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German submarine activities on the Atlantic coast of the United States and Canada online

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to keep lookout for enemy submarines and warn and divert the convoy before the
enemy submarine can sight it. (Omit; see change.)

13. Considering a suggestion that interference with shipping would be made more
difficult by sending convoys out of more ports than are so used at present, it was
concluded that available escort vessels were too few, that land transportation would
be disarranged, and that harbor facilities would be taxed too much beyond their
normal capacity, to offer any success for such a measure. Accordingly,

(m) The dispatch of convoys should be limited to New York and Hampton Roads,
as at present.

14. The foregoing applies mainly to the area between Nantucket Shoals and Cape
Hatteras. Shipping out of the Gulf, including the important fuel-oil supply, has
not as yet been convoyed and escort force is not available to establish such a convoy

15. A division of submarines and an aviation station are located at Key West, and
dependence must be placed upon these and upon local and passing traffic and the
coastwise lookout service for information of hostile submarines in the vicinity; and
in such event, shipping out of the Gulf of Mexico should be routed south of Cuba.
(See change.)

16. In the event of submarines operating against shipping coming from the canal
shipping may be routed via Cape Horn; but action as to this would be too much
subject to the particulars of the situation at the time for any more definite conclusion
by this Board. (Omit; see change.)


17. In order to route incoming shipping clear of submarine dangers, it is the
consensus of the Board that the best means would be return convoys. This would
insure the correct receipt of and compliance with routing instructions. Not enough
cruisers being available to convoy return shipping, however, there is no choice but
that —

(ri) Return shipping to the United States must be independent of convoys. (See

18. Considering the great extent of coastal waters inside the 50-fathom curve, it
will be at best possible only to keep one avenue of approach to New York and one to
Hampton Roads sufficiently swept for a practical degree of safety from enemy mines.
Our sweeping task is lessened by the fact that only a small number of mines can be
brought over by submarines. Judging by the latest experience abroad, these may be
planted in small groups in several widely separated locations. There being only a
few mine sweepers available, they can be employed to the best advantage by search-
ing out a route clear of mines rather than by attempting to keep several fixed routes
swept clear. In searching formation sweepers can cover more ground than in sweep-
ing formation. The Board concludes, therefore —

(o) That incoming shipping should be routed into port through approach channels
that have been found by searching or sweeping to be safe.

181062°— 20 10



19. To the end that vessels may be wamecl daily of the positions of submarines
and mines anti receive directions for their movements —

(p) Return shipping to the United States should be controlled by radio from the
United States.

20. To provide for the necessary secrecy of such radio control —

(q) Each belligerent vessel should carrj' a commissioned communication officer of
her own or of United States nationality. Such officer would be in charge of codes,
would decipher code messages and transmit them to the master of the vessel, but
would have no authority over nor responsibility for the vessel. He need have no
seagoing experience, but must be trustworthy and of sufficient education: hence to
supply these communication officers, our trained personnel need not be drawn upon.

21. The foregoing pro\d8ion must be undertaken immediately, to be available for
use when wanted; but wholly apart from its value in emergency, the Board strongly
recommends ite adoption as a measure that will greatly promote the safe routing of
ships in the war zone and thereby reduce tonnage losses.

22. Until commissioned communication officers shall have been established on
board belligerent vessels, as provided in paragraph (q) above, other means to facili-
tate communication with incoming ships are recommended to be established, con-
sisting of a system of secret routing for ships approaching this coast similar to the
method in use in the war zone. The Board does not consider this as an alternative
but only as a temporary means, pending the adoption of the commissioned officer
system, which alone of the two has the requisite reliability and flexibility.

Military Offensive.

23. The foregoing measures cover the procedure necessary to carry out the policy
recommended affecting shipping, namely, to continue sending it out with the least
possible interruption. These measures alone constitute one means of combating
enemy submarines both actively, by resisting their attacks upon convoys, and
passively, by wearing out their endurance, ultimately depriving them of their main
object — breaking the supply abroad. But active measures to remove the submarines
from our waters are necessary, in addition, lest their stay be prolonged to our dis-
advantage and the attendant risk to shipping continue long enough to have serious
internal effect in this countrj^

FIXED and local DEFENSE.

