Captain Joel R. Poinsett Pringle, Chief of Staff, Destroyer Flotillas, to United States Destroyer Flotillas Operating in European Waters
UNITED STATES NAVAL FORCES
OPERATING IN EUROPEAN WATERS,
U.S.S. MELVILLE, FLAGSHIP.
22 January 1918.
From: Force Commander.
To: U. S. Destroyer Flotillas Operating in European Waters.
Subject: Submarine attacks.
The following figures from British Admiralty reports, chiefly concerning attacks on convoys, are quoted for information.
December showed a marked increase of submarine attacks on convoys, 20 having been made against 9 in November. Losses numbered 13 vessels against 4 in November (when there were more convoyed sailings), distributed as follows (for December):
In 10 attacks on 34 homeward convoys, composed of 412 vessels, 6 ships were sunk and 3 damaged.
In 10 attacks on 33 outward convoys, composed of 513 vessels, 7 ships were sunk and 2 damaged.
The per cent of losses to sailings of convoyed vessels increased from .8% in November to 1.1% in December.
The number of British ships convoyed remained the same for December, 88%, as for November. Likewise the number of Foreign ships convoyed was the same, 82% of sailings.
In December there was a tendency for losses to concentrate in home waters. Of the total attacks upon United Kingdom trade, 78%, and 90% of British losses, occurred in that area. In the British Channel and its approaches, 25 ships were lost in December, compared with 21 in November.
Day and night attacks on British vessels for December were fairly evenly distributed. Of 57 night attacks, 37 were made when the moon was up, and 20 under no moon. Of ships attacked by night, a larger per cent were sunk or damaged than of ships attacked by day; the figures being 60% for 48 day attacks, and 77.7% for 45 night attacks. Submarines maintained their tendency to operate inshore by daylight; but at night during the month they attacked with increased frequency beyond 10 miles from shore.
The Convoy System has caused losses to drop chiefly in the Scilly, Fastnet, and Tory triangles.
The diminishing losses—until the December increase—have not been due to lack of targets, as the enemy declare. For April, May, and August, average British sailings were 1,264 per month. For September, October, and November, 1,230 per month.
During the four months ending with December, 3003 British vessels were convoyed on the Atlantic, Gibraltar, and Dakar routes. Of these, .7% were sunk in convoy. Of 302 independent sailings for the same period, 7% were sunk. The same figures for the same months, of total United Kingdom oversea sailings, are: .75% lost in convoy; 5.7% lost independently.
During the five months ending with December, of 59 vessels sunk while in convoy, 39 were sunk in home waters, and of these 22 in the English Channel. For the same period, 13 vessels were sunk before joining their escort, 17 within 3 days of dispersal, and 10 by falling out of convoy.
For the whole period of unrestricted submarine war—11 months—there has been a great reduction in the number of attacks made by day as compared with those by night. The latter have remained about constant. Torpedo attacks have continued remarkably constant. Decrease is chiefly in gunfire attack, owing to increased defensive armament of merchant ships. In April, 56% of ships under the British flag were armed, as against 90% on January 1, 1918.
J. R. POINSETT PRINGLE.
Chief of Staff