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The Plombières Agreement (, ) of 21 July 1858 was a secret verbal agreement which took place at Plombières-les-Bains between the chief minister of Piedmont-Sardinia,
Camillo Benso, Count of Cavour Camillo Paolo Filippo Giulio Benso, Count of Cavour, Isolabella and Leri (; 10 August 1810 – 6 June 1861), generally known as the Count of Cavour ( ; ) or simply Cavour, was an Italian politician, statesman, businessman, economist, and no ...
, and the French Emperor,
Napoleon III Napoleon III (Charles-Louis Napoléon Bonaparte; 20 April 18089 January 1873) was President of France from 1848 to 1852 and then Emperor of the French from 1852 until his deposition in 1870. He was the first president, second emperor, and last ...
. Some older English sources refer to it as the Treaty of Plombières. In modern times, it is merely referred to as an "agreement", since nothing was signed. Based on limited available evidence, there have been disputes on the details of what was agreed upon at the meeting, but as years passed it became apparent that the agreement had opened the way for the , on 28 January 1859, and for the
Second Italian War of Independence The Second Italian War of Independence, also called the Sardinian War, the Austro-Sardinian War, the Franco-Austrian War, or the Italian War of 1859 (Italian: ''Seconda guerra d'indipendenza italiana''; German: ''Sardinischer Krieg''; French: ...
that became a vital step towards
Italian unification The unification of Italy ( ), also known as the Risorgimento (; ), was the 19th century political and social movement that in 1861 ended in the annexation of various states of the Italian peninsula and its outlying isles to the Kingdom of ...
, which was achieved within a decade of the agreement. The Plombières Agreement was an agreement concerning a future war in which
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
and
Piedmont Piedmont ( ; ; ) is one of the 20 regions of Italy, located in the northwest Italy, Northwest of the country. It borders the Liguria region to the south, the Lombardy and Emilia-Romagna regions to the east, and the Aosta Valley region to the ...
would ally themselves against
Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...
to remove and exclude Austrian influence from the Italian peninsula. In its place, Italy, which
Klemens von Metternich Klemens Wenzel Nepomuk Lothar, Prince of Metternich-Winneburg zu Beilstein ( ; 15 May 1773 – 11 June 1859), known as Klemens von Metternich () or Prince Metternich, was a German statesman and diplomat in the service of the Austrian Empire. ...
, a previous Austrian chancellor, had reportedly dismissed on various occasions as a "
ere Ere or ERE may refer to: * ''Environmental and Resource Economics'', a peer-reviewed academic journal * ERE Informatique, one of the first French video game companies * Ere language, an Austronesian language * Ebi Ere (born 1981), American-Nigeria ...
geographical expression", would be divided into two spheres of influence to be dominated respectively by Piedmont and France. As events turned out, the war was triggered as agreed at Plombières, but its geopolitical aftermath was not precisely the one that had been envisaged.


The French position

Emperor
Napoleon III Napoleon III (Charles-Louis Napoléon Bonaparte; 20 April 18089 January 1873) was President of France from 1848 to 1852 and then Emperor of the French from 1852 until his deposition in 1870. He was the first president, second emperor, and last ...
was keen to settle the "Italian question" and to revise the humiliations of the 1815
Congress of Vienna The Congress of Vienna of 1814–1815 was a series of international diplomatic meetings to discuss and agree upon a possible new layout of the European political and constitutional order after the downfall of the French Emperor Napoleon, Napol ...
. He had long ago formed the view that this required a war against
Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...
. War with Austria could bring France military success, delivering glory to France and humiliation to Austria. Actively supporting Italian nationalist aspirations would place
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
firmly on the side of what was then seen as progressive liberalism, and confirm the nation's special revolutionary credentials. For France, however, Italian independence and Italian political unification were two very different things. Political unification would have been contrary to French interests because it would have risked reducing French influence on the Italian peninsula.


