These designs alarmed Venice, which allied with Milan to counter the common threat posed by the Carrarese state, and for the first time adopted a policy of direct intervention in the affairs of its hinterland.

In spring 1405, the Carrarese position began to deteriorate rapidly: Niccolò III d'Este took Ferrara out of the war, while on 22 June 1505, Verona rebelled and surrendered to the Venetian army.

[7] Allied to the Este lords of Ferrara in the west,[8] he purchased Treviso from the Habsburgs, thereby threatening to cut Venice off from the trade routes leading over the Alps to Germany.

[1][10] Padua itself fell briefly under Visconti rule, but in June 1390, with the backing of Florence and the tacit support of Venice, Francesco II 'il Novello' recovered control of the city.

Up until that point, the Venetian Senate was deliberating sending troops to aid the Carrarese lordship against the Duke of Milan, who had recently triumphed in battle over his enemies at Casalecchio.

[10][11] Francesco Novello immediately exploited the weakened position of the Visconti regime, joining a Papal league against Milan and making contact with the anti-Milanese rebels in Brescia and Bergamo.

Encouraged by Florence and the local Guelph party, he captured Brescia on 21 August 1403, only to be forced to abandon the city to the advancing Visconti troops within a month.

Not even the unravelling of the anti-Visconti league of Italian lords following the withdrawal of the Pope and the King of Germany, Rupert, which effectively left him alone to face the might of Milan, gave him pause.

[11] In late 1403, the lord of Padua turned his sights on Verona and Vicenza, and secured the support of his son-in-law, Niccolò III d'Este, ruler of Ferrara.

[13] The prospect of such an expansion of Carrarese power alarmed Venice, whose policy up to this point had been one of maintaining the status quo by playing off the various local potentates against each other.

[13] Jacopo dal Verme placed his own mercenary companies at the Republic's disposal,[13] while Francesco I Gonzaga of Mantua was persuaded to enter Venetian service in exchange for Ostiglia and Peschiera.

Paduan chroniclers record that the Venetian force was the largest seen in Italy since the wars of Frederick Barbarossa against the Lombard League in the 12th century, and that the Republic spent the vast sum of 120,000 gold ducats per month for their upkeep.

[13] The exact numbers are impossible to ascertain, especially since the Venetian forces operated in separate groups in different directions: against Verona, against Padua, and in the Polesine (backed by a fleet of eight galleys) against the Ferrarese.

[16] Another Florentine attempt to mediate a peace failed in January, 1405[11] and in March, the constant menace posed by the Venetian fleet and troops to Ferrara forced Niccolò III d'Este to conclude a pact with Venice, renouncing his claims on the Polesine.

[11] In the end, by decree of the Council of Ten, the three remaining members of the Carrara family were judged to be too dangerous to be left alive: Francesco Novello was strangled on 17 January 1406, and his two sons followed a few days later.

Furthermore, they were suspected of plans to poison the city's water supply, and there was considerable outrage as their captured account books showed that they had bribed Venetian nobles to serve as spies.

The King of Hungary, Sigismund, also became Holy Roman Emperor in 1410, and denounced the Venetian mainland state as illegitimate, upholding the claims of the previous dynastic families, the Scaligers and Carrara, who had been Imperial vicars of their cities.

[23] The Republic prevailed in this conflict,[22] and by 1437 even Sigismund had to concede an Imperial vicariate to the Doge Francesco Foscari, thus legitimizing their control over the Veneto–albeit an exception was made for the old Scaliger cities of Verona and Vicenza.