Numbers and Percentages of Losses of Ships Sunk in Each Quarter of the Unrestricted U-boat Campaign 1917-18 in the North Sea, off the East, South and West Costs of the UK, in the Western Approaches, and in the Atlantic (including the Bay and US Coasts), other Areas and Unknown


Grove, Eric J. The Defeat of the Enemy Attack on Shipping 1939-1945, Table 2.
Navy Records Society, volume 137 (Ashgate Publications), 1997.
Despite the title, this book contains some valuable information on the WW1 submarine campaign, and is well worth consulting.

(Ships of 500 GRT and above)
Feb-Apr '17 May-Jul '17 Aug-Oct '17 Nov '17-Jan '18 Feb-Apr '18 May-Jul '18 Aug-Oct '18
North Sea & East Coast 62 (12%) 47 (10%) 48 (14%) 32 (11%) 22 (8%) 42 (21%) 15 (9%)
UK South & West Coastal Waters 127 (24%) 86 (18%) 89 (27%) 128 (45%) 141 (51%) 48 (23%) 64 (40%)
Western Approaches (including West Coast) 135 (26%) 137 (30%) 43 (12%) 6 (2%) 13 (6%) 18 (9%) 8 (5%)
Atlantic and Bay (and US Coast) 67 (22%) 90 (19%) 66 (19%) 31 (11%) 26 (9%) 33 (16%) 41 (26%)
Other Areas and Unknown (NOT including Med.) 37 (7%) 23 (5%) 24 (7%) 2 (1%) 4 (1%) 11 (5%) 15 (9%)
Notes French coal trade convoys started early FEB (night sailings). End of April Scandinavian & E. Coast Convoys started MID-JULY home N. Atlantic convoys start. Convoy assembly ports: Funcrana, Lamlash, Queenstown, Milford, Devoport, Falmouth AUG Outward ocean convoys. Gibraltar home convoys start AUG. Home S. Atlantic convoys start SEPT. MID-OCT Gibraltar convoys made "through". Through med. convoys start OCT. Through med. convoys start NOV. Queenstown given up as convoy assembly port JAN. Very slow N. and S. Atlantic ships included in Gibraltar convoys in MAR. Ocean-going ships in Irish Sea start using Liverpool late MAY. Dover barrage effective from AUG. Large u-boats North about Scotland from FEB. FCT (French Coal Trade) daylight sailings start MID-JUNE. Special south coast Inshore Route started JUNE. More ocean going ships in convoy in Irish Sea in JUNE. Southend used as convoy assembly port (till OCT) from JUNE. Milford-Rosslare convoy started in JUNE. Offensive off US East Coast started JUNE. North Cornish coast convoys started END OCT.

Notes (taken directly from the book):

The "Other Areas and Unknown" are included in order to show an important effect of the ocean convoy system, that is the marked decrease in 'unknown' losses, following upon its introduction. In fact, they virtually disappear.

It will be noticed that the percentage of Atlantic losses is highest in the last quarter - 41 ships, 26%, of the world's losses.

It will also be noticed that a drop in losses occurs in the UK South and West Coastal Waters in the May-July '18 quarter (48 ships, 23%) upon the effective blocking of the Strait of Dover and a consequent U-boat offensive in the North Sea and off the East Coast. Losses in S. and W. coastal waters, Aug-Oct 1918, rise again - 64 ships, 40% losses when comprehensive East Coast Convoy system instituted.

Air escort and support (day only) was provided to all ocean convoys when within aircraft range and weather conditions permitted.

Convoys with air escort were virtually immune from attack. In June 1918 aircraft provided air escort and support to coastal convoys also, in lieu of area patrol. No successful attacks were made on coastal convoys so escorted.

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Last Updated: 8 March, 1998.