Count of Cavour's opportunity

The prime minister of Piedmont-Sardinia,
Camillo Benso, Count of Cavour Camillo Paolo Filippo Giulio Benso, Count of Cavour, Isolabella and Leri (; 10 August 1810 – 6 June 1861), generally known as the Count of Cavour ( ; ) or simply Cavour, was an Italian politician, statesman, businessman, economist, and no ...
, was aware of the French objectives and was looking for an opportunity to serve these, while simultaneously achieving his goal of lifting the oppressive burden of Austrian rule from as many Italians as possible The arrival in
Turin Turin ( , ; ; , then ) is a city and an important business and cultural centre in northern Italy. It is the capital city of Piedmont and of the Metropolitan City of Turin, and was the first Italian capital from 1861 to 1865. The city is main ...
of Jacques Alexandre Bixio in April 1858 provided Cavour with his opportunity. Bixio was a retired physician, originally from
Liguria Liguria (; ; , ) is a Regions of Italy, region of north-western Italy; its Capital city, capital is Genoa. Its territory is crossed by the Alps and the Apennine Mountains, Apennines Mountain chain, mountain range and is roughly coextensive with ...
, with a taste for politics and ballooning: he had made his life in France. Bixio was a friend both of Cavour and of Prince Napoléon-Jérôme Bonaparte, cousin to the French Emperor. His presence in Turin was ostensibly part of a discrete European tour, visiting various European royal families to find a socially suitable wife for the Emperor's cousin. Bixio was also able to pass to his friend, the Piedmontese chief minister, French proposals for an alliance of the two states against Austria. The agreement would be reinforced through the marriage of
Princess Maria Clotilde of Savoy Maria Clotilde of Savoy (Ludovica Teresa Maria Clotilde; 2 March 1843 – 25 June 1911) was born in Turin to Vittorio Emanuele II, later King of Italy and his first wife, Adelaide of Austria. She was the wife of Prince Napoléon-Jérôme Bonapa ...
, daughter of the Piedmontese king,
Victor Emmanuel II Victor Emmanuel II (; full name: ''Vittorio Emanuele Maria Alberto Eugenio Ferdinando Tommaso di Savoia''; 14 March 1820 – 9 January 1878) was King of Sardinia (also informally known as Piedmont–Sardinia) from 23 March 1849 until 17 March ...
, to Prince Napoléon Bonaparte. Reflecting the international sensitivities involved, negotiations progressed outside the "usual" diplomatic channels. To confirm his approval of the proposal, Cavour sent his diplomat, Costantino Nigra, to Paris, where Nigra made contact with another friend and confidant of the Emperor (and another physician) called Henri Conneau. On 9 May 1858, Conneau was able to confirm to Nigra that the alliance proposal had the full support of the Emperor himself. Further talks now took place in Turin involving Conneau, Cavour, and King Victor Emmanuel. At this point, a suggestion came from the Emperor for a meeting between himself and Cavour at Plombières-les-Bains, a fashionable health resort in the small ravine of in the
Vosges The Vosges ( , ; ; Franconian and ) is a range of medium mountains in Eastern France, near its border with Germany. Together with the Palatine Forest to the north on the German side of the border, they form a single geomorphological unit and ...
, reassuringly far from Paris or Turin, and off the beaten track of those following international diplomacy and politics.


The meeting

On 11 July 1858 Count Cavour left Turin, letting it be known that he was heading for Switzerland. Only the King and the Piedmontese military commander, General La Marmora, were aware that his final destination was Plombières, where nine days later the Piedmontese prime minister arrived on the evening of 20 July 1858. There is no surviving source for the meeting from Napoleon III. The only direct report of the discussions comes from Cavour. Cavour's report takes the form of a letter that he wrote to the King on 24 July 1858 from an overnight halt at
Baden-Baden Baden-Baden () is a spa town in the states of Germany, state of Baden-Württemberg, south-western Germany, at the north-western border of the Black Forest mountain range on the small river Oos (river), Oos, ten kilometres (six miles) east of the ...
, while on his way home. This letter was made public in 1883 in '' La Perseveranza'', a Milanese newspaper. The meeting itself took place on 21 July 1858, with a first four-hour session starting at 11:00 and a second session running from 16:00 until 20:00. It was a Tuesday. The venue was a moving one: the two men sat together, without support staff, in a small horse-drawn carriage as it undertook a slow passage round and round the little town.