24. Connected with measures of active offense the subject of purely passive de-
fensive measures were considered. Fixed fortifications under the Coast Artillery
should be sufficient to prevent the actual penetration of our interior waters. In
addition to this, all districts have patrols at the entrance to principal harbors, and
in the second, third, and fifth districts there are guns afloat in the old battleships
Massachusetts, Indiana, and Iowa. These means the Board considers sufficient to
frustrate any attempt which might be made to enter interior waters.

25. Request has been made of the War Department to supplement the forces of the
naval districts employed in coast defense by one or two gun batteries at salient points
along the coast which might be bombarded. While such an attack might cause no
great material damage, popular clamor might compel some military dispositions
seriously affecting the active theater of operations. The War Department has replied,
however, that no guns can be employed for this purpose.


26. Submarine nets were considered as part of fixed defenses. As to offshore nets
outside New York and Hampton Roads and Long Island Sound, even if the material


were available, the operation of planting them is too extensive to be undertaken
within a short time; and even when in place, the nets are of small effect unless thor-
oughly patrolled, not to mention the effort and rnaterial reciuired for upkeep.

(r) The Board concludes, therefore, that no outside net.s should be considered, but
that inside nets as maintained or planned by the Coast Artillery, and at Base Two
and Cape Henry by the Navy, should be retained, and that these nets, together with
fixed fortifications and harbor patrols, will afford sufficient security against any hostile
attempt to enter a principal harbor.


27. Mines which are submerged at a depth which is dangerous to surface craft,
including submarines (subsurface mine fields), would be a greater embarra88ment to
our own Aessels in the situation under consideration than to the enemy's. We can
not afford to endanger or restrict the movements of our own vessels, which are at best
very limited in number, and there being no hostile surface vessels involved, the
Board concludes —

(s) That no subsurface mine fields should be included in the present plans. (See

28. At present the Mark VI mine has no attachment for safety in case of shallow
planting, and the mines of earlier marks are not capable of deep planting without
modification of the depth-regulating apparatus. Even with such modification, they
could not be planted at a rapid rate. These mines also have no safety provisions
against shallow planting. As a whole, therefore, we have no mines suitable for deep
mine fields at present. A safety attachment for the Mark VI mine is being developed,
and mines of that mark are being manufactured in considerable number, so that
within several months we may have a supply which could be used in emergency for
deep mine fields on our own coast, though destined for another project abroad.

29. The free operation of our own submarines would, however, be endangered in
the vicinity of deep mine fields, and hostile submarines may be expected to operate
far enough offshore to be clear of any deep fields large enough to embarrass them,
unless we used a number of mines beyond any possibility of supply. The chance of
deep mine fields contributing materially to the destruction of enemy submarines is
remote on account also of the small number of submarines that may be expected
to operate. The Board therefore concludes that —

(t) Unless hostile acti\'ities on our coast be prolonged beyond control by other
measiures, no deep mine fields should be planted; but

(m) That naval districts be prepared to plant mines and that steps be taken to make
mines available for planting a deep barrier across the approaches to New York Harbor
and Hampton Roads. And, further (see change),

(v) That districts should be prepared to announce fictitious mine fields in the event
of the emergency contemplated actually arising and to route shipping accordingly.

30. As a whole, the passive defenses of the first, second, tliird, and fifth districts are
deemed sufficient for the defense of the principal harbors in those districts.


31. The purpose of measm-es of actr\e offense is to locate and destroy the submarines.

32. The principal operations of these submarines must be conducted in the offing
of New York, off the Capes of the Chesapeake, and in the Florida Straits and Yucatan
Channel. In order to continue their operations beyond their self-contained capacity,
the enemy submarines must replenish from some near-by base or by some means of
supply from our coast or some neutral source.


