This chapter outlines Russia's involvement in the First World War, concentrating on the specific ways in which it caused the end of the old regime. It focuses on explaining the more specific political end point of regime change when the tsar abdicated and representatives of the national parliament, in consultation with representatives of worker and soldier councils, formed a new provisional government. The first proximate cause, the bread shortage in Petrograd, is inextricably linked to a larger question about the significance of relative Russian economic backwardness as an underlying cause of the revolution. Patriotic motives much less equivocally lay at the core of an explanation of the actions of the army commanders during the February crisis. The crucial turning point in the rise of the political opposition was the abandonment of the 'internal peace' and the creation of a united opposition to the government in the form of the 'Progressive Bloc' a broad coalition of parties in the Duma.