German shaft of a World War I countermine. The construction of this shaft must be part of the underground activities in the run-up to the Mine Battle of June 7, 1917.
The Germans, who have occupied the Wijtschate-Mesen ridge since the autumn of 1914 and can therefore enjoy a great strategic advantage, are building a strong defense in depth. The Allies are forced to work underground if they want to break through this German front.
As early as the autumn of 1915, British Tunneling Companies started excavating deep mine shafts and tunnels in the direction of the German positions between Hill 60 and the Ploegsteert Forest, a zone 15 kilometers wide. A total of 24 deep mines were provided under the German positions (19 of which would eventually explode on June 7, 1917). The ideas for a large-scale mine battle were integrated by the army staff into the plans to straighten the front arc between the Ypres Salient and the French border, so that a breakthrough could be forced in a next phase (which would then become the Third Battle of Ypres).
The German army becomes aware of Allied underground activities. The German Mineure tried to locate and sabotage Allied activities using counter-mine shafts, tunnels and 'camouflet charges'.
From the beginning of 1917, Mineure excavated counter-mine shafts. Two counter-mine shafts are dug in the Wijtschatebos, which are named Daniel and Dietrich. Through these countermines the Germans target the Allied construction of the two deep mines at Petit Bois.
What is striking about the preserved construction is the use of specially cast concrete blocks, which are curved in shape. Normally, such shafts are made of wood, possibly reinforced with steel rings. In Mesen, one shaft of a German countermine is also said to have been built with such curved concrete stones, but it has now completely disappeared.
Dietrich is built in a concrete bunker, with two access stairs. The shaft probably provides access to a wooden tunnel at a depth of 45 meters, which, however, will not be completed. The roof of the concrete bunker was demolished after the First World War, reportedly to recover the rebar.
(Immovable Heritage Inventory)