Charles' daughter Joanna II adopted King Alfonso V of Aragon as heir, who would then unite Naples into his Aragonese dominions in 1442.

After the War of the Spanish Succession in the early 18th century, the possession of the kingdom again changed hands; the 1714 Treaty of Rastatt saw Naples given to Charles VI of the Austrian Habsburgs.

Its territory corresponded to the current Italian regions of Campania, Calabria, Apulia, Basilicata, Abruzzo, Molise, and also included some areas of today's southern and eastern Lazio.

In the late Middle Ages, it was common to distinguish the two Sicilies by noting its location relative to the rest of Italy and the Punta del Faro, i.e., the Strait of Messina.

The Normans established a kingdom that included southern mainland Italy and the island of Sicily, which was primarily ruled from Palermo.

At his death in 1458, the War of the Neapolitan Succession (1458–1462) erupted, after which the kingdom was again separated and Naples was inherited by Ferdinand I, Alfonso's illegitimate son.

However, disputes over ownership of key Neapolitan territories made the deal quickly fall through, and Aragon and France resumed their war over the kingdom in 1502.

The Spanish troops occupying Calabria and Apulia, led by Gonzalo Fernandez de Cordova, invaded and expelled all Frenchmen from the area.

The peace treaties that continued were never definitive, but they established at least that the title of King of Naples was reserved for Ferdinand's grandson, the future Charles V, Holy Roman Emperor.

While the soldiers of Naples were under the command of the Spanish viceroy, Neapolitan nobles enjoyed ascendancy in the assemblies and committees that financed and administered the army.

From 1612 to 1646, Neapolitan taxes tripled and the public debt quintupled, and 57 percent of the kingdom's revenue was devoted to interest payments.

[12] Due to this excessive taxation the people of Naples rose in revolt in 1647, forming the Neapolitan Republic with French assistance.

Both Naples and Sicily were conquered by a Spanish army during the War of the Polish Succession in 1734, and Charles, Duke of Parma, a younger son of King Philip V of Spain, the first member of the French House of Bourbon to rule in Spain, was installed as King of Naples and Sicily from 1735.

When Charles inherited the Spanish throne from his older half-brother in 1759, he left Naples and Sicily to his younger son, Ferdinand IV.

On 29 November 1798, he effectively started the War of the Second Coalition by briefly occupying Rome, but was expelled from it by French Revolutionary forces within the year and safely returned home.

In January 1799, the French armies installed a Parthenopaean Republic, but this proved short-lived, and a peasant counter-revolution inspired by the clergy allowed Ferdinand to return to his capital.

However, in 1801 Ferdinand was compelled to make important concessions to the French by the Treaty of Florence, which reinforced France's position as the dominant power in mainland Italy.

After Napoleon's defeat in 1814, Murat reached an agreement with Austria and was allowed to retain the throne of Naples, despite the lobbying efforts of Ferdinand and his supporters.

Realising the Austrians would soon attempt to remove him, Murat gave the Rimini Proclamation hoping to save his kingdom by allying himself with Italian nationalists.