Neutral Belgium — let the Allies in?

Since 1936, Belgium had pursued a "policy of independence", keeping its distance from the great powers and refusing any formal military commitment with France and the United Kingdom. But in the winter of 1939–1940, the German threat became more definite, and the Mechelen incident confirmed that an offensive would pass through Belgian territory.

The dilemma became pressing. Authorising the Franco-British armies to enter Belgium pre-emptively would allow a defence in depth to be organised before the attack, but would break neutrality and perhaps furnish Hitler with the pretext he was seeking. To refuse this was to rely on a defence improvised at the last moment, with the Allies able to rush in only once the invasion had begun.

Léopold III and his government had to choose. Let the Allies in ahead of time to prepare a joint defence. Hold a strict line, calling on the Allies only after an actual aggression. Or negotiate secret cooperation plans without public commitment. The whole balance of Belgian security — and the fate of the coming battle — turned on this judgement.