why SHAPE moved from France to Belgium in 1967?
In the spring of 1966, when French President Charles de Gaulle decided to take France out of NATO's integrated military command structure, he declared that all non-French military headquarters and installations must depart French territory by 1 April 1967. This meant that NATO military headquarters such as SHAPE and AFCENT (Allied Forces Central Europe, located in Fontainebleau) plus major U.S. headquarters like the U.S. European Command located just outside of Paris, had to leave French territory within a year.
NATO began looking for a suitable site for SHAPE and believed that for psychological reasons it was important that the headquarters remain on the continent of Europe rather than move across the English Channel to the United Kingdom. Germany was not considered a good location for SHAPE because it was too far forward in terms of the potential threat at that time, so the Benelux countries were approached about the possibility of hosting the NATO military headquarters that needed to leave France.
The Netherlands offered to become the host nation for AFCENT and Belgium offered to host SHAPE. The Belgian government then identified a site just north of the city of Mons in western Belgium that was already owned by the government and thus could be quickly turned into the site for SHAPE. The site offered to NATO by Belgium was Camp Casteau, a 200-hectare summer training site for the Belgian Army.
Belgium also offered to host NATO's political headquarters, because the NATO Allies had decided to move this headquarters from France at the same time as the military headquarters, even though France had not demanded the removal of NATO's political headquarters.