German Submarine Warfare 1914-1918 in the Eyes - British Naval ...

Total sinkings in the North Sea and Atlantic rose from 716,000 BRT in 1915
to 1,789,000 BRT in 1918. In 1915 an average of two boats daily deployed in the
North Sea and Atlantic. In 1917 and 1918 there were twenty-nine boats out daily.
The sinkings per boat fell from 864 BRT in 1915 to 201 BRT in 1918. In short,
more boats resulted in less sinkings.
The whole submarine merchant war in more detailed numbers:
Table 8: U-boat merchant war 1915-1918 40
North Sea + Atlantic Mediterranean
U-boats
BRT sunk U-boats
BRT sunk
out per
torpe- per Uboat out per
torpe- per Uboat
day mer-
doed w/o and day day mer- doed w/o and day
chant war total warning out chant war total warning out
1915 2 715 997 36 % 864 1 344 732 26 % 1,041
1916 5 951 613 19 % 500 4 886 372 39 % 648
1917 29 4 343 055 67 % 416 10 1 135 288 77 % 323
1918 29 1 789 919 85 % 201 9 703 166 96 % 247
7 800 584 3 069 558
Statistics for submarines in the Mediterranean are treated separately from the
Atlantic because in both theatres Germany pursued different objectives: in the
Mediterranean they fought a general war against the world merchant fleet without
any specific focus in time or place. Most ships sunk there were Italian or French,
bound for Mediterranean ports. This affected England only indirectly. In the
Atlantic, however, it was tried in three phases of unrestricted submarine warfare
with the object of strangling Britain by sinking all ships bound to or from there,
British, Allied or Neutral.
We see a general increase in the percentage of sinkings without warning. In
1917 two-thirds of the tonnage was sunk without warning, in 1918 nearly all
shipping was sunk without warning. The method has significance. Unrestricted
warfare applies if the vessel was attacked without warning. Restricted warfare
means that the target was stopped by verbal order, signal, by warning shots or a
combination of all three; neutrals were identified; ships’ papers were examined and
the cargo was inspected for contraband. Thus, cruiser rules for the taking of prizes
were in force and destruction of the merchant vessel was done after all personnel
were safely evacuated and their passenger and crew supplied with the means and
direction for making a safe landing ashore. Only armed merchant ships were
allowed to be sunk warningless.
The sinking rate decreased generally in both theatres. In fact, during the
second half of the war sinkings declined from about 500 BRT per day to
approximately 200 BRT. Analysts in Room 40 commented on the drop: “The average
destruction per boat at that time (second half of 1916) worked out at 17,000 tons per trip.
40 Numbers based on: NA, HW 7/3; on: NA/ADM 137/3921; on: NA, ADM 137/4817; on: NA,
ADM 137/4814; on: NA, ADM 1/8509/1; on: Spindler, Handelskrieg; on: Bendler, UB- und UC-
Boote.
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