The Franco-Prussian War arose nominally from the quarrel about the throne of Spain, to which a prince of the Hohenzollern house had put in a claim, first obtaining permission from Wilhelm I to accept the dignity. This prince, Leopold, was not a member of the Prussian {211} royal family, but he was a Prussian subject and a distant kinsman of the Kaiser. It was quite natural, therefore, that he should ask the royal sanction for his act and quite natural that Wilhelm should give it his approval if Spain made the offer of the crown. Napoleon sought some cause of difference with Prussia, because Bismarck had refused to help him to win Belgium and Luxemburg in 1869. He was jealous of this new military power, for his own fame was far outstripped by the feats of arms accomplished by the forces of General von Moltke, the Prussian general. He thought that war against his rival might help him to regain the admiration of the French. They were humiliated by the failure of the Mexican design and saw fresh danger for their country in Italian unity and the new confederation of North Germany. Napoleon, racked by disease, might have checked his own ambition if his Empress had not been too eager for a war. He was misled by Marshal Leboeuf into fancying that his own army was efficient enough to undertake any military campaign. He allowed his Cabinet to demand from Wilhelm I that Prince Leopold's claim to the Spanish crown, which had been withdrawn, should never be renewed by the sanction of Prussia at least. The unreasonable demand was refused, and France declared war in July 1870, eighteen years after the new empire had risen on the ruins of the Republic of the French. The other European powers would not enter this war, though England offered to mediate between the rival powers. France and Prussia had to test the strength of their armies without allies, and neither thought how terrible the cost would be of that long national jealousy. Napoleon took the field himself, leaving Eugenie as {212} Regent of the French, and the King of Prussia led his own army with General Von Moltke and General Von Roon in command. The French army invaded South Germany, but had to retreat in disorder after the battle of Worth. The battle of Sedan on September 1st, 1870, brought the war to a conclusion, the French being routed and forced to lay down their arms. Napoleon had fought with courage, but was obliged to surrender his sword to Wilhelm I upon the battlefield. He declared that he gave up his person only, but France herself was forced to yield after the capitulation of Metz, which had resisted Prussia stoutly. The Empress had fled to England and the Emperor had been deposed. France was once more a Republic when the siege of Paris was begun.