Siegfried von Forstner Ships attacked Ships attacked

| Date_ | Ship | Nationality | Tonnage | Fate |
|---|---|---|---|---|
| 7 February 1942 | Kalliopi | Greece | 4695 | Sunk |
| 7 February 1942 | Robert E. Hopkins | Great Britain | 6625 | Sunk |
| 7 February 1942 | Toward | Great Britain | 1571 | Sunk |
| 8 February 1942 | Newton Ash | Great Britain | 1571 | Sunk |
| 11 May 1943 | Antigone | Great Britain | 4545 | Sunk |
| 11 May 1943 | Grado | Norway | 3082 | Sunk |