The Second Italian War or Italian War of Louis XII (1499-1503) began with the French conquest of Milan, which was followed by a joint Franco-Spanish campaign in Naples, and ended with a war between the former allies that began the long period of Spanish rule in Naples (Italian Wars, 1494-1559).
The French kings had inherited the Angevin claim to Naples, which by the late fifteenth century was ruled by a branch of the royal family of Aragon. In 1494 Charles VIII had launched an invasion of Naples (First Italian War/ Italian War of Charles VIII). He successfully conquered the kingdom, but his quick success triggered an anti-French alliance. Charles was forced to leave Naples and was able to fight his way back into northern Italy before returning to France. The troops he left in Naples were soon overwhelmed, and the status-quo in Italy appeared to have been largely restored.
In 1498 Charles died and Louis XII came to the throne. He also inherited the claim to Naples, and also added a claim to Milan. During the first war Ludovico Sforza duke of Milan, switched sides, going from being an ally of Charles VIII in 1494 to a member of an anti-French alliance in 1495. Louis had ended up fighting the Milanese in 1494 (as Louis of Orleans), and had argued in favour of a prolonged campaign against Milan late in 1495.
Phase One - Milan
When Louis of Orleans inherited the throne as Louis XII he was in a position to enforce his claim to Milan. He was crowned as Duke of Milan and King of Sicily as well as King of France, and then spent a year preparing for his new campaign. In July 1498 he made a treaty with Ferdinand and Isabella of Spain. He became involved in prolonged negotiations with Philip, Archduke of Austria, the son of the Emperor Maximilian and father of the future Charles V, securing his neutrality in the upcoming war. In March 1499 he signed a treaty with the Swiss cantons in which they agreed to provide troops at an agreed rate of pay and in return he agreed to pay then 20,000 florins a year and provide assistance in any Swiss wars. In February 1499 Venice agreed to partition Milan with the French - Venice would take Cremona and the area east of the Adda and in return provide cash to help fund the campaign. Pope Alexander VI was won over with a good marriage for his son Cesare Borgia. Florence provided secret support for the invasion.
In contrast Ludovico struggled to find allies. His most important friend was the Emperor Maximilian, but he was unable to offer any concrete help in 1499 and was distracted by a war with the Swiss. He did manage to hire a few mercenaries. Naples promised to send troops, but they never arrived. The fortress of Alessandria was reinforced.
Louis sent 17,000 infantry (including 6,000 Swiss) and 9,000 cavalry, supported by an impressive artillery park across the Alps. By 10 August the army, commanded by the Milanese exile Gian Giacomo Trivulzio was at Asti. Annone, Valenza and Tortona fell quickly, and the French arrived outside the strong fortress of Alessandria on 25 August. The commander fled four days later and the strong fortress fell on 29 August (siege of Alessandria).
This triggered trouble in the streets of Milan. Ludovico's treasurer was killed in the streets on 30 August, and on 2 September Ludovico fled from the city. He left a garrison in the Castle of Milan, but the commander surrendered the castle in return for 150,000 ducats. The allies split the Duchy as agreed, with Venice occupying the area east of the Adda and France the area to the west. Parma and Piacenza also quickly accepted French rule. Louis himself made his formal entry into Milan on 6 October, spent one month in the city and then returned to France, leaving Trivulzio in command.
The French weren't left in possession of Milan for long. Ludovico managed to arrange a truce between Maximilian and the Swiss, agreed on 22 September, and then raised an army of 20,000 men, including 1,500 men at arms from Burgundy and a sizable Swiss contingent. In January 1500 Ludovico launched a two-pronged invasion. He advanced from Bormio and then down Lake Como, while the Swiss invaded from the west via Aosta. The French attempted to stop Ludovico at Como but were forced to retreat on Milan. On 3 February Trivulzio left Milan, leaving a garrison in the castle and the French retreated west to Novara and Mortara. Ludovico entered Milan in triumph of 5 February.
