The Annexation Of Austrian Territory By Italy In 1866

In 1866, the Kingdom of Italy and the Austrian Empire signed the Treaty of Vienna, which concluded the Third War of Italian Independence. The treaty confirmed the terms of the 12 August Armistice of Cormons, resulting in the transfer of Venetia and most of Friuli to the French Empire, who then gave the region to Italy after the consent of the inhabitants through a referendum. This represented the final division of the Habsburg-ruled Kingdom of Lombardy–Venetia, as the Lombard half had been ceded to the Kingdom of Sardinia in the earlier 1859 Treaty of Zurich. The territory of Venetia included modern Veneto, parts of Friuli and the city of Mantua.

The annexation of Venetia and Friuli

The Italian government had signed a military alliance with Prussia on April 8, 1866, through the mediation of French Emperor Napoleon III. Italian armies, led by General Alfonso Ferrero La Marmora, were to engage the Austrians on the southern front, while the Italians also planned to threaten the Dalmatian coast and seize Trieste. However, the Italian military was hampered by several factors, including the amalgamation of the armies of the Kingdom of Sardinia and the Kingdom of the Two Sicilies, which led to disputes among the chain of command.

On June 16, 1866, Prussia opened hostilities by attacking several German states allied with Austria. Three days later, Italy declared war on Austria and started military operations on June 23. The Italian forces were divided into two armies. One, under La Marmora himself, was deployed in Lombardy, west of the Mincio River, and the second, under Enrico Cialdini, was deployed in Romagna, south of the Po River. La Marmora was defeated at the Battle of Custoza on June 24 and retreated back across the Mincio River.

Following the defeat at Custoza, the Italians reorganised in preparation for an Austrian counter-offensive. The Austrians took the opportunity to raid Valtellina and Val Camonica. However, the course of the war turned in Italy's favour due to Prussian victories in Bohemia, particularly the Battle of Königgrätz on July 3. The Austrians were compelled to redeploy one of their three army corps from Italy to Vienna.

On July 14, during a council of war held in Ferrara, new Italian war plans were decided. Cialdini was to lead the main army of 150,000 troops through Venetia, while La Marmora, with roughly 70,000 men, would tie down Austrian forces. On July 26, a mixed Italian force defeated an Austrian force guarding the crossing of the Torre River and reached Romans d'Isonzo at the Battle of Versa. That marked the maximum Italian advance into Friuli.

In July 1866, after the Prussian victory over Austria, the Armistice of Nikolsburg ended hostilities between the two countries, with Italy obtaining Venetia. The Austrians withdrew to the Isonzo River and left Venice to Italian hands. The Treaty of Vienna, signed on October 3, 1866, confirmed the cession of the territory to Italy, with the annexation becoming effective after a plebiscite. The plebiscite was held on October 21 and 22, with an overwhelming majority (99.9%) supporting joining Italy.

The Treaty of Vienna

The provisions of the Treaty of Vienna included the surrender of the land of the former Venetian Republic (present-day Veneto and Friuli) and Mantua by Austria. Italian diplomats also attempted to obtain Trentino, but this was unsuccessful as the Austrians adhered to the text of the Armistice of Cormons, which established the former Kingdom of Lombardy-Venetia as the border. Emperor Franz Joseph had already agreed to cede Venetia and Mantua to France in exchange for non-intervention in the Austro-Prussian War. However, France, acting as an intermediary between Prussia and Austria, ceded them to Italy on 19 October, as agreed in a secret treaty in exchange for the earlier Italian acquiescence to the French annexation of Savoy and Nice.

The treaty also required Italy to pay a cash indemnity for each Austrian fort in Venetia and assume the state debt Venetia had accumulated under Austrian control. Additionally, Austria was made to give Italy the Iron Crown of Lombardy, the crown used by the medieval Kings of Lombardy. The annexation of Venetia and Mantua was made effective only after a plebiscite, which was held on 21 and 22 October 1866, with an overwhelming majority in support of joining Italy.

The Austro-Prussian War

Prussia had also formed an alliance with the Kingdom of Italy, which wanted Austrian-held territories to further the process of Italian unification. This diverted some Austrian forces to the south. Prussia's military advantages, such as better training and discipline, and a more extensive railway system, also contributed to their victory.

The war ended with the Treaty of Prague, which excluded Austria from German affairs and led to the formation of the North German Confederation, excluding Austria and the other southern German states. The treaty also resulted in the Italian annexation of the Austrian province of Venetia.

The Prelude to War

In the mid-19th century, Central Europe was divided into a few large and medium-sized states and hundreds of tiny entities, mostly within the Holy Roman Empire, ruled by the Holy Roman Emperor. Over time, the Empire shrank, and by 1789, it primarily consisted of German-speaking peoples. The Habsburg family, who ruled Austria, controlled the Emperorship from 1440 to 1806, but this role became increasingly ceremonial. After 1815, the German states were reorganized into the German Confederation, under Austrian leadership.

Prussia had been challenging Austrian supremacy since at least 1850, and by the mid-19th century, it had become one of Europe's great powers. Prussia's Minister President, Otto von Bismarck, played a key role in the conflict. He formed an alliance with Italy, committing it to the war if Prussia entered into one with Austria within three months. This incentivized Bismarck to go to war with Austria within that timeframe. Austria responded by mobilizing its Southern Army on the Italian border.

