Tannenberg, Preussen och Hansestadt Danzig

The auxiliary minelayers Tannenberg, Preussen and Hansestadt Danzig, together with a convoy of eight minesweepers, approached the mined area from the north at 15 knots after laying a mine barrage in the Gulf of Finland. The weather was still, with brilliant afternoon sun.

The minesweeper Sandön was stationed in the area to guard the minefield. Sandön had limited speed options as she only had one boiler fired up in order to save on precious fuel. As the German convoy approached the minefield, Sandön, despite struggling to maintain high speed, used both signal flags and audio signals to attract attention.

Sandön eventually made contact with the nearest convoy ship and further warnings were issued. The warnings were ignored, and at 18.10 Tannenberg, Prussia and Hansestadt Danzig entered the first line of mines. Although the engines were off, the speed caused the three ships to slip into the second mine line and be hit again. At 18.30 Tannenberg and Prussia sank, soon followed by Hansestadt Danzig.

Sandön, together with the convoy ships which were shallow-draught and could avoid the mines, were able to salvage some survivors. Sandön took 16 badly wounded German sailors. Some of these men later died at the hospital in Kalmar. The convoy ships then set course again for Germany.

On 20 August of the same year, the minefield was swept in order to investigate the possibility of salvaging the ships. However, it was determined that a salvage operation would not be profitable. Instead, the ships were blown up in 1952 and major sections were scrapped. Today, only some of the ships’ remains rest on the bottom of the sea.