How did Cosimo I turn Florence into an authoritarian state?

Cosimo I de' Medici established an authoritarian state in Florence primarily by consolidating personal control and rendering existing republican institutions powerless. After being elected head of the republic in 1537 following the assassination of his cousin Alessandro, Cosimo quickly moved to dismantle the traditional government structures, including the senate, the assembly, and the council.1

His rise to power was solidified through military and political maneuvers:
* Military Suppression: With the support of the Holy Roman Emperor Charles V, Cosimo defeated a band of exiles at the Battle of Montemurlo in 1537 and executed the principal captives, effectively silencing opposition.1
* Title and Legitimacy: He secured the emperor’s approval to style himself duke, transitioning from a republican official to an absolute ruler.1
* Territorial Expansion: Cosimo expanded his influence by conquering the republic of Siena in 1555, eventually becoming the first grand duke of Tuscany in 1569.1

By centralizing authority and bringing nearly all of Tuscany under his control, Cosimo transformed Florence from a republic into a despotic state, utilizing his power to oversee public services and promote his own dynastic interests.1