She rode out of Cremona in May 1448 in parade armour, with Venetian troops pressing the city and Francesco Sforza away at Pavia. Chroniclers say Bianca Maria Visconti spent the day urging soldiers and townspeople to the walls. In that moment, the duke's wife looked less like a bride and more like a commander.

She had been born in 1425 near Settimo Pavese, the illegitimate daughter of Filippo Maria Visconti, Duke of Milan, and Agnese del Maino. Sent as a baby to Abbiategrasso, she grew up in comfort, with a humanist education, a great ducal library, and her father's taste for horses and the hunt. That mixture of learning and iron will stayed with her.

In 1430, when she was five, Filippo bound her to Francesco Sforza, a condottiero, a hired military captain, twenty-four years older. The match was politics in silk gloves: Milan needed Sforza tied close. After years of broken promises and shifting alliances, they finally married in 1441 at the Abbey of San Sigismondo in Cremona.

Marriage did not mean a quiet court. Bianca followed her husband through Venice, Rimini and Jesi as war moved around them, and in 1442 she was made regent of the Marche while he campaigned. The letters and chronicles show the pattern early: he strayed, she governed. When one mistress vanished in 1443, the warning was plain.

Then came the hinge. Filippo Maria died in 1447, Milan lurched into the Ambrosian Republic, and Venice threatened from outside. Bianca urged caution when Sforza was offered command, but he took it, fought for three hard years, and with her Visconti name helping win money and support, entered Milan in 1450 as duke. Husband and wife rode to the Duomo on horseback, refusing the triumphal wagon.

As Duchess of Milan, Bianca was not ornamental. During the war with Venice she ran government from Milan, and after the Peace of Lodi in 1454 she turned to building and repair: the Ospedale Maggiore, churches, the ducal residences. In 1459 she backed Pope Pius the Second's Mantua council with three hundred knights. When Francesco fell ill in 1462, she again held the duchy together against rebellions stirred by Venice.

The cost came from inside her own house. Francesco died in 1466, and Bianca ruled briefly until her eldest son, Galeazzo Maria Sforza, returned from France. He soon pushed her aside and forced her from Milan to Cremona. In 1468, after attending his wedding, she fell ill at Melegnano with a high fever and died on 28 October, asking that her younger children, Elisabetta and Ottaviano, be entrusted to their brother.

She was buried in the Duomo of Milan beside Francesco, with a funeral oration by Francesco Filelfo. Her son was accused by men including Bartolomeo Colleoni of poisoning her, though proof never came. What does remain clear is simpler: in the hardest years of Sforza Milan, Bianca Maria Visconti repeatedly acted as the steadier ruler.