German unification under Prussian supremacy became the main objective of Bismarck's policies, either through diplomatic or military means. He was known as the Iron Chancellor and his tremendous willpower led to the great period of German militarism. In 1867 he proclaimed the Constitution of the German Confederation of the North, as if it were a federal state, with Wilhelm I of Prussia as president and himself as Chancellor. After a series of agreements with the southern German states, in 1871 Bismarck proclaimed the Second Reich and the confederation of German states with Wilhelm I as Emperor or Kaiser of Germany. The idea of pan-Germanism took root and German territorial expansion was set in motion. This aspiration of achieving central European economic unity under its hegemony eventually took Germany into the First World War. After her defeat and the republican period, nationalist sentiment reappeared and reached its peak under Adolph Hitler and his National-Socialism which ended in another war, the Second World War.