3. When practicable to augment the present antisubmarine effort at Dover by

(a) A mine barrage (deep and surface) from Kentish Knock to Dunkerque.

(b) A deep mine barrage from Hastings to Touquet Point. (c) A system of ground listening devices operated from shore, located about 20 miles eastward of Dover Straits.

4. To organize immediately a continuous surface patrol east of line Start Point-Sept Isles, with a total force of 30 destroyers or P-boats, the patrol to be assisted by ground listening devices operated from shore, by air patrols, and by kite balloons.

5. To augment the above patrol by a series of deep mine fields; planting continuously in the usual areas of enemy operation until he abandons the Channel.

6. Until extensive deep mine fields can be laid, to employ a few hunting groups in the eastern Channel in conjunction with the patrols, and to develop tactics for "mining in" a bottomed submarine with deep mines.

7. To concentrate hunting effort west of the line Start PointSept Isles; and to assist this effort by deep mine fields and patrols in waters favorable to bottoming, off both Cornwall coasts.

8. To place orders immediately for 70,000 additional mines. 9. To increase the efficiency of the Channel convoy system by the following measures:

(a) Carrying a kite balloon on one ship of each escort.
(b) Placing convoys in a formation of wide front which de-
creases as the depth increases.

(e) Adopting a policy of determined depth-charge attack
by several escorts against every attacking submarine.
(d) Arranging convoy sailings so as to avoid passage at
night during moonlight.

MISSION.

(a) To decrease immediately shipping losses in the English Channel.

(b) To deny English Channel to enemy submarines, while still permitting commercial traffic.

ENEMY FORCES STRENGTH, DISPOSITION, AND PROBABLE INTENTIONS.

Enemy submarines operate from the northern bases in general as follows:

Normally about 10 big submarines per month use the Channel for passage, going past Dover as a rule on the surface at H. W. slack, and during darkness. Lately this number has decreased, probably

due to the increased efficiency of the Dover barrage. They usually keep in the deep gut so as to facilitate diving.

There are generally 3 or 4 small U. B. or U. C. submarines from the Flanders Flotilla operating in the Channel; principally against overseas through-channel traffic, which normally brings them nearer to the English than the French coast. In bad weather they usually bottom in Lyme Bay, the Plymouth Bight, or other bights where sea is smooth. At night they probably cruise slowly at from 1 to 3 knots. Strategic value of the Channel to the enemy.-The great focal area of shipping, lying in general between the south coast of Ireland and the French northwest ports, must continue to be the center of the enemy submarine effort, if his submarine campaign is to succeed. The distance to this area via the Channel is 480 miles from Zeebrugge and 660 miles from Helgoland. North-about via Fair Island these distances become 1,320 and 1,300 miles, respectively.

If passage through the Channel is denied, there will result a reduction of about 40 per cent in the number of small submarines that can be maintained in the focal area, and about 20 per cent in the case of the larger type.

Besides its value as a passage to and from the focal area, the Channel is also of immense value as an operating theater. Of all traffic to and from the United Kingdom, more than half passes through the Channel, exclusive of the vast crosswise traffic on military service. The Channel is itself a concentrated focal area, offering to the enemy the further advantage of narrow width, great length, and sheltered waters.

Moreover, cross-channel traffic is a vital link in the communications of the British Army in France.

The enemy's probable intentions.—

1. The desire to reduce passage time and thus increase the number of boats operating, as well as to take advantage of good hunting en route, will persuade the enemy to proceed to station via the Channel unless it is too dangerous.

2. An enemy submarine operating in the Channel has two main problems to consider (mine-laying submarines not included).

(a) The problem of getting in touch with shipping.

(b) The problem of charging batteries.

As a rule, shipping keeps to the north side of the Channel, so that must be the operating area for submarines.

The submarine, to get into touch with merchant shipping during daylight, will keep a periscope watch when vessels are near, and will operate on the surface at other times. The submarine has always in mind the possibility of attack and plans to avoid attack by(a) Submerging and running.

The increasing ability of the antisubmarine craft to pursue submarines when submerged will increase the tendency of submarines to "bottom;" so that submarines will always prefer positions where water is less than 40 fathoms deep and the bottom is not rocky.

As listening devices become fitted to seagoing vessels, the danger to submarines operating off soundings will increase, possibly sufficiently to counterbalance the tendency to operate offshore during good weather; in other words, the operations of hunting groups may drive submarines to operate in narrow waters the year round. If this should be the case, it would be doubly important to make those waters highly dangerous for submarines.

3. The submarine fears

(1) Destroyer attack.

(2) P-boat attack.

(3) Depth charge attack-any vessel.
(4) Aircraft attack.

(5) Deep mine fields.

In general, the avenue of escape from (1), (2), (3), and (4), above, might lead into danger of (5), particularly if the submarine were pursued. If, however, the submarine knew that there was real danger of (5), then its correct course should be to bottom immediately until danger has passed or until dark.

4. Undoubtedly submarines charge their batteries during daylight whenever possible to do so unobserved. At night they prefer to charge where there is small chance of interruption.

