Bismarck unified Germany by manipulating leaders of multiple countries, which caused wars and gave the German people a common enemy and reason to unite under King William I. Bismarck even went so far as to manipulate messages from King William to the leaders in France and vice versa to ensure both parties felt wronged and insulted, leading to the Franco-Prussian war.
Bismarck used many tricks and ideas to circumnavigate and manipulate William I into doing what he wanted. When William I passed, he was succeeded by his son Frederick III and grandson William II. Bismarck was unable to use the same tactics with these men that he did with their predecessor. William II removed Bismarck from service, but Bismarck remained a symbol of power and war.