Searching for a ''casus belli''

Neither man wanted the blame for causing the impending war. Cavour noted that Napoleon began by stating that he was determined to support Piedmont-Sardinia with all his strength in a war against Austria, on the condition that the war was not in support of a revolutionary cause and could be justified in diplomatic terms and, more importantly, before public opinion in France and in Europe. Violations of trade treaty obligations by Austria were considered by Napoleon to be insufficient grounds for a war. There was discussion of whether the presence of an Austrian military garrison in
Bologna Bologna ( , , ; ; ) is the capital and largest city of the Emilia-Romagna region in northern Italy. It is the List of cities in Italy, seventh most populous city in Italy, with about 400,000 inhabitants and 150 different nationalities. Its M ...
(in the
Papal States The Papal States ( ; ; ), officially the State of the Church, were a conglomeration of territories on the Italian peninsula under the direct sovereign rule of the pope from 756 to 1870. They were among the major states of Italy from the 8th c ...
) might justify war against Austria, but the French Emperor was in the end reluctant to use this as a pretext. There were Austrian troops not only in Bologna, but also in
Rome Rome (Italian language, Italian and , ) is the capital city and most populated (municipality) of Italy. It is also the administrative centre of the Lazio Regions of Italy, region and of the Metropolitan City of Rome. A special named with 2, ...
and the
Papal States The Papal States ( ; ; ), officially the State of the Church, were a conglomeration of territories on the Italian peninsula under the direct sovereign rule of the pope from 756 to 1870. They were among the major states of Italy from the 8th c ...
, preserving the status quo; in Rome, there were also French troops for broadly similar reasons, and parallels between the garrisoning of Bologna and of Rome were uncomfortably close. It then transpired that Napoleon had a proposal of his own. The
Duchy of Modena and Reggio The Duchy of Modena and Reggio (; ; ) was an Italian state created in 1452 located in Northern Italy, Northwestern Italy, in the present day region of Emilia-Romagna. It was ruled since its establishment by the noble House of Este, and from 1814 ...
presented a more promising ''
casus belli A (; ) is an act or an event that either provokes or is used to justify a war. A ''casus belli'' involves direct offenses or threats against the nation declaring the war, whereas a ' involves offenses or threats against its ally—usually one bou ...
''. Its ruler was Francis V, an Austrian ally and one of the many great-grandsons of the eighteenth-century Empress
Maria Theresa Maria Theresa (Maria Theresia Walburga Amalia Christina; 13 May 1717 – 29 November 1780) was the ruler of the Habsburg monarchy from 1740 until her death in 1780, and the only woman to hold the position suo jure, in her own right. She was the ...
. Francis had decided not to acknowledge Napoleon III as emperor of France following the latter's
coup d'état A coup d'état (; ; ), or simply a coup , is typically an illegal and overt attempt by a military organization or other government elites to unseat an incumbent leadership. A self-coup is said to take place when a leader, having come to powe ...
at the start of the decade. Francis of Modena had inadvertently set himself up as eminently dispensable in the eyes of Napoleon. As they traveled round the streets of Plombières, Cavour and Napoleon devised a plan to provoke an appeal for protection from the Modenese citizens to the king of Piedmont-Sardinia, and a demand for the annexation of their duchy to Piedmont-Sardinia. The co-operation of the Modenese citizenry in such a scheme seems never to have been in doubt. The king of Piedmont-Sardinia would respond by graciously declining the appeal in the terms in which it was put, but he would nevertheless send a threatening communication to Francis V of Modena. The communication would be seen as interference in the Austrian sphere of influence and would provoke outrage in Vienna. As such, Austria's response would be correspondingly provocative. Piedmont-Sardinia would then find itself obliged to occupy Massa, a coastal city and an important port belonging to the Duchy of Modena, by which time a wider war with Austria would have been triggered.