33. To locate the submarines we have an organized lookout service in operation
along the coasts in the several naval districts and also a secret service of sufficiently


wide extent and connections. These should be warned to be on the lookout for evi-
dences of any use of our coasts and of any support to enemy submarines from on or
near our coast.

34. The same applies to the possibility of the enemy's use of a base in the Bahamas.
Connection of our intelligence service with that of the British in the Bahama Islands
should be sufficient provision to secure timely information. In this connection it is
stated by the commander of squadron 2, cruiser force, that a reconnoissance of the
Bahama Islands shows little suitability of that region for use as a submarine base.


35. The Naval Air Service, in addition to assisting the escort of convoys, may con-
tribute materially to the locating of submarines by air scouting off our coast, including
the use of kites and dirigibles, especially between Nantucket Shoals and C'ape Hat-
teras. It is assumed that this may and will be done should the contemplated emer-
gency arise.


36. The situation has not yet sufficiently developed to enable the Board to do
more than outline the offensive action that may be taken. The conclusion was
reached —

(aa) That provision should now be made for forces to be available where likely to
be needed, to detect and locate enemy submarines, to act upon information of their
whereabouts, and to be capable of attacking a submarine if encountered.

37. The kind of force that should accompany convoys has already been stated. In
addition, it is the Board's conclusion —

(66) That, in addition to harbor and inshore vessels, there should be a force of de-
stroyers and of submarines ready to act upon information of hostile submarines near
our coast.

(cc) That the strength of these should be, in the first naval district, 2 destroyers, 1
submarine; third naval district, 4 destroyers, 5 submarines; fifth naval district, 4 de-
stroyers, 5 submarines.

38. The possibility of there being more submarines capable of service at the New
London and other bases, and of more destroyers being under shakedown, after the
building program shall have begun to yield more frequent deliveries, was taken into
account, as also the submarines at Key West and Panama and the vessels already in
the several districts. The forces named in paragraph (cc) above are the minimum
increase needed.


39. The lookout service and reports of coastwise and other passing traffic first come
under the cognizance of the naval districts, and these districts will have at disposal
the forces intended to act according to the situation that may arise. The success of
measures against submarines in the majority of cases will probably depend on the
celerity with which forces act on information received. This indicates that their
direction and control should be in the hands of the respective naval district com-
mandants, and the Board so recommends.


40. Adverting to the policy laid down in paragraph 7, the Board, examining the
sources that could be drawn upon for the force specified in paragraph (cc), concluded
that the best practical plan was to utilize new destroyers and new submarines during
the shakedown period before departure for European waters.

41. Considering first the destroyers, this would involve a delay at first, but this is
unavoidable if adequate provision is to be made for the contingency imder con-


sideration. Besides, the delay is not so long as at first apparent. Not less than two
weeks is the probable minimum required by the average new destroyer for pre-
liminary shakedown. To this some few days more may be needed for new fittings
constantly being added, which would be installed on board on this side instead of
abroad. During the time so spent the destroyer would be availalile for emergency
if here; but if abroad she would not be operating so no operating time is lost on this
account. Fiu-ther, by a somewhat longer shakedown time on our coast, together
wdth a quick run across instead of a slow passage for shakedown en route, the ultimate
date of beginning service in the war zone would be little affected. The same applies
to the submarines.

42. The Board concluded, therefore —

(dd) That new destroyers should remain on our coast for one month shakedown after
commissioning, to be available for service in the event of the appearance here of
hostile submarines; but that not more than nine at one time need be so detained if
prepared earlier to sail for distant service.

{ee) That the nine destroyers so detained shall be stationed one in the first, and four
each in the third and fifth naval districts, the commandants of which shall be in-
structed to use them as necessary in the event of hostile submarines appearing on this
coast; otherwise not to employ them, but instead to allow them all possible freedom
in their training for active service.

