To what extent can the values of nations be reshaped by heroes? We measure how an exogenous network of heroic individuals helped undermine democratic values and diffused support for autocracy in what was one of the world’s longest-lived republics- that of inter-war France. Having demonstrated through costly sacrifice their willingness to put the nation’s needs above their own, heroes are more likely to evoke trust on other national questions. This can leave them specially positioned to legitimize views previously considered deeply repugnant. Social networks of individuals sharing a heroic identity can further transmit and reinforce this influence, leading to escalating commitments that entrench political positions and make debiasing more difficult.