A political structure for Italy

Napoleon III stated that the Austrians must be completely ejected from the Italian peninsula, and Cavour agreed. The discussion then moved on to agreement on a political structure for the Italian peninsula following the removal of Austria. * The existing Kingdom of Piedmont-Sardinia, together with the agriculturally rich
Po Valley The Po Valley, Po Plain, Plain of the Po, or Padan Plain (, , or ) is a major geographical feature of northern Italy. It extends approximately in an east-west direction, with an area of including its Venetian Plain, Venetic extension not actu ...
to the
Soča Soča (, in Slovene) or Isonzo (, in Italian; other names: ; ; or ') is a long river that flows through western Slovenia () and northeastern Italy (). An Alpine river in character, its source lies in the Trenta Valley in the Julian Alps ...
river, and along with the entire northern (
Romagna Romagna () is an Italian historical region that approximately corresponds to the south-eastern portion of present-day Emilia-Romagna, in northern Italy. Etymology The name ''Romagna'' originates from the Latin name ''Romania'', which originally ...
) part of the Papal States (the so-called "
Papal Legations The delegations as they existed in 1859 Between the Congress of Vienna (1815) and the capture of Rome (1870), the Papal State was subdivided geographically into 17 apostolic delegations (''delegazioni apostoliche'') for a ...
"), would become the Kingdom of Upper Italy ("''Alta Italia''"), under the king of Piedmont-Sardinia ("''...sotto la guida di Vittorio Emanuele''"). * The southern part of the Papal States, with the exception of Rome and its immediate surrounds, was to be merged with the
Grand Duchy of Tuscany The Grand Duchy of Tuscany (; ) was an Italian monarchy located in Central Italy that existed, with interruptions, from 1569 to 1860, replacing the Republic of Florence. The grand duchy's capital was Florence. In the 19th century the population ...
in order to create a Kingdom of Central Italy ("''Regno dell’Italia centrale''"). The grand duke of Tuscany, Leopold II, another Austrian ally and great-grandson of Maria Theresa, would need to go. He would be replaced, at least on a provisional basis, by the (originally Francophone) Duchess of Parma Louise Marie of Artois. Napoleon had domestic reasons for displaying magnanimity to a descendant of the former Bourbon ruling dynasty: the appeal of traditional monarchism was far from dead in France. * Rome and its immediate surroundings would continue to be ruled by the Pope. * Further south, the
Kingdom of the Two Sicilies The Kingdom of the Two Sicilies () was a kingdom in Southern Italy from 1816 to 1861 under the control of the House of Bourbon-Two Sicilies, a cadet branch of the House of Bourbon, Bourbons. The kingdom was the largest sovereign state by popula ...
should remain under the control of its existing king, Ferdinand II. Were Ferdinand to be removed from the scene the Emperor would be very happy for his successor to be his relative, Prince Lucien Murat. (Ferdinand II was known to be unwell: he would die within a year.) These four Italian states would have formed a confederation, modeled on the
German Confederation The German Confederation ( ) was an association of 39 predominantly German-speaking sovereign states in Central Europe. It was created by the Congress of Vienna in 1815 as a replacement of the former Holy Roman Empire, which had been dissolved ...
, of which the honorary presidency would be given to the Pope.


The French price

As Cavour later reported to his king, :"The Emperor asked me what France would get in return for her military backing, and whether Your Majesty would hand over
Savoy Savoy (; )  is a cultural-historical region in the Western Alps. Situated on the cultural boundary between Occitania and Piedmont, the area extends from Lake Geneva in the north to the Dauphiné in the south and west and to the Aosta Vall ...
and
Nice Nice ( ; ) is a city in and the prefecture of the Alpes-Maritimes department in France. The Nice agglomeration extends far beyond the administrative city limits, with a population of nearly one million :Napoleon now stroked his moustache and indicated that these nationality issues were perhaps not quite such a priority for now. The political future of Nice could be settled on another occasion. He moved on to how the alliances might line up in a future war. British neutrality could be secured with the help of Piedmontese diplomacy,
Prussia Prussia (; ; Old Prussian: ''Prūsija'') was a Germans, German state centred on the North European Plain that originated from the 1525 secularization of the Prussia (region), Prussian part of the State of the Teutonic Order. For centuries, ...
would abstain despite an adversarial perspective in respect to Austria, and
Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
would abstain albeit from a pro-Austrian position. On the matter of force levels for the war, the Piedmontese military commander Alfonso Ferrero La Marmora had produced a plan involving an army of 160,000 men, provided 50:50 by France and Piedmont-Sardinia, and a military campaign focused on the Po Valley. The emperor had his plan, however, involving 300,000 men of whom 200,000 would be French, and he spoke in terms of a military campaign pushing right through to
Vienna Vienna ( ; ; ) is the capital city, capital, List of largest cities in Austria, most populous city, and one of Federal states of Austria, nine federal states of Austria. It is Austria's primate city, with just over two million inhabitants. ...
.


