The Congress of Vienna had left Germany as a patchwork of small states, none of which were capable of exercising influence at a continental level. The idea of German unification had been a key theme in the revolutions of 1848–9, but never came to anything. However, as Austria began to become more powerful in the 1850s, the Prussian politician Otto von Bismarck began to agitate for the unification of Germany. He was convinced that only a united Germany would be able to stand up to the four Great Powers then dominating European affairs – Great Britain, France, Austria, and Russia.
A turning point was reached when Wilhelm I became king of Prussia in 1861. Wilhelm appointed Bismarck as both his president and foreign minister. Bismarck launched a war against Austria in 1866, in which a highly efficient Prussian army defeated its Austrian enemy. After annexing former Austrian territories, Prussia emerged as the dominant politi- cal and economic force in Germany. Realizing the threat this posed, France declared war on Prussia in July 1870. Seeing France as the aggressor, other German states rallied to Prus- sia’s support. The Prussian victory of 1871 set the scene for the reunification of Germany, with Wilhelm I as its emperor (German: Kaiser), and Bismarck as its chancellor.