An Austrian-Prussian rivalry, starting in the 1700s, had led to the Austro-Prussian War of July/August 1866. Immediate causes for the war had been the unsettled question of Slesvig-Holstein (which Prussia intended to annex) and a reform of the German Confederation. After a victory in summer 1866, agreements with Austria and France allowed Prussia to reshape the political landscape in Northern Germany (north of the river Main). The leading politician of Prussia was minister president Otto von Bismarck, serving under king William I.