Cosimo I de' Medici: The Life and Legacy of Renaissance Florence's Most Powerful Ruler

Inevitably, given the time and place, the Medici's power in Florence was frequently threatened, and over the course of several turbulent decades, the family went through a sequence of exiles and restorations, until things finally reached a breaking point in January 1537. That month, Duke Alessandro de' Medici, the first member of the dynasty to control Florence as an open lord rather than a de facto ruler, had been killed by his cousin Lorenzino, who fled the city the same night and left no clear heir behind him. Many of the leading men of Florence, who had suffered through one Medici duke and despised him, looked about for someone they might raise in his place and, this time, govern on behalf of by making him a puppet.

They settled on 17-year-old Cosimo de' Medici, and, to be fair, almost nothing about him suggested he would become the powerful ruler he did. He had grown up far from the city, in the hill country where his branch of the family had its roots, as the son of a famous soldier and a devout mother. He had no training in statecraft and no faction of his own, which is precisely why the men who chose him chose him did so. As a Medici by blood who might lend their arrangements legitimacy while they kept the substance of power in their own hands, he seemed to be a harmless choice.

It was the gravest misjudgment of their careers and a seminal moment in the history of Italy, because in the span of months, the boy shattered an army of exiles in the field, sent the leaders of the old republic to the block, and began the slow, merciless work of making himself sole master of Florence. Within 20 years, he had conquered the rival republic of Siena and ruled nearly all of Tuscany, and in time, he had won from the pope a crown and a title no Florentine had ever carried as the Grand Duke of Tuscany. From that position of power, he established a royal dynasty that controlled Tuscany for two centuries.