Umm, you do know of the exploits of the French army during WWI right? They were considered a better military than the British at this point save for the navy of course.
In the second world war it was an absolute absurd decision by Germany to not go through Belgium, but through what was deemed and impossible forested area which cut the French soldiers from each other that lead to their demise. Coupled with Frances refusal to even scout that impassable area because, well, it was deemed unpassable, they were flanked and completely caught by surprise. Even if they had faced the Germans head on, at the very least, it would have been a lengthy battle.
Thus the French were split, many of them saved by the Brits to fight another day. They did fight another day and managed the French Resistance.