Despite the advantage of one side's Chassepot rifles in this conflict, that side got bogged down near the Saar River early in this war.  
Despite the advantage of one side's Chassepot rifles in this conflict, that side got bogged down near the Saar River early in this war.  Other engagements in this war saw the successive defeat of forces under Bazaine at the battles of Mars-la-Tour and Gravelotte.  As a consequence of this conflict, the Papal States were annexed by Italy and Alsace-Lorraine also changed hands in the Treaty of Frankfurt.  Prompted by the attempt to install Prince Leopold on the throne of Spain by Otto von Bismarck, it saw the decisive Battle of Sedan and led to the Paris Commune.  For 10 points, identify this conflict that saw the defeat of Napoleon III and the 2nd Empire.
Despite the advantage of one side's Chassepot rifles in this conflict, that side got bogged down near the Saar River early in this war.  
{Franco-Prussian} War (or {Franco-German} War or the {1870} War)