The French are quite flexible, a fact that the Germans can testify to; however, the French are also very tough, with the Germans again as witnesses.
Do not look solely at World War II; you must start from the era of Louis XIV to understand an interesting phenomenon about France.
In terms of cunning and deceit, France is not on par with the UK.
In terms of militarism, France definitely does not compare to Russia.
Yet, opportunism, deceit, and combativeness—all these qualities are present in France. They are not outstanding, but sufficient.
The colonial territories might not be as vast as those of the UK, but France managed to conquer half of Africa. It has never been a world hegemon, but it has always been one of the strongest nations.
France always swings between being a first-rate and a second-rate power, looking like it is falling behind but somehow emerging again, looking like it is rising but then somehow being suppressed.