t he was defeated by French troops at the battle of Mentana.
The repulse of the Italian hero increased the national dislike of
French interference, but Napoleon only consented to evacuate Rome in
1870 when he had need of all his soldiers to carry out his boast that
he would "chastise the insolence of the King of Prussia."

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been withdrawn, should never be renewed by the sanction of Prussia at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 com