The Franco-Prussian War was the final stage in German unification. Now nationalistic fever also seized people in Germany.The catured French place of Versallies, King Wilhelm I of Prussia was crowned Kaiser or emeperor.
Bismarck was an expert at manufacturing "incidents" to gain his ends. He created the impression that the French ambassador had insulted the Prussian King. The French reacted to Bismarcks deception by declaring war on Prussia.
a few southern German states remained indepent of Prussian control. The majority of southern Germans were Catholics. Mant in the region resisted domination by a protestant Prussia.