extreme secrecy was preserved about this invention, and although the Germans became perturbed at the increasing immunity of ships in mined areas, they did not discover the reason until after the war. To-day all naval vessels, and all merchantmen whose course lies in waters likely to be mines, carry paravanes, which cannot, however, protect them against ground mines.
The unrestricted U-boat campaign of 1917 was accompanied by a vast increase in submarine minelaying off the British coast. Among the victims was the armed merchant-cruiser Laurentic, which struck a mine off Lough Swilly and sank in 40 minutes with gold to the value of five millions sterling. It was estimated that the Germans laid one mine every hour in British waters. In April alone 515 were swept, a total which far exceeded that for any previous three months of the war; but the cost was heavy: the losses were one sweeper a day for the greater part of that month.
To meet the attack the Admiralty took over every available paddle-steamer and motor fishing-boat, while aircraft and motor-launches were used for locating minefields at low water. By the end of the year over 1,000 miles of coastal water off Great Britain and Ireland were being swept.
On one occasion, off the south-west coast of Ireland, the sweepers merely went through the motions of clearing a dangerous area, left it intact, and steamed back to harbour to await results. It may be that the Senior Officer of the flotilla had in mind Psalm xxxv, verse 8: “Let a sudden destruction come upon him unawares, and his net that he hath laid privily catch himself: that he may fall into his own mischief.” At all events it was not long before the captain of the U.C.44, under the impression that the field had been cleared, began to relay it. His submarine was blown up by one of his own mines and he was rescued by a naval patrol. He is said to have been indignant at the inefficient manner in which the British sweepers had done their work.
Enemy minelaying was not confined to British waters. German submarines laid mines off the coasts of France, Portugal, West Africa. the United States and Nova Scotia, throughout the length and breadth of the Mediterranean, and in the approaches to Murmansk and Archangel. The Turkish mines at Gallipoli, laid for defensive purposes, achieved their object by preventing the British fleet from forcing the Narrows. German surface-raiders, notably the disguised merchant vessel Wolf. laid mines as far afield as the Cape of Good Hope, Ceylon, Australia and New Zealand.
Germany had intensified mine-warfare as part of her policy of destroying British sea-borne trade. But the lessons of history, particularly those of the Napoleonic Wars, when the French pursued the same end, show that commerce-raiding cannot win a war without command of the sea. Germany never secured that command, although during the spring of 1917 she came near to doing so. By the beginning of 1918 the inexorable pressure which the Royal Navy had been exerting for over three years was having its effect, and long before the Armistice British minesweeping had won the mastery over German minelaying.
By November, 1918, the force which had been improvised from old gunboats saved from the scrap heap, fishing craft, and a few excursion steamers, had been expanded into a fleet of over a thousand vessels, stationed at 26 ports at home and 35 abroad, manned by a highly-trained body of men whose life was one of instant readiness, sleepless nights, hard lying, constant vigilance in stormy seas, and the strain of unseen danger.
Besides clearing the path of the merchant-men, the sweepers were always ready to help a ship in distress and their devotion to duty saved many lives. In December, 1917, the hired turbine-steamer St. Seiriol, while sweeping off the Essex coast, sighted the Frances Rose of Liverpool heading straight for a mine 400 yards ahead. It was about two hours before low water, blowing hard, with a heavy sea. Slipping her sweep, the St, Seiriol headed across the Frances Rose’s bows and ordered her to anchor. The extent of the minefield was unknown. Patrol craft and trawlers were sent north and south to stop all traffic, but a few minutes later the Frances Rose struck a mine. The St. Seiriol went alongside the sinking vessel and took off all hands. By that time three mines were showing on the surface. The Commanding Officer gave the order “Stand by to blow up.” But the St. Seiriol remained untouched (although sixteen mines were subsequently swept up in the area) and she proceeded to port at high tide.
The sweepers’ losses were severe: 214 were sunk during the war, an average of one a week. Moreover, when the Armistice came the minesweepers’ work was not ended, for there remained the task of clearing the unswept minefields which had been laid by the Allies and the enemy. That entailed a close search of 40,000 square miles of sea.
The Admiralty appointed an International Mine Clearance Committee, on which 26 countries were represented. The Supreme War Council allotted each Power an area to clear, the largest falling to Great Britain. A special Mine Clearance Service was established in February, 1919, with special rates of pay and conditions of leave. There was no lack of volunteers, and the work was completed by the end of November, by which time 23,000 Allied and 70 German mines had been swept, with the loss of only half-a-dozen sweepers. In the meantime, the Americans had cleared the Northern Barrage between the Orkneys and the Norwegian coast, where 56,033 American and 15,093 British mines had been laid by the end of the war over an area of 6,000 square miles.*
[Footnote] * For a fuller account of the work of the minesweepers in the war of 1914-1918, see Swept Channels, by Capt. Taprell Dorling, D.S.O., R.N.
When the clearance was finished the inevitable cutting down of ships and men began. The trawlers were released to their owners and returned to the fishing grounds; those which had been built for the Admiralty were sold, together with many of the older fleet sweepers, others being broken up or placed into reserve. No fleet minesweeping flotilla was maintained in full commission, and the Minesweeping Division at the Admiralty was disbanded. Later, one flotilla of fleet minesweepers was commissioned for the instruction of junior officers and ratings, and on the re-introduction of training in the Trawler Section of the Royal Naval Reserve, renamed the Royal Naval Patrol Service, three trawlers were attached to this flotilla and fortnightly courses were begun at Portland. But no fast sweepers were built until 1933, when four of the Halcyon class were laid down; these were relieved by more modern vessels in 1939.
During the uneasy years before the war increasing attention was paid to training both officers and ratings and to minesweeping development. Technical investigations were made, sweeping trials were carried out with live mines, and improvements were made to the Oropesa sweep, which had come into use in 1918, being called after the ship in which it was first tried.
In the summer of 1937 the 1st Minesweeping Flotilla was employed on the Non-Intervention Patrol in Spanish waters. In the following year large-scale minesweeping exercises were arranged, and in June, 1939, a handling trial of a magnetic sweep—to be known later as the “Bo’sun’s nightmare”—was carried out. This shows that the Admiralty was not caught completely off its guard by the offensive that was shortly to be hurled against British and neutral shipping, although few realized how serious would be the onslaught when it came.
[Caption] A THOUSAND LITTLE VESSELS like these fought the German mine campaign in 1914-18. The cost was high. One sweeper a week was sunk. But the mine was beaten. Left, paddle-minesweepers at Harwich. Right, armed trawlers in the North Sea.
[Caption] THE SHARK-SHAPED PARAVANE, invented in 1917 and kept secret from the Germans, gave warships and merchantmen their own protection against mines. One to port, one to starboard, they were streamed out at an angle from the bows at the end of cables that cut through mine moorings.
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