It is clear why Cavour wanted the alliance, but what benefits would France have from allying itself to a relatively weak (as far as I know) kingdom?
1Napoleon III was committed to Italian unification and Piedmont was the obvious leader of the unification movement. The help given by Piedmont in the Crimean War also must have been a factor.– Felix GoldbergFeb 22, 2014 at 19:34
@FelixGoldberg But why was he committed to Italian unification?– OviFeb 22, 2014 at 20:10
2en.wikipedia.org/wiki/…– Felix GoldbergFeb 22, 2014 at 22:15
@Ovi - Because having Italy unified would push Austria away from France.– OldcatAug 15, 2014 at 22:47
An alliance with the Sardinia-Piedmont was a good way to weaken the Austro-Hungarian Empire, and to win an potentially strong ally on the Alpine south-east border of France, betting on the unification of the Italian peninsula by the kingdom of Sardinia-Piedmont.
A weak Sardinia-Piedmont Kingdom meant that France could be threatened by an invasion from the Austro-Hungarian Empire through its Alps border with then Piedmont.
In return for its support to Piedmont-Sardinia, France received a significant amount of territory: the province of Savoy and the county of Nice.
This posture appears to have been particular to Napoleon III.
Previous French rulers preferred to capture pieces of Italy, specifically Piedmont and Lombardy, even if it meant dividing the country with the Hapsburgs (e.g. giving Austria Venice, or the "two Sicilies" to Spain. These rulers included Napoleon Bonaparte, and before him, several of the Kings Louis, and King Charles VIII.
Napoleon III preferred to "rule by proxy." He felt, quite reasonably as it turned out, that France's interests would be best served by having a united, but weak Italy as a "buffer zone" against the expansion of Austria-Hungary. To him, what could be gotten for France was less important than what could be kept away from others.
Ironically, Napoleon III also supported the candidacy of Maximilian (the brother of Austria Hungary's Franz Joseph) to be Emperor of Mexico as a check against the power of the United States. But his forces were defeated by the Mexicans at Puebla, May 5, 1862, and he "pulled" his support for Maximilian after the end of the Civil War, and the re-enforcement of the Monroe Doctrine, causing him to be executed by firing squad.
Because with Sardinia-Piedmont comes the House of Savoy, a powerful political and trade dynasty with far-reaching influence throughout Europe.
I am not sure that this is the right answer. Savoy was actually a minor power and Napoleon III apparently did not care not very much for dynastic considerations (he married for love). My comments to OP point at a more likelier explanation, imho. Feb 22, 2014 at 22:17
@FelixGoldberg - A minor power that also wound up with the united Italian throne, and kept it until the second world war. Much like the Habsburgs and Hanvovers, the Savoys were everywhere in European nobility. An alliance with their seat of power couldn't hurt, especially as a political marriage was out. Feb 23, 2014 at 15:38
But you forget one thing: it was Napoleon III who put the Savoy house on the Italian throne! You are arguing that an alliance with them was obvious because they were so awesome. But there awesomeness was gotten through the alliance, which means Napoleon must have had other reasons. Otherwise - why ally himself with them and not, say, Naples? Feb 23, 2014 at 18:09
@FelixGoldberg - the Savoyyards being in power places all over preceded the throne thing, IIRC– DVKFeb 24, 2014 at 19:55
@DVK Examples..? Apr 11, 2014 at 5:19