Sforza, returning to the siege of Piacenza and finding the city not likely to crumble by starvation, resolves to storm it.

Employing cannons in an almost unheard-of manner, he opens up a breach in the walls and sacks the city.

The news of this sack is greeted by three days' rejoicing in Milan.

Bartolomeo Colleoni, a Milanese captain, meanwhile captures Tortona, which had previously proclaimed Sforza as its lord, stealing it from the now dangerously powerful Sforza.

This causes further and even greater rejoicing, for the Milanese fear Sforza.

The Milanese force led by Sforza is the victor in the Battle of Caravaggio, fought near Caravaggio, in Lombardy (northern Italy), between the armies of the Ambrosian Republic and the Republic of Venice, on September 15, 1448.

Sforza has in the meantime also received the seigniory of other cities of the duchy, including Lodi, and starts to carefully plan the conquest of the ephemeral republic, allying with William, the third son of Marquess John Jacob of Montferrat.

Sforza, who has secretly negotiated with Venice during the entire campaign, now switches sides, renouncing his Milan connection and allying himself with Venice.

Refused entry by the Milanese in answer to his treachery, Sforza besieges the city.

The Ambrosian Republic capitulates in 1450; Sforza is granted entrance, and control of the city passes to its conqueror, who is declared duke.