In the 1860s, the Empire no longer had the aura it had at its beginnings. Its loss of power abroad stemmed largely from its failed attempt to overthrow a republic and set up a Latin Empire in Mexico in favor of Archduke Maximilian of Austria in 1863. The Empire embarked on colonization experiences from 1861 to 1863 in Cochinchina and Annam. Similar inconsistencies were noticeable in the Emperor's European policy. The support he had given to the Italian cause had raised the hopes of other nations. The proclamation of the Kingdom of Italy on February 18, 1861 after the rapid annexation of Tuscany and the Kingdom of Naples had proven the danger of half measures. But when the concession, however limited, was made for the freedom of a nation, it could hardly be withheld for the no less legitimate aspirations of others.
In 1863 these "new rights" still demanded to be recognized:in Poland, in Schleswig and Holstein, in Italy, now obviously united but without frontiers or capitals, and in the principalities of the Danube. In order to extricate himself from the Polish impasse, the Emperor again had recourse to the expedient of Congress. It was once again unsuccessful, because it was inopportune:the United Kingdom even refused the principle of a congress, while Austria, Prussia and Russia only gave their adhesion on conditions which made it futile. that is to say, they set aside the vital questions of Veneto and Poland.
Thus Napoleon was yet to disappoint the hopes of Italy, let Poland be crushed, and allow Germany to triumph over Denmark in the question of Schleswig-Holstein.
He was helped by the end of the industrial crisis when the American Civil War ended, by the apparent resolution of the Roman question by the convention of September 15 which guaranteed the papal states the protection of Italy, and finally by the treaty of October 30, 1864 which temporarily ended the crisis of the Schleswig-Holstein question.
After 1865 the temporary agreement which had united Austria and Prussia for the administration of the conquered duchies gave rise to a silent antipathy. Although the Austro-Prussian War of 1866 was unexpected, its rapid conclusion was a severe shock to France. After the triumphant plebiscite of 1869, Emile Ollivier declared that “at no time has the maintenance of peace in Europe been so assured”. But after July 3, 1866 and the Battle of Sadowa, the Treaty of Prague put an end to the age-old rivalry between the Habsburgs and the Hohenzollerns for hegemony over Germany, which was an opportunity for France, and Prussia allowed himself to honor Napoleon's pretensions by establishing between his North German confederation and the southern states an illusory border along the Main. The unsuccessful efforts of the French emperor to obtain "compensation" on the left bank of the Rhine in exchange for the states of southern Germany, made matters worse. France realized with unpleasant surprise that on her eastern frontier had appeared a military power by which her influence, if not her existence, was threatened; that in the name of the principle of the sovereignty of nations, Germany had been united under the thumb of a dynasty by militaristic and aggressive tradition, by tradition enemy of France; that this new and threatening power had destroyed French influence in Italy, which owed the acquisition of Venetia to a Prussian alliance and Prussian arms; and that all this was due to Napoleon III, manipulated each time since his first meeting with Otto von Bismarck in Biarritz in October 1865. The latter, in order to make the reunification of Germany definitive, needed a common enemy to unite the German peoples:it will be France.