(Jf) That to provide the necessary submarines for the emergency service con-
templated, new submarines should have a shakedown period of two months; their
training course not to be interrupted but to continue in its normal course from its usual
base; but upon the appearance of hostile submarines, one division to be escorted to
New York and one division to Hampton Roads; fiu-ther, while based on these places,
to continue their training to such extent as the situation may permit; the respective
naval district commandants to observe the same attitude as toward destroyers, stated
in paragraph {ee).

43. Still other forces are required, which, with available sources, may be stated

{gg) Participation by any force from the Atlantic Fleet, other than the Cruiser
Force as now employed in convoy duty, is not counted upon.

(hh) A force of 30 submarine chasers each, based on New York and on Hampton
Roads, will be needed for convoy escort and listening service. To provide these,
the earliest deliveries intended for other districts should be diverted to the third and
fifth districts until the necessary total numbers are present in these districts.

(m) One destroyer and one submarine permanently employed in experimentation
are counted upon, with one new destroyer under paragraphs {dd) and {ee), to make up
the force for the first naval district.

{jj) In order to accomplish the sweeping task without delaying shipping, in or
outbound, there must be based at New York and Hampton Roads, sweepers enough
to keep in service two sweeping groups of three pairs each. For this there must be
18 or more mine sweepers at each place named. As neither the third district nor the
fifth has this number, the Board recommends that sweepers from the first and second
districts be added to those of the third district when the occasion arises, and, similarly,
those from the fourth district to go to the fifth district.

(kk) For the air service to be performed, it is estimated that a force of 40 airplanes
will be needed at Rockaway Inlet and at Hampton Roads in order to insure 16 planes
being ser\dceable for escort duty; and this number should be made available. (See


44. The armament of such vessels of the naval districts as are seaworthy is too light
for engaging a single submarine Avith success, except by surprise. It is therefore
recommended —


(II) That in view of the possible appearance of submarines armed with 5 or 6 inch
guns, the armament of district vessels be replaced by larger calibers as soon as prac-
ticable, but not to the deprivation of suitable armament for vessels navigating the
war zone.


45. In order to increase the navigating difficulties of submarines, especially in fog
and darkness, and also to prevent the converging of shipping at a point favorable for
submarines to operate, the Board recommends —

(mm) That immediate steps be taken to install on board all outside lightships on
the Atlantic Coast radio and listening equipment;

(nn) And that, upon the appearance of a hostile submarine in American waters, all
submarine signal bells be stopped, the bells and whistles on outside buoys silenced,
, and Nantucket Shoal lightship be withdrawn. (See change.) (See additions (oo)
and (pp).)

46. The Board has included in this report only such detail as has seemed necessary
to make its recommendations clear, to show the extent to which existing dispositions
have been taken into account, to make a decision where there has been or may be
doubt or wide difference of opinion, and especially to strengthen the statement as to
the minimum of increase in force necessary to retain on this side. In \dew of exist-
ing machinery for executing plans, it seems inadvisable to go further into details.

(Signed) M. Johnston,

Rear Admiral, U. S. Navy.
Philip Andrews,

Captain, U. S. Navy.
S. S. Robinson,

Captain, U. S. Navy.^
L. R. De Steiguer,

Captain U. S. Navy. ~
R. R. Belknap,

Captain, U. S. Navy.
L. McNamee,

Captain, U. S. Navy.
, J. R. Y. Blakely,

Captain, U. S. Navy.


Commander, U. S. Navy.
J. V. Babcock,

Commander, U. S. Navy.
E. J. FoY,
Lieut. Commander, U. S. Navy.
Approved as changed by modifications, etc., appended.

W. S. Benson.

Navy Department,
Office of Naval Operations,

Washington, March 6, 1918.
The foregoing plan, "Defense Against Submarine Attack in Home Waters," with
the following alterations, modifications, or changes, is approved. Steps will be taken
immediately to put it into effect.

modifications and changes or alterations — OUTBOUND SHIPPING.

