Quadruple Alliance.
1. 1718. After the War of the Spanish Succession, Philip V of Spain was anxious to regain territory. France, Britain, and the Dutch formed a defensive Triple Alliance in 1717, which the Emperor Charles VI joined in 1718. The other allies agreed to support the Hanoverian succession in Britain. The emperor was to be given Sicily, and Sardinia was to go to Savoy. A British naval squadron defeated the Spanish fleet off Cape Passaro immediately after the treaty had been signed in 1718, and a French invasion of Spain in 1719 forced Philip to come to terms.

2. 1815. At the end of the Revolutionary and Napoleonic wars in 1815, the victorious powers—Britain, Russia, Prussia, and Austria—formed a Quadruple Alliance to maintain the peace and to hold periodic conferences to consider matters of common interest—the so-called Congress system. Meetings were held at Aix-la-Chapelle (1818), Troppau (1820–1), and Verona (1822), but differences between the allies were soon apparent. See Holy Alliance.

3. 1834. In the 1830s, the young queens of Portugal and of Spain were challenged by their uncles. Britain and France formed a Quadruple Alliance with Spain and Portugal in 1834 to protect them, as constitutional rulers, against intervention by Metternich. ‘All my own doing’ was Palmerston's claim, and he saw the alliance as a counter-balance to the despotic powers of Eastern Europe. But the alliance was short-lived and the liberalism of the queens suspect.

J. A. Cannon

Quadruple Alliance Coalition between four states, in particular three alliances in Europe in the 18th and 19th centuries. The first was formed (1718) by Britain, France, the Holy Roman Empire, and the Netherlands against Philip V of Spain, after he seized Sicily and Sardinia. The second was formed (1814) by Austria, Britain, Prussia, and Russia against Napoleon I of France. After Napoleon's defeat the four partners created the Congress system. The third Quadruple Alliance (1834) consisted of Britain and France in support of Portugal and Spain, where liberal monarchies were threatened by reactionary claimants.