Ever since 1930, the Munich and Stuttgart intercept stations had, during the summer months at the time of the occupation of the Rhineland, reconnoitered the Demilitarized Zone for suitable intercept sites for use against France. After sites had been selected, the construction work was completed with the help of trustworthy civilians. Several weeks before the Remilitarization of the Rhineland, an intensive monitoring of France was ordered. As the result of the intelligence, German troops marched in without fear of reprisal.