Par. 12 (c). That the best practice is to have the coastwise shipping proceed by
day, hugging the shore and keeping within the 5-fathom curve, or as near it as prac-
ticable. Also, since it is the policy of the shipping committees charged with such


"work to allocate the smallest and least valuable ships to the coasting trade, it, as a
matter of expediency, should be the policy to protect said shipping by the means
within the capacity of the naval districts through which the coastwise shipping passes
rather than to attempt to divert guns from ships in the trans-Atlantic trade or to allo-
cate cruisers for the protection of our coastwise trade, except in such cases where the
districts could not afford protection or the guns were readily available. That if it
were found expedient to route coastwise ships at night that they should sail inde-
pendently, being routed with due regard to the warnings received of the location
of enemy submarines.

Par. 12 (/). Change to read: That convoys should be preceded to the 50-fathom
curve or as far beyond as necessary by four submarine chasers equipped with listening

Par. 12 (g). Change to read: That air scouts should patrol the convoys' intended
course out at least to the 50-fathom curve and as far beyond as circumstances permit,
or until darkness comes on.

Par. 12 (h). Omit the words "and by one or more escorting submarines for lookout."
It is the policy to use our submarines offensively against hostile submarines, and their
movements are influenced by the movements of hostile submarines, not by the move-
ments of our convoys.

Par. 12 (j). Add at the end of paragraph: "and also of destroyers if advisable."

Par. 12 (l). Omit entirely.

Par. 15. Last two lines, change to read: "shipping out of the Gulf of Mexico should
be routed north or south of Cuba as circumstances existing at the time renders most

Par. 16. Held to be not sound, as the delay thus caused to shipping practically
reduces its efficiency to a lower limit than the actual submarine sinkings could impose.

Par. 17 (n). Add the words "until such time as convoys can be established."

Par. 27 (s). That in view of the slight advantages to be derived as compared to
the inordinate risk to shipping, the subsurface mine will not be used offensively
against hostile submarines. That it is legitimate to use it defensively, but that such
use should be confined to the purpose of barring entrance and exit to our principal
shipping ports and confined to the lowest limits compatible with a fair degree of
safety. That even when a defensive mine field is laid, a clear and ample passage
must be left for the transit of shipping, and this passage must under no circumstances
be mined, but be patrolled and protected by other means. That all mines upon
being detached from their moorings must become innocuous. That the three places
to be considered now as coming within the scope of defensive mining are New York,
capes of the Chesapeake, east entrance to Long Island Sound.

Par. 29 (u). After the words Hampton Roads, add: "But that owing to the great
demand for mines abroad this step be not considered now."

Par. 43 (kh). Read that a force consisting of at least one squadron of 20 airplanes
will be needed at each station (Rockaway Inlet and Hampton Roads), and that this
number should be made available as soon as practicable, not to interfere with the
European program.

Par. 45 (nn). Omit the words "and Nantucket Shoal Lightship be withdrawn."

Par. 45. Add new paragraph : (oo). "Be prepared upon special order of the Navy
Department to withdraw all light vessels on the Atlantic coast, but this will be done
only when the necessity is strongly apparent."

Par. 45. Add new paragraph: (pp). "Establish listening stations at the entrances
to Chesapeake Bay, New York, and the east end of Long Island Sound. If these
stations prove effective and are needed, to extend the system to other important

(Signed) W. S. Benson.



Navy Department,
Washington, March 13, 1918.

[Memorandum for all divisions of OflRce of Naval Operations.)

Subject: Execution of a plan for defense against submarines in home waters.

1. In accordance with the attached plan and approved modifications, the following
parts thereof are assigned to the divisions of this office for information and action.
Where a part has been assigned to more than one division, the officers in charge will
cooperate in its execution in accordance with the duties of their respective divisions.

2. Provisions of the plan that require the action of any bureau will be prepared by
the head of the division concerned and transmitted to the bureau after signature by

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