The War of the Quadruple Alliance (1717-1720) was a result of the ambitions of Bourbon King Philip V of Spain, his wife, Elisabeth Farnese, and his chief minister Giulio Alberoni to retake territories in Italy lost to the Habsburgs in Vienna, and perhaps even to claim the French throne. It saw the defeat of Spain by an alliance of Britain, France, Austria (then a state of the Holy Roman Empire), and the Dutch Republic. Savoy later joined the coalition as the fifth ally. Although fighting began as early as 1717, war was not formally declared until December 1718. It was brought to an end by the Treaty of The Hague in 1720.
Charles II of Spain died in 1700 leaving no heirs to succeed him. By his will, he named Philip, Duke of Anjou, grandson of Louis XIV of France, as his successor. This led to the War of the Spanish Succession (1701-1714), at the end of which Philip, Duke of Anjou, was recognized as King Philip V of Spain, but on the condition that he be removed from the French line of succession, thereby ensuring that the French and Spanish crowns would never be united.
By the Treaty of Utrecht (1713), Spain lost all its possessions in Italy and the Low Countries. The Spanish Netherlands, Duchy of Milan, Naples and Sardinia were given to Emperor Charles VI of Austria, while Sicily was awarded to the Duke of Savoy and Prussia received the Spanish Guelders. These lands had been under Spanish Habsburg control for nearly two centuries, and their loss was perceived as a great blow to the country in both practical and prestige terms.
However, the first priority for Spain was the restoration of the country after 13 years of war, which had in part been fought on Spanish territory. The main architect of this operation was Giulio Alberoni. Alberoni was an Italian cardinal and steward of the archbishop of Piacenza. In 1714, Alberoni had arranged the marriage of the widowed Philip V to the 21-year-old Italian Elisabeth Farnese. In the process, Alberoni became the personal adviser of the new queen. In 1715, Alberoni became prime minister and reformed the country's finances. He also initiated the rebuilding of the Spanish fleet (with 50 ships of the line built in 1718 alone) and reformed the army. In 1717, Alberoni became a cardinal in the Roman Catholic Church. The Queen, who had several dynastic claims to advance in Italy, stimulated the Italian ambitions of her husband and their sons, supported by Alberoni.
In France, Louis XIV died in 1715 leaving only one infant great-grandchild, Louis XV, as his successor, while Philip V, the only surviving grandchild of Louis XIV, and his sons were excluded from succession to the crown of France by the Treaty of Utrecht.
Philip V nevertheless claimed the French throne in the event of the death of the infant Louis. Opposition to Philip's ambitions led France (where Louis XIV's nephew, the Duke of Orléans, served as regent), Great Britain, and the Dutch Republic, to join together in the Triple Alliance on 4 January 1717.
Great Britain, in particular, had become very concerned by Spanish ambitions in the Mediterranean Sea and Russian expansion in the Baltic and dispatched fleets to both as a preventative measure. The French navy was badly weakened from the recent war, and could not offer much support.
Later in the year, to strengthen the Treaty of Utrecht, Britain, France, and Austria contemplated ceding Sicily to Emperor Charles VI. This arrangement displeased Spain, which wanted to regain Sicily.
The initial Austrian reaction to this invasion was limited, as the Austrian Supreme Commander, Prince Eugene of Savoy, wanted to avoid a major war in Italy as long as the conflict in the Balkans continued, soaking up Austrian troops and resources. Finally, on 21 July 1718, the Treaty of Passarowitz ended the war with the Ottoman Empire. On 2 August, the Emperor joined the Triple Alliance, which became the Quadruple Alliance for which the war is named.
Meanwhile, in July 1718 the Spanish, this time with 30,000 men again led by the Marquis of Lede, had also invaded Sicily, which had been awarded to the Duke of Savoy. They took Palermo on 7 July and then divided their army in two. De Lede followed the coast to besiege Messina between 18 July and 30 September, while the Duke of Montemar conquered the rest of the island.
The French, Austrians, and British now demanded Spanish withdrawal from Sicily and Sardinia. The attitude of Victor Amadeus II of Savoy was ambiguous, as he agreed to negotiate with Cardinal Alberoni to form an anti-Austrian alliance.
On 2 August 1718, Britain, France and Austria joined with the United Provinces of the Netherlands to form the Quadruple Alliance in the Treaty of London.
On 11 August, at the Battle of Cape Passaro, a British fleet, led by Sir George Byng, effectively eliminated the Spanish fleet stationed off Sicily. This was followed in the autumn by the landing of a small Austrian army, assembled in Naples by the Austrian Viceroy Count Wirich Philipp von Daun, near Messina to lift the siege by the Spanish forces. The Austrians were defeated in the First Battle of Milazzo on 15 October, and only held a small bridgehead around Milazzo.
In 1718, Cardinal Alberoni began plotting to replace the Duc d'Orléans, regent to the 5-year old King Louis XV of France, with Philip V. This plot became known as the Cellamare Conspiracy. After the plot was discovered, Alberoni was expelled from France, which declared war on Spain. By 17 December 1718, the French, British, and Austrians had all officially entered the war against Spain. The Dutch would join them later, in August 1719.
The Duc d'Orléans ordered a French army under the Duke of Berwick to invade the western Basque districts of Spain in April 1719, still under the shock of Philip V's military intervention against them. The Duke of Berwick's army met very little resistance, but was forced back by heavy losses due to disease. A second attack in Catalonia suffered the same fate. In the Americas, the French were more successful and took Pensacola in Florida.
In Sicily, the Austrians started a new offensive under Count Claude Florimond de Mercy. They first suffered a defeat in the Battle of Francavilla (20 June 1719). But the Spanish were cut off from their homeland by the British fleet and it was just a matter of time before their resistance would crumble. Mercy was then victorious in the second Battle of Milazzo, took Messina in October and besieged Palermo.
It was also in 1719 that the Irish exile, the Duke of Ormonde, organized an expedition with extensive Spanish support to invade Britain and replace King George I with James Stuart, the Jacobite "Old Pretender". However, his fleet was dispersed by a storm near Galicia in 1719, and never reached Britain. A small force of 300 Spanish marines under George Keith, tenth Earl Marischal did land near Eilean Donan, but they and the highlanders who supported them were defeated at the Battle of Eilean Donan in May 1719 and the Battle of Glen Shiel a month later, and the hopes of an uprising soon fizzled out.
In retaliation for this attack, a British fleet captured Vigo and marched inland to Pontevedra in October 1719. This caused some shock to the Spanish authorities as they realized how vulnerable they were to Allied amphibious attacks, with the potential to open up a new front away from the French frontier.
The French captured the Spanish settlement of Pensacola in Florida in May 1719, pre-empting a Spanish attack on South Carolina. While Spanish forces retook the town in August 1719, it fell to the French again towards the end of the year and they destroyed the town before withdrawing.
Displeased with his kingdom's military performance, Philip dismissed Alberoni in December 1719, and made peace with the allies with the Treaty of The Hague on 17 February 1720.
In the treaty, Philip was forced to relinquish all territory captured in the war. However, his third surviving son's right to the Duchy of Parma and Piacenza after the death of Isabella's childless half-cousin, Antonio Farnese, was recognized.
France returned Pensacola and the remaining conquests in the north of Spain in exchange for commercial benefits. Included in the terms of this treaty, the Duke of Savoy was forced to exchange his throne in Sicily for that of the less important Kingdom of Sardinia.
The war provided a unique example during the eighteenth century when Britain and France were on the same side. It came during a period between 1716 and 1731 when the two countries were allies. Spain would later join with France in the Bourbon Compact, and the two would become enemies of the British once more.