Charles VIII of France (1470-98, reigned 1483-98) began the long series of French invasions of Italy (Italian Wars), paying a great cost for his temporary occupation of Naples.
Charles was the only son of Louis XI, and came to the throne in 1483 when aged only 13. The first part of his reign was thus dominated by a regency lead by his sister Anne and her husband Pierre de Bourbon, seigneur de Beaujeu. The main success of their rule was the 1491 marriage between Charles and Anne of Brittany, a marriage that finally united the French crown and the Duchy of Brittany, ending a long weakness (the Dukes of Brittany had often been allies of England during the Hundred Years War). This marriage was forced on Anne of Brittany after the French invaded her duchy and forced her to renounce a proposed marriage with Maximilian of Austria. Although Charles died before they had had any children, Anne then married Louis XII. The union between France and Burgundy was confirmed when Anne's daughter Claude married the future Francis I.
Charles had inherited the Angevin claim to the throne of Naples, long lost to the rulers of Aragon. At the start of the 1490s Sicily was held by Ferdinand II of Aragon while Naples was held by Ferdinand I, a legitimised son of Alfonso V of Aragon. Charles spent the first part of the 1490s securing his flanks ready for the invasion of Italy, and also received support from Ludovico de Sforza, Regent of Milan, who was hoping to take advantage of the confusion to make himself Duke of Milan.
Charles spent the first years after he came of age preparing for his invasion of Italy. In 1492 he agreed the Treaty of Etaples in which he paid Henry VII to abandon the English claim to Brittany. In the 1493 Treaty of Barcelona he gave Roussillon and Cerdagne to Aragon, giving Spain a foothold east of the Pyrenees. He also offered refuge to Guiliano della Rovere, a bitter rival of Pope Alexander VI and the future Pope Julius II.
In 1494 Ferdinand I of Naples died, and was succeeded by his unpopular son Alfonso II. Charles decided that this was the right moment to invade (First Italian War/ Italian War of Charles VIII). He crossed the Alps and then made a rapid advance down Italy. At Florence he deposed the Medici and restored the Republic. At Rome Pope Alexander VI was forced to let him pass unopposed, but didn't offer support for his claim to Naples. In February 1495 Charles entered Naples, and for a few months it looked as if he had achieved his aims.
Charles's rapid progress had greatly alarmed the other Italian powers, and they formed the League of Venice to oppose him. This included the Pope, the Emperor Maximilian, Ferdinand and Isabella of Spain, Venice, and even Milan, where Ludovico had become aware that the French probably wanted his duchy as well. In May Charles decided to leave Naples to return north, leaving half of his army behind. He was able to force his way past a League army at Fornovo in the Apennines (July 1495), but the situation in the north had turned against him, and by October 1495 he had come to terms with Milan and returned to France. July also saw Ferdinand II welcomed back into Naples and the last French strongholds fell in 1496.
Charles hadn't abandoned his ambitions in Italy, but in 1498 he hit his head on a low doorway and died. He was succeeded by his cousin Louis, duke of Orleans, who became Louis XII. The new king shared his Italian ambitions, and invaded Italy himself in 1499 (Second Italian War/ Italian War of Louis XII, 1499-1503). Charles's ambitions triggered over half of century of warfare in Italy, which didn't end until 1559, and saw much of Italy fall under foreign rule.