War of the Sicilian Vespers in the context of "Battle of the Gulf of Naples"

The Kingdom of Naples, officially the Kingdom of Sicily, was a state that ruled the part of the Italian Peninsula south of the Papal States between 1282 and 1816. It was established by the War of the Sicilian Vespers (1282–1302). Until then, the island of Sicily and southern Italy had constituted the "Kingdom of Sicily". When the island of Sicily revolted and was conquered by the Crown of Aragon, it become a separate kingdom also called the Kingdom of Sicily. This left the Neapolitan mainland in the possession of Charles of Anjou who continued to use the name "Kingdom of Sicily". Later, two competing lines of the Angevin family competed for the Kingdom of Naples in the late 14th century, which resulted in the murder of Joanna I at the hands of her successor, Charles III of Naples. Charles' daughter Joanna II adopted King Alfonso V of Aragon as heir, who would then unite Naples into his Aragonese dominions in 1442.

As part of the Italian Wars, France briefly ruled the territory in 1494 and at the beginning of the 16th century; it then went to war with Spain over the kingdom in 1502, a conflict that ended in a victory for Ferdinand II, who was in full control of the kingdom by 1504. The Spanish held control of Naples throughout the 17th century where it remained an important source of economic and military power for the Spanish Crown. 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. However, Naples and Sicily were conquered by Charles, Duke of Parma (of the Spanish Bourbons) during the War of the Polish Succession in 1734, he was then installed as King of Naples and Sicily from 1735. In 1816, Naples formally unified with the island of Sicily to form the Kingdom of the Two Sicilies.

The Capetian House of Anjou, or House of Anjou-Sicily was a royal house and cadet branch of the Capetian dynasty. It is one of three separate royal houses referred to as Angevin, meaning "from Anjou" in France. Founded by Charles I of Anjou, the youngest son of Louis VIII of France, the Capetian king first ruled the Kingdom of Sicily during the 13th century. The War of the Sicilian Vespers later forced him out of the island of Sicily, leaving him with the southern half of the Italian Peninsula, known as the Kingdom of Naples. The house and its various branches would go on to influence much of the history of Southern and Central Europe during the Middle Ages until it became extinct in 1435.

Historically, the house ruled the Counties of Anjou, Maine, Touraine, Provence and Forcalquier; the Principalities of Achaea and Taranto; and the Kingdoms of Sicily, Naples, Hungary, Croatia, Albania and Poland.

The Sicilian Vespers (Italian: Vespri siciliani; Sicilian: Vespiri siciliani) was a successful rebellion on the island of Sicily that broke out at Easter 1282 against the rule of the French-born king Charles I of Anjou. Since taking control of the Kingdom of Sicily in 1266, the Angevin government had made itself unpopular with its exploitative policies and exclusion of native Sicilians from power.

Sparked by an incident in Palermo, the revolt quickly spread to the majority of Sicily. Within six weeks, approximately 13,000 French men and women were slain or expelled by the rebels, and the government of Charles lost control of the island. Seeking support for the rebellion, the Sicilians offered the throne to Peter III of Aragon, who claimed the crown on behalf of his wife, Constance of Sicily. The Aragonese intervention in the rebellion led to an expansion of the conflict into the War of the Sicilian Vespers.

The history of Sicily has been influenced by numerous ethnic groups. It has seen Sicily controlled by powers, including Carthaginian, Greek, Roman, Vandal and Ostrogoth, Byzantine, Arab, Norman, Aragonese, Spanish, Austrians, but also experiencing important periods of independence, as under the indigenous Sicanians, Elymians, Sicels, the Greek-Siceliotes (in particular Syracuse with its sovereigns), and later as County of Sicily, and Kingdom of Sicily. The Kingdom was founded in 1130 by Roger II, belonging to the Siculo-Norman family of Hauteville. During this period, Sicily was prosperous and politically powerful, becoming one of the wealthiest states in all of Europe. As a result of the dynastic succession, the Kingdom passed into the hands of the Hohenstaufen. At the end of the 13th century, with the War of the Sicilian Vespers between the crowns of Anjou and Aragon, the island passed to the latter. In the following centuries the Kingdom entered into the personal union with the Spaniard and Bourbon crowns, while preserving effective independence until 1816. Sicily was merged with the Kingdom of Italy in 1861.Although today an Autonomous Region, with special statute, of the Republic of Italy, it has its own distinct culture.

Sicily is both the largest region of the modern state of Italy and the largest island in the Mediterranean Sea. Its central location and natural resources ensured that it has been considered a crucial strategic location due in large part to its importance for Mediterranean trade routes. Cicero and al-Idrisi described respectively Syracuse and Palermo as the greatest and most beautiful cities of the Hellenic World and of the Middle Ages.

The Kingdom of Trinacria was established after Sicilian Vespers in 1282, when King Peter III of Aragon ascended the throne, and was consolidated after the War of the Sicilian Vespers in 1302. According to the Peace of Caltabellota, the Kingdom of Sicily was officially divided into two parts, one of which was the island part of Sicily, officially called the Kingdom of Trinacria, but informally called the Kingdom of Sicily.

Since then, Sicily island was ruled as an independent kingdom by relatives of the House of Barcelona, and was then added permanently to the Crown of Aragon as a result of the Compromise of Caspe of 1412. Meanwhile, the continental part of the Kingdom of Sicily, known colloquially as the Kingdom of Naples, remained under the crown of King Charles II of Anjou. The two resulting kingdoms were separated until 1442, when King Alfonso V of Aragon conquered the Kingdom of Naples and unified both Kingdoms.

Philip III (1 May 1245 – 5 October 1285), called the Bold (French: le Hardi), was King of France from 1270 until his death in 1285. His father, Louis IX, died in Tunis during the Eighth Crusade. Philip, who was accompanying him, returned to France and was anointed king at Reims in 1271.

Philip inherited numerous territorial lands during his reign, the most notable being the County of Toulouse, which was annexed to the royal domain in 1271. With the Treaty of Orléans, he expanded French influence into the Kingdom of Navarre and following the death of his brother Peter during the war of the Sicilian Vespers, the County of Alençon was returned to the crown lands.

The Aragonese Crusade (1284–1285), also known as the Crusade of Aragon or Crusade against Catalonia, was a military venture waged by the Kingdom of France against the Crown of Aragon. Fought as an extension of the War of the Sicilian Vespers (1282–1302), the crusade was called by Pope Martin IV in retribution for Peter III of Aragon's intervention in Sicily, which had damaged the political ambitions of the papacy and France.

The Kingdom of France, aided by the Kingdom of Majorca, led the crusade. Despite domestic opposition to the crusade, Philip III of France invaded Catalonia in 1285. While the French saw some successes on land, the Aragonese navy won control of the sea, and a badly attritted French crusader army was forced to retreat in the fall of 1285. The defeat of the French army in 1285 effectively ended fighting, and Aragon would make peace with the pope by way of the 1291 Treaty of Tarascon.