Despite the [German–Soviet] pact, Communist resistance started very quickly in the Pas‐de‐Calais. The particular circumstances of the Forbidden Zone allowed for an independence of action that Auguste Lecœur and Julien Hapiot were able to take maximum advantage of. They decided, in August 1940, to begin organising illegal Communist activity against the occupying forces.⁷

[…]

Thus, the Communists of the Pas‐de‐Calais began their anti‐German propaganda very early on. Nevertheless, the Communists of the region did not think of themselves as disloyal to their party and their confidence in the Soviet Union was as strong as ever, it was simply that the daily reality of the Forbidden Zone pushed then more rapidly to a more anti‐German position than their comrades elsewhere.

(Emphasis added. Source.)