Documentary Histories
WWI
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.