Ludovico was now forced to split his army. Reinforcements under Yves d'Allègre had reached the French at Novara and Mortara on 13 February, and they also held the Castle of Milan. While part of his army besieged the castle, Ludovico moved south to Pavia then west to Vigevano (south-east of Novara, north-east of Mortara), which fell after a short siege. He then began a siege of Novara (5-21 March 1500), which ended with the surrender of the French garrison.
This was Ludovico's last success. French reinforcements arrived at Mortara on 23 March, bringing with them a new commander, Louis de la Tremouille. A body of Swiss joined on 3 April, making the two armies about equal. The French were well funded and morale was greatly improved by the replacement of Trivulzio, while in Ludovico's camp pay was running short and it wasn't clear if his Swiss troops would fight the French Swiss. On 8 April the French attacked, and Ludovico's army dissolved (battle of Novara, 8 April 1500). Ludovico attempted to escape amongst the Swiss, but was captured on 10 April.
The French were now the dominant power in northern Italy, ruling Milan, and allied with Florence, Venice and the Papal States. They were willing to support their allies with force - French troops helped Cesare Borgia in his campaigns in the Papal States, and in June-July they carried out an unsuccessful siege of Pisa on behalf of Florence.
Phase Two - Naples
The conquest of Milan was only the first part of Louis's plans for Italy. On 11 November 1500, in the Treaty of Granada, he and Ferdinand II of Aragon had agreed to split Naples between them, using the threat of an Ottoman takeover as their excuse (even though Ferdinand of Aragon had helped restore his relative Ferdinand II of Naples in the First Italian War).
Naples quickly fell to the temporary allies. The French left Lombardy in May. In June the Pope issued a bull depriving King Frederick IV of his kingdom. In July the French captured Capua, and at the start of August Frederick abandoned Naples. Taranto held out for some time, but eventually fell when Gonsalvo de Cordoba moved a fleet across land to a lake behind the city (March 1502).
The allies very quickly fell out. Several parts of Naples weren't covered by the Treaty of Granada, and the dispute broke out into open warfare in July 1502. Cordoba, who only had 4,000 men, was faced with a much larger French force of around 10,000 men under Louis d'Armagnac, Duke of Nemours. Cordoba was forced to retreat into the port of Barletta in Apulia, where he was loosely besieged from August 1502 until April 1503.
In April 1503 6,000 Spanish reinforcements reached Cordoba by sea. He decided to go onto the offensive, and advanced to Cerignola. On 26 April the French attacked his new position, but their attack was repulsed by the Spanish infantry. The Spanish then counterattacked and defeated the French. Nemours was killed in the battle, and the French position in Naples began to unravel (battle of Cerignola). A few days earlier a second French army, commanded by Bernard Stuart, Seigneur of Aubigny, had been defeated at Seminara (21 April 1503). Naples fell on 13 May. The castle of Uovo, near Naples, was taken after the engineer Navarro detonated a spectacular mine on 26 June, and Cordoba advanced to besiege the fortress at Gaeta (June-October 1503).
The French and their Italian allies responded by sending a fresh army south, and in October Cordoba was forced to lift the siege of Gaeta and move to a stronger position on the Garigliano River. The French and their Italian allies then suffered from a crisis of command - the French commander, Louis de la Trémoille was ill, and his Italian colleagues didn't have the respect of the French, so were unable to attack while Cordoba was vulnerable.
The French cause wasn't helped by their split efforts - in August 1503 they began a series of probes in the Pyrenees, but these were defeated and came to an end in December. In the same month the French position in Naples collapsed.
In December 1503 Cordoba received reinforcements and decided to go onto the attack. He unexpectedly crossed the river and outflanked the allies (battle of the Garigliano, 28-29 December 1503). The French and Italian forces broke and fled into Gaeta, but their morale was broken and on 1 January 1504 they surrendered on generous terms. The French were allowed to return home by sea.
In 1505 Louis XII and Ferdinand agreed the Treaty of Blois. Louis abandoned his claims to Naples and acknowledged Spanish rule there. This began a long period of association between Naples and Spain, first under the Hapsburgs and under the Spanish Bourbons from the 1730s. The French continued to threaten Naples during the Italian Wars, but without any great success. When the fighting in Italy was renewed in 1508 (War of the League of Cambrai) most of the action was in the north and central Italy.