The domain was used as a defensive position in May-June 1940 during ‘Operation Dynamo’ to protect the embarkation of allied troops heading for Great Britain. Just like elsewhere in the Westhoek, numerous carriages, weapons, ammunition and food were left behind at the Cabour domain in a hurry.
From 1940 onwards, a field battery was set up in the Cabour dunes, which would be designated 'Stp. Ost-W-049' ('Stützpunkt Oostende West') or ‘Schlieffen’ (from 12 December 1942). The core of this battery, which formed part of the Atlantic Wall, was constructed along the south side of the domain, at the height of the farm ‘De Woestijn’ (Cabourweg). The field battery was built in two phases. In a first phase (June 1940-March 1942), six open gun batteries were built in brick, intended for 155-millimetre guns. In a subsequent phase (between 1942 and 1944), the actual field battery was built, with the construction of a command bunker (type R610) and four gun bunkers (type R611). In addition, a shooting range, a grenade range and various roads were constructed on the estate. Remaining infrastructure from the First World War, among other things, was also used. The officers stayed in the castle, the artillerymen slept in the barracks of the former field hospital from the First World War. Prisoners of war were housed in barracks, which were surrounded by barbed wire. The infantry, responsible for the security of the area, was billeted in the De Woestijn farm.
The Schlieffen field battery was abandoned by the Germans on 6 September 1944. During the siege of Dunkirk (6 September 1944-8 May 1945), Czech units took up positions on the Cabour estate. These positions were repeatedly attacked from Dunkirk.
The water extraction system on the eastern part of the domain was used excessively intensively by the German occupier, which led to salinization that often approached and sometimes reached the maximum permissible limit.