In order to combat the many unwise proposals which were pressed upon me at this time to squander our small stock of mines, I drew up the following paper with which I endeavoured to repel the demands from the Cabinet, the Admiralty and the Fleet. I am aware that these views will be disputed, and I shall no doubt be told that the experience of the later stages of the war has disproved them. I still believe, however, that they were sound and truly applicable to the circumstances of 1914. But I go further and declare that the reasoning held good all through 1915, and 1916. If I am reminded that as part of the life and death struggle against the German submarines in 1917, we were led into a mining policy on a scale so gigantic as dwarfed every previous scheme, and if as the result of this huge diversion of our resources a certain number of German submarines were destroyed, still I assert that these conditions would never have arisen if a proper offensive had been developed by the Royal Navy, as would have been possible at far less cost. All being said, I take my stand as I wrote to Fisher on the dictum ‘Mine in Haste and Sweep at Leisure.’

Mining is mainly of two kinds, ambush mining and blockade mining.

Ambush Mining.

Ambush mining depends on the whereabouts of the field remaining unknown. These mines may be scattered about in patches, or short lines in the neighbourhood of the enemy’s ports or of the approaches to your own ports or landing places on the chance of enemy ships running into them. This chance is not great. The seas are very large; the area mined, even if on a great scale, very small. The chances of preserving secrecy long are not great, and most ambush minefields are soon discovered by merchant ships, or other craft of no military value, being blown up by them. On the other hand, every patch of mines soon hampers the movement of the stronger fleet. The position of the minefields cannot be accurately known. There is very often a tendency for them to drag with their anchors in tide and sea. Also ships cannot always be sure of their positions, and very often when out of sight of land, in weather unsuited to taking observations of the sun, 15, 20, or 30 miles’ error in position may easily arise. The fact that you know generally where your own mines are and when you are getting near their area, but do not exactly know where they are, or exactly where you are, tends to paralyse your own movements, and might easily prevent effective action against or the interception of the enemy’s fleet should it put to sea. The conclusion to be drawn is that ambush mines should be very sparingly used, chiefly in sight of land, and that not very much is to be expected from them. The general failure, so far as our present experience goes, of the German policy of ambush mining with which they opened the war illustrates the truth of these conclusions. The only British warship, apart from the gunboat Speedy (which was actually engaged in fishing up mines), lost by this agency has been the Amphion, and she was drifted out of her course on to the very minefield whose position she knew and which she was endeavouring to avoid.

This is not by any means to decry the use of ambush mines as an immediate part of a concerted tactical combination. It is for this purpose mainly that the British Fleet mine-layers are organised. To lay mines in the course of an enemy before or during a battle, or across his homeward path if he has put to sea, may be operations of the greatest consequence and value, and it would be most unwise to deplete them of their not too extensive store of mines, which should be reserved for this purpose, and not squandered on promiscuous and haphazard uses.

One more class of ambush mines deserves to be noted. A few scattered about on trade routes and off enemy or neutral ports, if well advertised and enforced by a few ships actually blown up, may exercise a very effective deterrent on neutral commerce which may be of use to the enemy.

Blockade Mining.

It is not possible to blockade a modern fleet by mining, even on a very large scale, unless superior force is maintained in the neighbourhood of the minefield to prevent or oppose the mines being removed. In the days when Admiral Togo mined the debouches from Port Arthur the submarine did not exist, and it was possible to maintain a close and constant watch on the minefields, so that even if he was unable to stop the enemy removing the mines he knew when they were doing so, and this perhaps gave some clue to their future intentions. Even so, the Russian Fleet put to sea whenever they wanted to. It would not be possible to keep such a watch now without exposing the vessels so engaged to almost certain destruction from the enemy’s submarines. Further, blockade mining is more effective the closer in it is to the enemy’s ports, and therefore the watching vessels would be continually exposed not only to the attacks of the submarines, but to a greatly superior force of enemy destroyers and light cruisers. In order to maintain them against this, appropriate supports would have to be kept close at hand in proper tactical relation and brought up as the need arose, with the result that more and more ships of greater value would be drawn into the most dangerous area of the enemy’s submarine activities, and considerable operations would develop in waters less suited to us and most favourable to the enemy.

