On June 12, 1936, the German and French armies engaged in a rather brutal siege at Charleroi.
To keep the German Army at bay beyond the borders, the French government really went all out. They coordinated with the 100,000 troops supported by the British, the 100,000 mobilized by the Belgians within their own country, and their own 400,000 troops, intending to hold the line from Charleroi to Kortrijk.
The good news was, the British-French-Belgian force, numbering 600,000, successfully halted the German Army north of Kortrijk to Charleroi.
But the bad news was, all the Belgian urban cities to the north, including the original capital, Brussels, and another major city, Antwerp, had all fallen into the hands of the Germans.
At present, the territory controlled by the Belgian government was less than one-fifth of its original size, and the 100,000 troops they managed to sustain were about the limit for Belgium.