We measure the effects of a network of heroes in legitimizing and diffusing extreme political behaviors. Exploiting newly-declassified intelligence files, novel voting data and regimental histories, we show the home municipalities of French line regiments arbitrarily rotated through Philippe Pétain's command during the heroic WWI battle of Verdun, though similar before WWI, increasingly espouse Pétain's authoritarian political views thereafter, raising 7% more active Nazi collaborators per capita during the Pétain-led Vichy regime (1940-44). The effects are similar across joining Fascist parties, German forces, paramilitaries hunting Jews and the Resistance, and collaborating economically.