Giangaleazzo was a feared and hated tyrant of Milan from 1386 to 1406. He had inherited the streak of insanity and cruelty that runs through many of the Dukes of Milan. He was not the immediate heir to the throne, but he overthrew his uncle Bernabo through treacherous means in 1385 to gain control of the Duchy and proceeded to rule it with an iron fist. The Duke developed new and innovative statecraft techniques including the Lenten treatment, forty days of slow but continuous torture. He was also fond of having prisoners devoured by dogs.
The cruel and ambitious Giangaleazzo was also a skilled statesman. Soon after seizing Milan he took Verona, Vicenza, and Pavia and soon controlled almost the entire Po river valley. He used the bounty of these conquests to buy the title of Duke from the Holy Roman Emperor for the price of 100 000 Florins. Giangaleazzo had dreams of uniting all of northern Italy into one empire, and many of the people of Italy supported this ambition. The many obstacles to his success were Bologna and especially Florence. In 1394 Giangaleazzo launched assaults upon these cities. The warfare was extremely taxing on both sides, but it was universally believed the Milanese would emerge victorious. In 1395 Bologna fell and the final siege of Florence began. The Florentine leaders, especially Coluccio Salutati worked successfully to rally the people of Florence, but the Florentines were being taxed hard by famine, disease, and poverty.
Giangaleazzo's dreams were to come to naught, however, as he succumbed to a fever in 1406. The siege of Florence was lifted and soon his entire empire crumbled as infighting among his successors racked Milan.