The War

On June 15, 1866, Bismarck offered territorial compensation in the Grand Duchy of Hesse to the Electorate of Hesse if Elector Frederick William allied with Prussia. However, this proposition offended Frederick William's sensibilities, and he joined the Austrians. Meanwhile, King George V of Hanover concluded that his kingdom would fall if it fought against Prussia and took some time to join the Austrian coalition. Most of the southern German states, including Bavaria and Württemberg, sided with Austria, while most northern German states, such as Oldenburg and Mecklenburg-Schwerin, joined Prussia.

The main campaign of the war took place in Bohemia. The Prussian army, led by King William I, rapidly mobilized and advanced across the border into Saxony and Bohemia. The Austrian army, led by Ludwig von Benedek, was concentrating for an invasion of Silesia. The two sides met at the Battle of Königgrätz on July 3, resulting in a decisive Prussian victory. An armistice between Prussia and Austria came into effect on July 22.

The Aftermath

The Peace of Prague on August 23, 1866, resulted in the dissolution of the German Confederation and the Prussian annexation of four of Austria's former allies. Austria was now excluded from German affairs, and Prussia was free to form the North German Confederation. The war left Prussia dominant in German politics and facilitated Italian unification.

The Italian War of Independence

The Third Italian War of Independence, also known as the Third War of Italian Unification, was fought between the Kingdom of Italy and the Austrian Empire from June to August 1866. This conflict ran parallel to the Austro-Prussian War, which saw Prussia vying for dominance over the German states. The Italian campaign against Austria was aided by an alliance with Prussia, which had committed to the war effort through a military alliance brokered by French Emperor Napoleon III.

The Italian campaign aimed to capture the region of Venetia, which included the territories of present-day Veneto, Friuli, and the city of Mantua. Venetia was a wealthy and populous region and held strategic importance for Italy. The Italian forces were divided into two armies, one led by General Alfonso Ferrero La Marmora and the other by Enrico Cialdini. However, the Italian military faced several challenges, including the amalgamation of formerly rival armies, resentment in Southern Italy due to recent annexations, and rivalry between the navies that formed the unified Italian navy.

The war began with Prussia's attack on several German states allied with Austria on June 16, 1866, followed by Italy's declaration of war on Austria three days later. The Italian armies advanced, with La Marmora's forces moving towards the powerful Austrian fortress in the Quadrilatero region, and Cialdini's army aiming for Mantua and Rovigo. However, La Marmora suffered a defeat at the Battle of Custoza on June 24 and retreated. Cialdini conducted shows of force but did not engage offensively in the early part of the war.

The tide turned in Italy's favour due to Prussian victories in Bohemia, particularly the Battle of Königgrätz on July 3, which compelled the Austrians to redeploy their forces. On July 14, new Italian war plans were decided, with Cialdini leading the main army through Venetia, and Garibaldi's volunteers advancing towards Trentino. However, the Italian Navy suffered an unexpected defeat at the Battle of Lissa on July 20.

The Armistice of Nikolsburg, which ended hostilities between Prussia and Austria, also resulted in Austria conceding Venetia to Italy. The Armistice of Cormons, signed on August 12, formalised the cessation of hostilities, and the Treaty of Vienna on October 3, 1866, confirmed the cession of Venetia to Italy. A plebiscite was held on October 21 and 22, with an overwhelming majority supporting the annexation of Venetia to the Kingdom of Italy.

The Italian Unification

The main obstacle to Italian Unification was the Habsburg monarchy, which directly or indirectly controlled much of Italy and was actively invested in keeping Italy divided. To overcome Austrian military power, Piedmont (then Italy from 1861) relied on foreign intervention by other European nations. The Piedmontese Prime Minister, Camillo Benso, formed an alliance with France, agreeing to turn over the French-speaking province of Savoy and Nice in exchange for military support against Austria. This support was vital to Italian success in the Second War of Italian Unification, which resulted in the Austrians ceding Lombardy to Piedmont.

In 1866, Italy took advantage of the conflict between Austria and Prussia over the administration of Schleswig and Holstein and the future of the German Confederation. Italy sided with Prussia in the conflict, declaring war on Austria in June 1866. This conflict is known as the Third Italian War of Independence. Italian armies, led by General Alfonso Ferrero La Marmora, engaged the Austrians in the south, while also planning to threaten the Dalmatian coast and seize Trieste. However, the Italian military was hampered by several factors, including the amalgamation of the armies of the Kingdom of Sardinia and the Kingdom of the Two Sicilies, as well as resentment and resistance in Southern Italy following the annexation of the Kingdom of the Two Sicilies.

Despite initial defeats at the Battle of Custoza and the Italian Navy's defeat at the Battle of Lissa, Italy was eventually able to gain the upper hand due to Prussian victories over Austria, particularly the Battle of Königgrätz in Bohemia. This compelled the Austrians to redeploy their forces to Vienna, leaving them vulnerable in the Italian theatre. The Armistice of Nikolsburg ended hostilities between Austria and Prussia, with Italy obtaining Venetia. The Treaty of Vienna, signed on 3 October 1866, confirmed the terms of the armistice, resulting in the transfer of Venetia and most of Friuli to the French Empire, who then gave the region to Italy after a referendum.

The acquisition of Venetia represented a major step in the Unification of Italy. However, Italy's poor performance in the war allowed Austria to retain several strategic mountain passes and peaks in the Alps, which would have serious strategic implications for Italy during the First World War. The Treaty of Vienna brought greater prestige to the Italian state and elevated its diplomatic position in Europe as a great power. However, Italian nationalists, including Garibaldi, felt that Italy had not gained enough territory, fuelling Italian irredentism in the late 19th century.

Frequently asked questions