War of the Quadruple Alliance

Everyone knows about the War of the Spanish Succession, the 1701-1714 conflict that ended with the Treaty of Utrecht, one of the most famous treaties of all time.

But did you know that there was a direct sequel? There was, and it's called the War of the Quadruple Alliance. It lasted from 1717 to 1720.

Under the Treaty of Utrecht, the House of Bourbon, under the new Spanish king Philip V, was allowed to keep Spain, but at the cost of giving up a lot of formerly territory, including wide swaths of Italy. The War of the Quadruple Alliance was an attempt by Philip V to regain this land.

The war was planned by Philip V's chief minister, Cardinal Alberoni. Under Alberoni's plan, Spain invaded and occupied Sardinia and Sicily.

Britain and France allied to oppose these invasions. Austria, whose interests in Italy were clearly threatened, did not immediately intervene due to being at war with the Ottoman Empire, but after ending that war in the 1718 Treaty of Passarowitz they joined the anti-Spanish alliance. The Netherlands also joined, forming the war's eponymous four-country coalition.

Cardinal Alberoni, knowing that four was greater than one, attempted to de-stabilize Spain's rivals using intrigue. Alberoni attempted to finance a new Jacobite rising in Britain (which had just recently been rocked by "The Fifteen", the appropriately-named Jacobite uprising of 1715), and Alberoni also supported the Cellamare Conspiracy, which attempted to assassinate the regent of France. (Louis XIV had died in 1715 and left a 5 year old son, so killing the regent would leave France without a capable ruler). Both of these failed.

Alberoni's military campaigns also failed. The allies destroyed the Spanish fleet at the Battle of Cape Passaro, defeated the Spanish on land at the Battle of Milazzo, and even temporarily captured the Spanish towns of Vigo (in Spain) and Pensacola (in Florida).

The war was ended by the Treaty of the Hague, which mostly returned Europe to the status quo ante. The most notable provision of the treaty was that Sicily was given to Austria. The House of Savoy, which had been given Sicily under the Treaty of Utrecht, was given Sardinia instead. From here, they would eventually unify Italy.

As for Cardinal Alberoni, he was expelled from Spain and banned from ever returning.