5. The geographical position of Cornwall, combined with shelter afforded on one coast or the other in almost all weathers, will make that immediate locality a desirable hunting ground for the enemy in rough weather.

OUR OWN FORCES.

The enumeration of our forces is omitted. They comprise numerous units for all varieties of antisubmarine effort, and are being increased constantly.

They are divided into six separate major commands, having no coordinating heads-three British and three French. Coordination between British and French forces is accomplished through their respective Governments. These conditions render it impossible to cope adequately with an enemy whose forces, by means of a flexible system of command, are enabled to conform quickly to changed conditions. For example, a group of submarines known to be operating just south of the Isle of Wight would be met only by our forces based on Portsmouth, while at the same time we might have large British and French forces in other near-by areas, some unemployed, in readiness, others operating in regions vacant of submarines.

While it is true that the various Channel commands are supposed to, and do, cooperate, the extent to which such coordination prevails necessarily depends upon the personalities of the respective district. commanders and upon the cordiality of the relations existing between them. Furthermore, any commander will be reluctant to detach forces specifically assigned to him for the protection of a given area for duty elsewhere, unless the responsibility for such a move is taken by a senior.

Obviously the organization of our Channel forces prevents their employment in accordance with the best principles of warfare. Without unity of command our forces can not be operated with the necessary flexibility, nor be employed as a whole to the best advantage.

Our present Channel command is about to be further complicated by the addition of American vessels, thus introducing a third nationality in forces already suffering the handicap of two languages. It would be desirable to man with American crews the French antisubmarine forces (exclusive of those assigned to harbor defense) now operating in the Channel. Incidentally, this transfer would permit France to commission certain cruisers needed for ocean escort work, but laid up owing to lack of sufficient personnel.

The importance of denying passage through the Channel is heightened by the present plans for the Northern Barrage, which, if successfully completed while Dover remains unblocked, will prove a wasted effort and serve the enemy better than ourselves by forcing him to use the route most advantageous to him.

Owing to its narrowness, the Dover Strait appears the most logical point at which to block passage to enemy submarines. If this be successfully done, it also will fortify other effort having in view the denial of the Channel as an operating ground.

Efforts to block Dover have been vigorously prosecuted for two years and are greatly hampered by strong currents, smooth bottom, heavy seas, great rise and fall of tide, and comparatively great depths of water. While present prospects for successful blocking at a comparatively early date appear good, the great importance of denying passage through the Channel to enemy submarines renders it imperative that we augment the present effort at Dover by other means, if practicable.

In considering mine barrages to the eastward of Dover, we prefer to go far enough east to insure weak currents; but we are limited by the necessity of having the line near enough to receive proper surface support against raids. The line Harwich-Dunkerque is as advanced as we can well protect. Here currents reach 2.3 to 4 knots occasionally, the rise and fall of the tide is between 10 and 20 feet, the hold

ing ground is good, and depths of water moderate. It will suffice to mine only between Kentish Knock and Dunkerque, through a distance of about 40 miles, with an average depth of 20 fathoms; 12,000 American or destructor mines would give theoretical immunity against surface or submerged passage. This barrage would afford some protection against raids to the Dover patrol forces.

West of Dover the first position which offers any considerable advantage over the practical difficulties encountered in the Straits is the line Hastings-Touquet Point, 37 miles long, and requiring 10,000 American or destructor mines for theoretical immunity against passage. The great amount of shipping passing this vicinity requires that a mine barrage here should be deep. This barrage would be practically immune against surface raids.

The line Isle of Wight-Cape Barfleur has the distinct advantage of permitting a barrage to be laid to the surface if shipping can all be diverted through the Solent. It has the great disadvantage of strong currents, which, at springs, reach 5.4 knots near the French coast and 3 knots throughout the rest of the line. Consequently, this position should not be chosen if it can be avoided.

The last position which we need consider is the line Start PointSept Isles, 90 miles long, and requiring 40,000 American or destructor mines for the theoretical immunity against the passage of submarines. It is across currents not exceeding 2 knots, except close to the French coast. The southern half of this line is little frequented by incoming traffic, and therefore surface mines would not present much danger to shipping; the northern half, however, could be a deep mine field only.

The necessity for making this line, as well as all others, at least in large part a deep field, requiring a great patrol force, leads to the conclusion that the Dover area, where lines are shorter, is the best locality in which to deny passage.

In the Dover area the efficiency of the patrol may be increased and its protection facilitated by the installation of a system of ground listening devices operated from shore. To avoid noise interferences due to ordinary traffic (as well as to the movement of loose material on the bottom) such a system would have to be placed about 20 miles to the eastward of the Straits.

We now come to the consideration of the other phase of the Channel question-that of denying the Channel as a theater of operations.

Unless both entrances can be practically closed, there will always exist some probability that submarines will enter from one end or the other to prey upon the large volume of concentrated traffic. We have examined the possibility of closing the western mouth and concluded it to be impracticable, so that, regardless of the efficiency