It is a curious fact that all the preliminary work was done by Germans, not to mention the German engineers employed by the contracted firms who carried out the construction of the fortified locations. Undoubtedly the information they passed later to the Abwehr proved very valuable. German workers employed by SA des Enteprises Réunies who belonged to the Pieux Frankignol Company³ were involved in building A,B,B’,C and D bunkers (especially B). This fact was known to the officers controlling Belgium’s national defence and they imposed restrictions with the leading company that Belgians must oversee the work. Furthermore the gendarmerie had to check all workers within a radius of 500 metres from the bunkers and casemates and prohibit entry to foreigners (particularly Germans).

The finished bunkers/casemates A,B,B’,C and D (all at Vroenhoven and Veldwezelt) were occupied between 18 and 20 February 1935. They were staffed by cyclists of the border protection unit stationed at Lanaken (Cyclistes Frontières), and with the exception of bunker C had the following personnel: one officer or NCO as bunker commander: two sergeants responsible for the upper and lower floors respectively, one senior private as a light machine-gunner and two men to supply him with ammunition, one senior private and four men for observation, liaison and to man the searchlight.