Königgrätz (or Sadowa, as it is often called) decided the whole
campaign. The invaders now advanced rapidly towards Vienna, and at the
town of Nikolsburg concluded the Preliminaries of Peace with Austria
(July 26), whereupon a mandate came from Paris, bidding them stop. In
fact, the Emperor of the French offered his intervention in a manner
most threatening to the victors. He sought to detach Italy from the
Prussian alliance by the offer of Venetia as a left-handed present from
himself--an offer which the Italian Government subsequently refused.

To understand how Napoleon III. came to change front and belie his
earlier promises, one must look behind the scenes. Enough is already
known to show that the Emperor's hand was forced by his Ministers and by
the Parisian Press, probably also by the Empress Eugénie. Though
desirous, apparently, of befriending Prussia, he had already yielded to
their persistent pleas urging him to stay the growth of the Protestant
Power of North Germany. On June 10, at the outbreak of the war, he
secretly concluded a treaty with Austria, holding out to her the
prospect of recovering the great province of Silesia (torn from her by
Frederick the Great in 1740) in return for a magnanimous cession of
Venetia to Italy. The news of Königgrätz led to a violent outburst of
anti-Prussian feeling; but Napoleon refused to take action at once, when
it might have been very effective.

The best plan for the French Government would have been to send to the
Rhine all the seasoned troops left available by Napoleon III.'s
ill-starred Mexican enterprise, so as to help the hard-pressed South
German forces, offering also the armed mediation of France to the
combatants. In that case Prussia must have drawn back, and Napoleon III.
could have dictated his own terms to Central Europe. But his earlier
leanings towards Prussia and Italy, the advice of Prince Napoleon