But if the minefield is not watched, the enemy has no difficulty in proceeding to sea at any time he chooses. He will soon learn the existence of the minefield, because one or two small craft will be blown up on it. In the British Fleet the regular mine-sweepers can sweep a clear channel ahead of the Fleet at a rate of 12 knots an hour through any minefield. The Germans have not used, as we have, old gunboats converted as mine-sweepers, but have built a special class of good, fast vessels. It must therefore be assumed that they could sweep a channel at least as quickly as, and probably quicker than, we could. They could therefore proceed to sea at any time if they wished to do so, and with scarcely any delay. Also, if they did not wish immediately to proceed to sea, they could sweep a channel through the minefield of which they would know the existence, and which, being in close contact with land where actual bearings could be obtained, they could follow exactly, and so have continued means of ingress and egress. We, on the other hand, would not know where this channel was, and would be prevented from approaching by the known existence of our own field. The conclusion is that it is not possible by blockade mines to stop a fleet from putting to sea, even if that were what we wanted to do.

Still less is it possible to stop the enemy’s submarines from putting to sea, either by ambush mines or blockade mines. The rise and fall of the tide between high and low water makes a minefield ineffective against shallow-draft craft for half the twenty-four hours. The distance of 50 yards, which is the usual interval between mines, is five times the breadth of a submarine. By diving to 50 feet, the chance of contact with the mine is removed, and only the lesser danger of fouling the moorings remains. It is perfectly easy to sweep a channel for submarines, as for other vessels, at any time. Where there is any uncertainty about the whereabouts of a minefield, trawlers, or small merchant ships with a very few people on board, can go ahead of the submarines and pilot them out. If necessary, vessels could be specially prepared as mine-bumpers, with a kind of cow-catcher apparatus in front of them. We are experimenting with five different methods of fitting ships for mine-bumping, and shall very soon have a number of vessels which can go almost with impunity into a minefield. British submarines have frequently traversed, wittingly and unwittingly, the German minefields around Heligoland, and German submarines are probably traversing our southern mined area with indifference, and impunity, at the present time.

On the other hand, it is a curious truth that your own minefield is a greater deterrent to your own operations than to those of the enemy. You have put it down yourself, so you do not want to sweep it up. You know where it is, though not very accurately. You instinctively try to avoid the waters you have yourself fouled. Nothing has been more valuable than the searching and relentless watching maintained in the Heligoland Bight by our submarines since the beginning of the war. Its vigilance and efficiency have defeated themselves by forcing the Germans to retire actually inside their basins and canal, and thus depriving our submarines of any targets. It would be a great pity to hamper them in their work and expose them to additional dangers for the sake of such vain and illusory precautions. The weak passive defence of mines cannot for a moment be compared as a military measure with the enterprising offensive of submarines.

The above considerations also apply to suggested schemes for shutting submarines in by a network of mines fastened together by wire. Mine-sweepers or mine-bumpers would force a channel through this as easily as through ordinary lines of mines, the only difference being that several being dragged along by the string would be exploded at the same time. Also it is evident that the limitations of this form of defence cannot be carried very far on account of the enormous quantities of material and explosives required. It would be very difficult and dangerous to lay in close proximity to the enemy’s ports and fleets. The process would be slow; the losses certain, and it could in any case block only a very small portion of the 100–mile broad mouth of the Heligoland Bight. Devices of this character may, however, be useful in defending one’s own harbours, and making anchorages submarine-proof, where we can, by our superior strength, prevent our arrangements from being interfered with. A variety of these methods are at present in use, and are being rapidly extended and developed. The following seven principal expedients are being applied:—

(1) Sinking ships with cement or stone in such a way as to form an absolute breakwater and barrier like the mole of a harbour.

(2) Electrical contact mines strung very closely together, and capable of being made dangerous or safe by the current being switched on or off.

(3) Barges or piles, with torpedo nets attached to them.

(4) Loose wire nets of very large mesh, not fastened at either end, which clog round a submarine and entangle it.

(5) Network arrangement, with explosives attached.

(6) Network arrangements, with upright floating spars, which also entangle the submarine.

(7) Long lengths of fishing nets, particularly Portuguese tunny nets, which operate in the same way.

As the war progresses, we shall gradually improvise the torpedo-proof harbours, of which, except on our southern coast, we are now entirely destitute.

I explained to the Cabinet the quantities of mines which we had in store, and which were available in the future. The experience of the last three months seems to justify the partial and limited reliance put by the Admiralty upon mining as a method of warfare.