The French Army crumbled swiftly under the powerful blows delivered to it in 1940 by Adolf Hitler's self-confident Wehrmacht. Launching a massive feint into Belgium to lure mobile French armies and the British Expeditionary Force (BEF) away from the actual point of attack, the weakly protected Ardennes Forest, the Germans struck past the Maginot Line. In a lightning campaign, Guderian's panzers punched through to the coast, dividing Allied forces with a steel cordon across France and forcing the evacuation of the BEF from the port of Dunkirk.

Not all French people proved willing to surrender to the Nazi invaders, however. While large numbers collaborated – working for German or Vichy companies to provide for themselves or their families – and some wholeheartedly backed the new regime out of opportunism, fascist conviction, or other motivations, a courageous minority operated in secret to resist their conquerors and the quisling state at Vichy: "De Gaulle described them as being bound together by a taste for risk and adventure [...] national pride sharpened by the suffering of their nation and 'an overwhelming confidence in the strength and cunning of their own plot'. [...] 'With him, it is [...] serving the Resistance and national honour, uncompromisingly demanding,' wrote one. 'With him, we would have to get used to breathing the rarefied air of the summits.'" (Fenby, 2012, 109).

The French Resistance never grew into a single unified organization. Rather, it remained divided in several major and numerous minor factions, each with their own philosophy and agenda. While these factions all shared the same goal – opposition to the Germans their Vichy pawns – they viewed each other with some suspicion and sometimes cooperated only grudgingly.

During the war years, however, the Resistance kept the spirit of an independent and defiant France smoldering under the surface of Nazi domination, waiting for the opportunity to emerge again, regardless of the precise political beliefs of its members.

Though exaggerated in scope and effectiveness by postwar legends seeking to minimize the widespread (usually involuntary) collaboration among the French people, the Resistance actually embodied a patriotic spirit determined to defeat Nazi totalitarianism and make France once again the nation of "liberté, égalité, fraternité" under the tricolor flag. Despite the faults, foibles, and occasional cruelty or criminality of individual Resistance members, the shared goal of defeating Nazi authoritarianism provided the glue needed to more or less unify the disparate factions. This defining aim also gave the movement resilience to weather the brutal suppression meted out by the Gestapo, the infamous Klaus Barbie, and the Vichy Milice.