The War of the League of Cambrai (1508-1510) was fought between Venice and an alliance that included the Emperor Maximilian, Pope Julius II, Louis XII of France and Ferdinand II of Aragon, and that despite never coordinating its attacks managed to conquer large parts of the Venetian mainland empire before falling apart (Italian Wars, 1494-1559).
At the end of the Second Italian War Louis XII had agreed two treaties at Blois. The first, in September 1504, was between Louis and the Emperor Maximilian. Maximilian agreed to invest Louis as Duke of Milan in return for cash, while Louis then allocated Milan, Genoa, Asti, the duchy of Burgundy, Macon and Auxerre to the dowry of his daughter, after her proposed marriage to the future Emperor Charles V (Maximilian's grandson). In the second, agreed in October 1505 between Louis and Ferdinand II of Aragon, Louis surrendered his claim to Naples by making it the dowry of his niece Germaine of Foix after she married Ferdinand (the marriage took place in March 1506).
The first of these treaties was nullified in 1506 when Louis decided, under great public pressure, to marry his daughter Claude to Francis of Angouléme, the heir presumptive to the French throne (the future Francis I). This ensured the permanent union of Brittany with the kingdom of France.
The same year saw Pope Julius II begin his campaign to restore control of the Papal States. Venice had taken Faenza and Rimini after the death of Pope Alexander VI (1503) and refused to return them to the pope. He was able to re-conquer Perugia, and with French help retake Bologna, overthrowing usurpers in both places.
In 1507 Louis traveled to Italy to subdue a revolt in Genoa, overwhelming the city in April. In June he met with Ferdinand at Savona. The two monarchs agreed to try and form a league with Pope Julius and the Emperor Maximilian, although at this stage their enemy wasn't stated.
In fact the target was Venice. All four powers had some reason to dislike the serene republic. Julius wanted the return of Faenza, Rimini and Ravenna. Ferdinand wanted Brindisi, Otranto and number of other ports in Apulia that Venice had seized in 1495 when the French were being expelled from the Kingdom of Naples (First Italian War). Louis had given Venice the eastern part of the Duchy of Milan during the Second Italian War, but now clearly wanted it back. Maximilian had claims in Padua, Verona and Friuli, and had been denied free passage for his army, officially to escort him to Rome to be crowned Holy Roman Emperor.
Maximilian was the first to make a move against Venice, attacking the Republic in February 1508. Maximilian had great prestige but little wealth, and few of his campaigns were especially effective. The war against Venice went badly for him - Venice took Görz and Trieste in the east and held on elsewhere. The Venetians defeated an Imperial army at the battle of Cadore (2 March 1508) and in June the two sides agreed a three year truce.
As was almost always the case in this period the truce didn't last very long. In December Maximilian's daughter Margaret met with Louis's chief advisor, the Cardinal of Rouen, at Cambrai. There they agreed an anti-Venice alliance - the League of Cambrai (10 December 1508). The Cardinal spoke for France and for the Pope, although Julius didn’t officially join the league until March 1509. Ferdinand of Aragon was included in the league, possibly as a result of the negotiations of 1507. The war was to start by 1 April 1509, with Maximilian joining in within forty days and England and Hungary also invited to join.
The war didn't start quite on schedule. Louis was the first to move, declaring war on 7 April. Pope Julius followed on 27 April. The first fighting came on the Adda frontier, where the French got the best of the early manoeuvring. The Venetian army was defeated at Agnadello (14 May 1509), the only major battle of the war.
In the aftermath of this defeat the Venetians withdrew from most of their outlying territories - the ports in Apulia, the Romagna, Bergamo, Brescia, Crema and Cermona, Verona, Vicenza and Padua. At the same time a new army was raised, and negotiations began with the Pope.
In June the Emperor Maximilian finally appeared on the scene, arriving at Trent. By now Venice had recovered from the shock of Agnadello, and reoccupied Padua. Maximilian, with a large army of his own and French support, besieged Padua (8 August- 2 October 1509). A series of attacks on Padua failed. Eventually Maximilian was forced to ask the mounted men-at-arms to take part in an infantry assault on the city. The French are said to have accepted, the Germans to have refused, and this caused Maximilian to lift the siege. In the aftermath of this failure Maximilian retreated back into the Tyrol. The French also pulled back to Milan, forcing the Pole to retreat. The Venetians were able to reoccupy Vicenza.
The League of Cambrai began to fall apart early in 1510. Pope Julius had been worried by the brutality of the besieging troops at Padua, and was now worried about the dangers of foreign domination in Italy. In February 1510 he agreed a treaty with Venice. The Republic had to make a number of ecclesiastical concessions, mainly to do with the limits of Papal power in Venice. They also surrendered their claims to the cities in the Romagna they had taken in 1503, and agreed to open the Adriatic to all Papal shipping.
This marked the effective end of the War of the League of Cambrai. Pope Julius had now decided to create a new Holy League, with the aim of expelling the French from Italy. At first he struggled to find allies - the Emperor Maximilian was still focused on his hostility to Venice. Ferdinand of Aragon was on relatively friendly terms with the French, and had achieved his main aims in the war with the complete occupation of Apulia. Eventually the Holy League would expand to include Spain and England, and the second part of the conflict that had opened in 1509 would become the War of the Holy League (1510-1514).