The dynastic marriage

After a mid-afternoon break, the two climbed back into their little carriage around five o'clock. The Emperor turned to the proposed marriage between his cousin, Prince Napoléon Bonaparte, with Victor Emmanuel's eldest daughter. Cavour had already been fully briefed by his king on this matter. He highlighted the unfortunate rumours in circulation about the character of Prince Napoléon Bonaparte and also drew attention to the age of the Princess, who was only fifteen. In the report he wrote to the King three days after the meeting, Cavour was nevertheless keen to stress the merits of the proposed marriage. The nature of future political and military alliances would be transformed if created without the underpinning of the marriage on which Napoleon was so keen. Progressing the alliance without marriage would be an enormous political error. The meeting ended with a handshake, accompanied by the Emperor's injunction: "Have faith in me, as I have faith in you."


Objectives

It appears from Cavour's report of the meeting that Napoleon III had prepared very carefully for it, and dictated the terms of the secret "Plombières Agreement" that resulted. Piedmont-Sardinia might be a regional power in terms of the Po Valley, but France was a European
great power A great power is a sovereign state that is recognized as having the ability and expertise to exert its influence on a global scale. Great powers characteristically possess military and economic strength, as well as diplomatic and soft power ...
. Nevertheless, Cavour was entirely upbeat over the agreement.''"Ho lasciato Plombières coll’animo più sereno. Se il Re consente al matrimonio, ho la fiducia, dirò quasi la certezza, che fra due anni tu entrerai a Vienna a capo delle nostre file vittoriose."'' Count Cavour (23/24 July 1858) concluding his report from his transit halt at Baden-Baden to the king. The tensions between the disparate objectives and expectations of the parties are nevertheless clear. Cavour believed that by controlling "''Italia Alta''", the Northern Italian Kingdom, Piedmont-Sardinia would have practical political and economic control over the entire Italian peninsula. In contrast, Napoleon was convinced that France would have control over the southern two-thirds of Italy and would thereby be able to exercise de facto control over Piedmont-Sardinia. They could not both be right.


Consequences


The Franco-Sardinian Treaty

The treaty creating a was signed on 28/29 January 1859 at
Turin Turin ( , ; ; , then ) is a city and an important business and cultural centre in northern Italy. It is the capital city of Piedmont and of the Metropolitan City of Turin, and was the first Italian capital from 1861 to 1865. The city is main ...
by Victor Emmanuel II and at
Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
on 26 January 1859 by Napoleon III. Not everything agreed verbally at Plombières six months before surfaced in the treaty: it was silent on the geopolitical understandings covering central and southern Italy. On the military side, The treaty merely committed France to intervene alongside Piedmont-Sardinia in the event of aggression from Austria. In the event of any military events ending with the creation of a Kingdom of "''Alta Italia''", the northern Italian kingdom envisaged at Plombières, France would be rewarded, receiving Savoy and Nice. On 30 January 1859, the marriage of Prince Napoléon Bonaparte and Princess Maria Clotilde of Savoy was celebrated at Turin.


