In July 1870 France again went to war. Defeat led to the collapse of the regime. The report of the subsequent commission of enquiry began the construction of a myth, which blamed the disaster entirely on the Emperor and a small number of generals. Napoleon, Marshal Bazaine, and the military intendancy were the most convenient scapegoats. The official history of the war, which followed, obeyed ministerial instructions to present only such facts as enhanced the army's reputation. Napoleon III, so despised by republicans as ‘the man of 2 December’, had now achieved infamy as ‘the man of Sedan.’ The purpose of this chapter might be defined, reversing the order of Marx's words, as to ‘demonstrate how the class struggle in France created circumstances and relationships that made it possible for a hero to play a grotesque mediocrity's part’. Rather than apportioning blame, however, the historian's task is to achieve understanding. The questions seem clear enough. What were the regime's foreign policy objectives? To what extent were they achieved and with what consequences both for France and international relations? What were the inter-relationships between internal and external politics? Given a predilection for high-risk strategies, which had already led to war on two occasions, how well prepared was the French army? Why was the decision to go to war taken in 1870? Why were the French defeated and why did the regime collapse?