Sforza was coming close to Milan itself in his conquests, and decided that since it was too powerful to be taken by force, he would surround it and starve the populace into surrender.
With the loss of the outer cities by conquest or defection, Milan experienced famine.
Gonzaga offered Crema to Sforza, hoping he would be tempted to take it himself and betray the Venetians.
But Sforza remained staunch, and instead offered Gonzaga the city of Tortona if he would abandon Crema.
This was accepted, and Crema, without support, quickly capitulated.

To the Milanese, Sforza's victory now seemed certain, but he found his Venetian allies beginning to have doubts about their Captain-General.
They decided that Milan run by Sforza would be far more dangerous and detrimental to their interests than if it were run by a weak Republic.
The last of the territory claimed by Venice, namely Crema, was now captured.
Venice went behind Sforza's back and signed a peace treaty with the Republic.
They conceded conquered land to the Republic in return for peace, and let Sforza keep only Pavia, Cremona, Piacenza, and a narrow strip of land.
They ordered him to accept the treaty or find Venice his enemy.
The Republic rejoiced, and the citizens were confident the war was over and their future was secured.
But Sforza could not accept the conditions of the treaty, and decided to persevere in the struggle.
He was already very powerful, and moreover was close to Milan.
The Milanese in their assurance of peace had nearly exhausted their resources to plant crops and return to the old way of life.
He was confident that Milan would quickly fall to him.
After reinforcing his peace with Savoy with the concession of a few unimportant castles, he defeated the Venetians under his rival Sigismondo Malatesta and continued the siege.

Sforza chose for his headquarters the Borromeo castle of Peschiera, south-east of the city.
Starvation and suffering were rampant in Milan, and the Venetians had sent an ambassador, Leonardo Venieri, to negotiate the city's surrender and help them defeat Sforza.
At last, Gaspare da Vimercate and several members of the Stampa family engineered a coup on 24 February 1450, which resulted in the murder of Venieri on the stairs of Palazzo Reale.
The next day the citizens met and Da Vimercate convinced the people to surrender to Sforza.
Sforza had made himself very popular for his generosity while fighting for Milan.
He had abstained from ravaging the countryside as was so common among commanders of his day, and after some debate the public was convinced.
The following day terms were offered to Sforza, who accepted them.
Sforza earned the city's devotion by distributing food to the starving people.
On 22 March 1450, he had himself declared capitano del popolo, and by right of his wife, the Duke of Milan.
He secured his popular support by letting many office-holders keep their positions and being very lenient in his reprisals.
The leaders were briefly imprisoned or relegated to their estates, but were generally pardoned soon after, even knighting some of his old enemies at his coronation.
Ghibellines were allowed to return in safety and were restored to favor.
Sforza was coming close to Milan itself in his conquests, and decided that since it was too powerful to be taken by force, he would surround it and starve the populace into surrender. With the loss of the outer cities by conquest or defection, Milan experienced famine. Gonzaga offered Crema to Sforza, hoping he would be tempted to take it himself and betray the Venetians. But Sforza remained staunch, and instead offered Gonzaga the city of Tortona if he would abandon Crema. This was accepted, and Crema, without support, quickly capitulated. 
To the Milanese, Sforza's victory now seemed certain, but he found his Venetian allies beginning to have doubts about their Captain-General. They decided that Milan run by Sforza would be far more dangerous and detrimental to their interests than if it were run by a weak Republic. The last of the territory claimed by Venice, namely Crema, was now captured. Venice went behind Sforza's back and signed a peace treaty with the Republic. They conceded conquered land to the Republic in return for peace, and let Sforza keep only Pavia, Cremona, Piacenza, and a narrow strip of land. They ordered him to accept the treaty or find Venice his enemy. The Republic rejoiced, and the citizens were confident the war was over and their future was secured. But Sforza could not accept the conditions of the treaty, and decided to persevere in the struggle. He was already very powerful, and moreover was close to Milan. The Milanese in their assurance of peace had nearly exhausted their resources to plant crops and return to the old way of life. He was confident that Milan would quickly fall to him. After reinforcing his peace with Savoy with the concession of a few unimportant castles, he defeated the Venetians under his rival Sigismondo Malatesta and continued the siege.
Sforza chose for his headquarters the Borromeo castle of Peschiera, south-east of the city. Starvation and suffering were rampant in Milan, and the Venetians had sent an ambassador, Leonardo Venieri, to negotiate the city's surrender and help them defeat Sforza. At last, Gaspare da Vimercate and several members of the Stampa family engineered a coup on 24 February 1450, which resulted in the murder of Venieri on the stairs of Palazzo Reale. The next day the citizens met and Da Vimercate convinced the people to surrender to Sforza. Sforza had made himself very popular for his generosity while fighting for Milan. He had abstained from ravaging the countryside as was so common among commanders of his day, and after some debate the public was convinced. The following day terms were offered to Sforza, who accepted them. Sforza earned the city's devotion by distributing food to the starving people. On 22 March 1450, he had himself declared capitano del popolo, and by right of his wife, the Duke of Milan. He secured his popular support by letting many office-holders keep their positions and being very lenient in his reprisals. The leaders were briefly imprisoned or relegated to their estates, but were generally pardoned soon after, even knighting some of his old enemies at his coronation. Ghibellines were allowed to return in safety and were restored to favor.
Golden Ambrosian Republic