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Commander Simon P. Fullinwider, Bureau of Ordnance, to Rear Admiral Ralph Earle, Chief of the Bureau of Ordnance

CONFIDENTIAL                                December 17, 1917.


Subject:  North Sea Barrage.

     1.   The following memorandum is intended to briefly outline the steps in the evolution of the scheme for putting a barrage around the North Sea to contain enemy submarines and prevent their access to the Atlantic.1

     2.   From the time of the entrance of the United States into the war, it became apparent to the Bureau that the most effective way of combatting the submarine was to blockade the enemy’s coast by means of mines or other anti-submarine devices, and the matter shortly resolved itself into the question of placing an anti-submarine barrier around the North Sea, which would prevent enemy submarines from getting into the Atlantic.

     3.   The Bureau made a thorough study of various types of barrage that might be practicable, including nets, nets in combination with mines or bombs, and mines alone. It soon became apparent that no type of net offered a practical solution of the problem, and the Bureau concentrated its efforts on the evolution of an improved type of mine with which such a barrage could be established.

     4.   No type of mine then existing was satisfactory for the purpose because of the great number of mines required for a barrage of 250 miles long and 200 feet deep.

     5.   Early in May 1917, an inventor2 submitted to the Bureau a device which he called “an underseas gun”, which was essentially a buoy or float with a vertical tube pointed vertically downward and with a pendant copper wire which being touched by a submarine would cause the release of the projectile in the above mentioned tube, and the ignition of a propellant in the base of the projectile. The projectile was designed to travel downward along the wire, strike the submarine and penetrate or explode.

     6.   The above device was deemed entirely impracticable and undesirable even if practicable, but there was an electrical principle used in the device which the Bureau believed could be applied to a mine. The inventor, and the Company, back of him, agreed to cooperate with the Bureau in developing a firing device suitable for a mine and the result was a mine with an antenna of any desired length, which length was finally fixed at about 100 feet. Contact by a submarine with any part of the antenna explodes the mine.

     7.   On July 18, 1917, the Bureau announced to the Chief of Naval Operations,3 the above mentioned development of a mine peculiarly adaptable for use against submarines.

     8.   Under date of July 30, 1917, in a letter to the Chief of Naval Operations,4 the Bureau proposed a joint British-American offensive operation, comprising the establishment of submarine barriers from the coast of Scotland to the coast of Norway, across the English Channel, across the Adriatic, and finally at the Dardanelles. With this plan was furnished an estimate that 125,000 mines would be required at a total cost of about $40,000,000. and the necessary appropriations were obtained from Congress.

     9.   On August 15, 1917, the Bureau furnished Admiral Mayo5 a copy of the above mentioned letter, and also a memorandum on the same subject, containing additional details regarding the proposed barrage. These papers served as a basis for discussion between Admiral Mayo and the British Admiralty, and finally on October 16, 1917, at a conference in the office of the Chief of Naval Operations, Admiral Mayo, Chief of the Bureau of Ordnance, and others, a decision was reached to proceed with the manufacture of 100,000 mines for this project. At this conference Admiral Mayo produced a British study of the barrage project, which was based on the information previously furnished by the Bureau of Ordnance, in which the barrage was divided into three portions; one on the western end mined with British mines of the horn type and the other two portions to be mined with American mines. This is the basis of the present arrangement between the British and American Naval Establishments.

     10.  It is now expected that the first shipment of American mines to England will take place on February first, and that the total number of mines required will be furnished within four months from that date, which will permit the barrage, at least the American portion thereof, to be planted during the good weather of 1918.

(Sig) S.P. Fullinwider

Source Note: TDS, DSI-AC, Fullinwider Papers. The notation “(N3)/MC” appears in the top-left corner.

Footnote 1: For a discussion of the Navy Department’s decision to proceed with the North Sea Mine Barrage, see: Ernest K. Lindley, Franklin D. Roosevelt: A Career in Progressive Democracy (New York: Blue Ribbon Books, 1932), 154-157; and Dennis C. Conrad, “Attacking the U-Boat: The North Sea Mine Barrage”, accessed 28 December 2018.

Footnote 2: The inventor was Ralph C. Browne. Lindley, Roosevelt: 156.

Footnote 3: Adm. William S. Benson.

Footnote 4: This letter has not been found.

Footnote 5: Adm. Henry T. Mayo, Commander-in-Chief, United States Atlantic Fleet.

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