This rise of Prussia's power and influence disturbed and displeased, among all the European states, none more than France. It was only a few years before Napoleon III saw himself forced, partly through internal difficulties and partly through his failures in Mexico and Italy, to challenge William I of Prussia. In this combat the predominancy in German affairs was no longer at stake, as it had been between Prussia and Austria; but so powerful had Prussia become that France felt it necessary to defend the leadership in Central European affairs which it then claimed. The revolution which had broken out in 1868 in Spain and resulted in the expulsion of Queen Isabella became the indirect cause of the Franco-Prussian War. After various unsuccessful attempts on the part of Spanish statesmen to find a king for their country among the European princes they offered the crown of Spain to Prince Leopold of Hohenzollern-Sigmaringen, a relative of the King of Prussia. Naturally the prospect of having a German prince rule its western neighbor greatly excited France and led immediately to a strong protest on its part. But not satisfied with this Napoleon demanded from King William a promise that he should at no time permit his cousin to accept the Spanish throne. These demands of the French were promptly refused by the King of Prussia, and Bismarck and Von Moltke saw to it that the message as delivered was brusque and calculated to excite France to anger. Indeed, opinion was so deeply stirred that Napoleon felt compelled to ask for a declaration of war. On July 19, 1870, this step was taken. Undoubtedly Napoleon was influenced in his decision by his expectation that the south German states would either side openly with him or else at least refuse to side with Prussia, basing this hope on their fear that if Prussia should become all powerful in Germany their own independence would be threatened. His expectations, however, were not realized. As much through the wonderful statesmanship of Bismarck, who knew when to give as well as when to take, as through the awakening of an immensely strong national feeling throughout the length and breadth of Germany, the south Bavarian states, within a few days after France had declared war, sided openly with Prussia. This combination proved too strong for France, for it was superior not only in numbers and equipment, but especially in leadership. The unified German armies won battle after battle in quick succession and by September 2, Napoleon found himself with a large army hopelessly surrounded in Sedan and was forced to surrender. He was sent to Germany as a prisoner of war and his downfall resulted in the end of the Second Napoleonic Empire and the declaration of the Third French Republic.