The war

Following a series of provocative military movements near the Austro-Piedmontese frontier by Piedmont-Sardinia, and having become aware of the Franco-Sardinian alliance, the Austrians took the initiative by issuing the Ultimatum of Vienna on 23 April 1859. The Austrian ultimatum required the total demobilisation of the
Royal Sardinian Army The Royal Sardinian Army (also the Sardinian Army, the Royal Sardo-Piedmontese Army, the Savoyard Army, or the Piedmontese Army) was the army of the Duchy of Savoy and then of the Kingdom of Sardinia, which was active from 1416 until it became t ...
. By failing to comply with this demand, the Piedmontese triggered a declaration of war by Austria, thereby fulfilling the French condition that their support for Piedmont-Sardinia would be contingent on Austria being the aggressor in any war. A succession of serious regional anti-Austrian pro-nationalist insurrections now broke out in Tuscany, Modena,
Parma Parma (; ) is a city in the northern Italian region of Emilia-Romagna known for its architecture, Giuseppe Verdi, music, art, prosciutto (ham), Parmesan, cheese and surrounding countryside. With a population of 198,986 inhabitants as of 2025, ...
and the Papal States. Napoleon III concluded that his earlier plan to secure French domination of central and southern Italy through his alliance with Piedmont-Sardinia could only be achieved at an unacceptable military and economic cost. On a personal level, he seems to have been genuinely (and very publicly) horrified by the slaughter involved in fighting wars in an industrial age, notably at the battles of
Magenta Magenta () is a purple-red color. On color wheels of the RGB color model, RGB (additive) and subtractive color, CMY (subtractive) color models, it is located precisely midway between blue and red. It is one of the four colors of ink used in colo ...
and
Solferino Solferino ( Upper Mantovano: ) is a small town and municipality in the province of Mantua, Lombardy, northern Italy, approximately south of Lake Garda. It is best known as being close to the site of the Battle of Solferino on 24 June 1859, part ...
. He was also aware of the risk to French security from an ambitious and opportunistic
Prussia Prussia (; ; Old Prussian: ''Prūsija'') was a Germans, German state centred on the North European Plain that originated from the 1525 secularization of the Prussia (region), Prussian part of the State of the Teutonic Order. For centuries, ...
in the event of France becoming over-committed militarily in Italy. He, therefore, hastened to sign an armistice with Austria. The French and the Austrians signed the Armistice of Villafranca without consulting the Piedmontese, provoking outrage and rioting in the streets of Turin. Under the terms agreed at Villafranca between France and Austria, most of
Lombardy The Lombardy Region (; ) is an administrative regions of Italy, region of Italy that covers ; it is located in northern Italy and has a population of about 10 million people, constituting more than one-sixth of Italy's population. Lombardy is ...
was transferred from Austria to France. France immediately transferred these territories to Piedmont-Sardinia, receiving Savoy and Nice in return. This left the central Italian states, notably
Tuscany Tuscany ( ; ) is a Regions of Italy, region in central Italy with an area of about and a population of 3,660,834 inhabitants as of 2025. The capital city is Florence. Tuscany is known for its landscapes, history, artistic legacy, and its in ...
and the Papal States, to be returned to the control of their former Austrian client-rulers. However, these central Italian territories were now occupied by Piedmontese troops who showed no enthusiasm for the idea of restoring Austrian-sponsored rulers. The French themselves had no wish or incentive to provide practical military or other support to the Austrians for such a restoration in defiance of their alliance with Piedmont. In practical terms, therefore, following the so-called
Second Italian War of Independence The Second Italian War of Independence, also called the Sardinian War, the Austro-Sardinian War, the Franco-Austrian War, or the Italian War of 1859 (Italian: ''Seconda guerra d'indipendenza italiana''; German: ''Sardinischer Krieg''; French: ...
, the Piedmontese retained control of both Italia Alta, the northern Italian kingdom agreed at Plombières, and of central Italy; paving the way for
Italian unification The unification of Italy ( ), also known as the Risorgimento (; ), was the 19th century political and social movement that in 1861 ended in the annexation of various states of the Italian peninsula and its outlying isles to the Kingdom of ...
to be fully realized twelve years later.


References

{{DEFAULTSORT:Plombieres Agreement Foreign relations of France Foreign relations of Italy 1858 in France 1858 in Italy France–Italy relations Second French Empire Italian unification History of Savoy Kingdom of Sardinia Territorial evolution of France Second Italian War of Independence Secret treaties