Franco-German hostility spanned centuries, rooted in structural rivalry:
Alsace-Lorraine changed hands repeatedly: Holy Roman Empire → France (1648, 1766) → Germany (1871) → France (1919) → Germany (1940) → France (1945). Each transfer fueled irredentism.
Post-1871, unified Germany's rapid industrialization (steel, chemicals, railways) challenged French economic dominance. Rivalry over colonies, markets, and resources (Lorraine iron, Ruhr coal).
Mutual caricatures: French saw Germans as rigid, militaristic, humorless; Germans saw French as decadent, chaotic, expansionist. Reinforced by propaganda, education, media.
From "hereditary enemies" to core of European unity—a unique historical reversal.