In this famous image by Professor Wilhelm Camphausen, Bismarck is conversing with Napoleon III after the French Emperor was captured at the Battle of Sedan on September 2, 1870.
Two months earlier, in July 1870, on the tenuous pretext of opposing a Hohenzollern appointment to the throne of Spain, the French Empire declared war on Prussia, beginning the Franco-Prussian War.
Unfortunately for France, throughout the 1860s Prussia had built a modern, mobile army under the steady leadership of von Moltke and Albrecht von Roon. Then the newly modernized army was tested and honed to perfection during the war with Austria in 1866. So in July 1870, the Prussians led their German allies into France with a powerful and remarkably professional military. The French suffered a staggering series of defeats until September 2, 1870, when the French army was routed at the Battle of Sedan, and Napoleon III himself was captured. Two days later, the French parliament deposed him and declared the Third Republic.
After Sedan, the new Third Republic refused to surrender, leading to many more deaths and a great deal of destruction as their new armies suffered a series of defeats. The capital city of Paris was put under siege by setting up a blockade, but was not put under bombardment due to moral grounds, but the blockade served its purpose and after 3 months the city surrendered. An armistice was signed at Versailles in January, 1871. Thereafter the starving population of Paris was fed by delivering railway cars full of German Army provisions. Northern France was temporarily occupied by Prussia until a treaty was concluded in May. Besides reparations, the German speaking provinces of Alsace and Lorraine were returned to Germany after 195 years of occupation by France.
Using the prevailing German nationalist feelings to his advantage, Bismarck formalized the establishment of a new German Empire, which was officially declared in the occupied Palace of Versailles, further emphasizing that France was no longer the leading military power in Europe.
Meanwhile, defeated and deposed, and having led his country to ruin, Napoleon III went into exile in Britain. He died there two years later on January 9, 1873.
The quick German victory over the French stunned neutral observers, many of whom had expected a French victory and most of whom had expected a long war. The strategic superiority of the Prussians was not appreciated outside Germany until after hostilities had ceased. Other countries quickly discerned the advantages of the Prussian military system, and adopted many of their innovations, particularly the existence of a General Staff, merit based promotion of officers, universal conscription and highly detailed mobilization systems.