Naval History and Heritage Command

Naval History and Heritage Command

Summary of United States Minesweeping Operations in the North Sea Barrage

No. of operation. Date be-gun and date ended. No. of group. Mine-laying data. Num-  ber and depth of lines. Method of sweeping. Average vessls em-ployed. A=Sweep-ers. B=Trawl-ers. C=Chas-ers. Mine-sweeping data.  Percentage of mines in place after 1 year. Remarks.
Date laid, 1918.   Num- ber laid. Ex- ploded  on lay-ing. Num-   ber  mines which  sur- vived. Mines cut. Mines  ex-ploded. Mines coun- ter-mined. Total mines  de-stroyed. Based on     col-  umn     5. Based on     col-  umn    7.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17


First..............
Apr. 29 
to    
May 2
Gen-eral. …………. …………… Per ct.


…………..
…………… No. ft.
 

………….
Experimental oper-
ation to gain
knowledge of be-
havior of mines.
A—12
B—  0
C—  6
91 123 7 221 Per ct.


1 25
Per ct.


1 27

Crossed barrage in central
portion, cutting groups 3,
5A, 7, 11, and 12. Experi-
mented with electrically
charged sweep wire, which
was unsuccessful.


Second.........
May 8
to   
 May 29
12 Oct. 13 3,900 4 3,742 1@  45
1@160
1@240
Transverse prelimi-
nary sweep, fol-
lowed by longitu-
dinal final sweep.
A—14
B—  6
C—  8
747 903 25 1,750 44.8 46.7 Total mines destroyed is in-
creased by 41 mines de-
stroyed on the first opera-
tion and by 34 destroyed
on the final clearance
sweep.



Third.............
June 6
to   
 July 1
9 Sept 19 5,520 6 5,200 2@  45
2@160
2@240
2 divisions sweeping
transversely; 1 di-
vision sweeping
longitudinally
(experimental).
A—16
B—  7
C—  7
1,164 1,049 30 2,329 41.2 44.8 Total mines destroyed is in-
creased by 61 mines swept
by British in May while
clearing their line RQ1, by
25 destroyed by Patapsco
and Patuxent Mar. 20-23,
and by 1 exploded on the
final clearance sweep.


Fourth..........
July 7
to   
 July 8
12A Oct. 13 850 4 816 3@  45
1@160
1@240
Longitudinal sweep-
ing, all ships in for-
mation; group
marked by buoys
in advance.
A—19
B—10
C—  8
214 132 9 355 41.8 43.4 First group marked by buoy-
laying squadron in advance
of sweeping. Longitudi-
nal sweeping used exclu-
sively. Rate of sweeping
approximately tripled.
  July 9
to   
 July 17
11 Oct.   4 5,450 6 5,125 3@  45
1@160
1@240
....do......................... A—19
B—10
C—  8
1,169 783 65 2,100 38.5 41 Total mines destroyed is in-
creased by 60 mines de-
stroyed on first operation
and by 23 mines destroyed
during the final clearance
sweep.


Fifth..........
July 22
to   
 July 24
6 Aug. 19 3,200 12 2,815 3@  45
1@160
1@240
....do......................... A—27
B—  1
C—  8
443 664 59 1,156 36.1 41.1 Because of low voltage ad-
justments on firing devices
it is believed more than 5
per cent of this group ex-
ploded prematurely. As-
suming 9 per cent, the
group yielded 41.7 per cent
net. Total is increased by
60 mines destroyed on first
operation.
  July 24
to   
 Aug. 1
3 July 15 5,395 5 5,131 3@  80
1@160
1@240
....do......................... A—27
B—  1
C—  8
858 1,005 118 2,041 37.9 39.9
  Aug. 2
to
Aug. 3
5 Aug. 9 1,596 19 1,291 3@  45
1@160
1@240
....do......................... A—27
B—  1
C—  8
268 224 14 519 32.5 39.7 Total mines destroyed is in-
creased by 13 mines, which were swept on the first op-
eration.
  Aug. 3 5A Aug. 13 166 6 156 3@  80
1@160
1@240
....do......................... A—27
B—  1
C—  8
21 15 3 56 33.8 35.9 Total mines destroyed is in-
creased by 17 mines, which were swept on the first op-
eration.
  Aug. 4
to
Aug. 6
7 Aug. 31 5,400 7.5 4,793 3@  80
1@160
1@240
....do......................... A—27
B—  1
C—  8
814 828 74 1,746 40 45 Western 9 miles unswept un-
til sixth operation, due to
danger of striking British
mines laid at 6 feet submer-
gence. See group 7 under
sixth operation. Total
mines destroyed increased
by 30 mines swept on first
operation.
Sixth….......... Aug. 13
to
Aug. 16
   

10 Sept. 27 5,400 4 5,216 3@  45
1@160
1@240
....do......................... A—28
B—  1
C—  6
1,096 993 90 2,119 38.9 40.6  
  Aug. 17
to
Aug. 21
   

4 July 30 5,399 14 5,013 3@  80
1@160
1@240
....do......................... A—28
B—  1
C—  6
939 745 74 1,758 32.6 37.9  
  Aug. 21
to
Aug. 24
2 July 1 2,200 4.5 2,120
2@  80
....do......................... A—28
B—  1
C—  6
317 216 22 572 25 26.2 Total mines destroyed in-
creased by 17 swept up by
the British while clearing
their mine fields.
  Aug. 25
to
Aug. 29
1 June 8 3,385 3 3,285 1@  80
1@160
1@240
....do......................... A—28
B—  1
C—  6
523 630 50 1,203 35.5 36.8  
  Aug. 30
to
Sept. 5
13 Oct. 26 3,760 4.5 3,595 2@  45
part
6@  45
....do......................... A—28
B—  1
C—  6
1,189 194 33 1,416 37.7 39.4  
  Sept. 4
to
Sept. 8
8 Sept. 7 4,920 13 4,290
6@  45
....do......................... A—28
B—  1
C—  6
927 212 32 1,171 …………. …………. Made preliminary sweep of
northern three lines only
on account of British line of
mines RQ1, which was still
unswept. See seventh op-
eration.
  Sept. 8
to
Sept.10
7 Aug. 31 5,400 7.5 4,793 3@  45
1@160
1@240
....do......................... A—28
B—  1
C—  6
152 374 37 2,158 40 45 Completed sweeping western
end left on fifth operation.
Total mines destroyed in-
creased by those swept on
fifth operation plus 38
mines destroyed on final
clearance sweep.



Seventh….....
Sept.17
to
Sept.19
8 Aug. 7 4,920 13 4,290
6@  45
....do......................... A—28
B—  1
C—  6
391 88 7 1,761 35.8 41.2 Completed sweeping this
group as soon as British fin-
ished their line RQ1. To-
tal mines destroyed is in-
creased by those swept on
the sixth operation plus 104
destroyed by British while
clearing their line RQ1. To-
tal mines destroyed is in- creased by those swept on the sixth operation plus 104 destroyed by British while clearing their line RQ1.
                1 Estimated.       <24,431>    

Source: United States Navy, Office of Naval Records and Library, Historical Section, "The Northern Barrage" (Taking Up the Mines), (Washington, D. C.: Government Printing Office, 1920), 64-66. 

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