Hi ! I would like to know what were the reason why the French didn’t constructed the maginot line at the Belgium border , therefore letting the north undefended by French troops while only half of the French borders was protected . I already know it’s a matter of diplomacy with Belgium but my history teachers wasn’t able to answer why a working agreement with Belgium wasn’t achieved to defend the 2 country . Thanx in advance for the answer ( sorry if there is a problem in my question , first post here and English is not my first language )
This answer by /u/kieslowskifan explains that the French really wanted to build the line along the Belgium\german border and planned to pay for their construction. The plan was that Belgium fortifications and natural terrain would delay the Germans long enough for French forces to join up with Belgium forces and drive invaders out.
The reason that France did not build fortifications along the french \Belgium border was that if Belgium fortified their border with Germany then the French fortifications would be a waste of resources. Also the costs of building and maintaining forts were a major factor along with overestimating the natural defences delaying german forces long enough for the French to reinforce the Belgiums.