In this portrait, Cosimo is represented in his younger years, commanding and proud; and to quote Giorgio Vasari, "clad with white armor and a hand over the helmet".
Bronzino's portrait captures Duke Cosimo I following a great diplomatic triumph.
Cosimo had, at long last, rid Florence of the Spanish garrisons that had been stationed there since the early 1530s, when Pope Clement VII (Giulio de' Medici) and Holy Roman Emperor Charles V agreed that Florence would become an Imperial duchy, governed by the Medici.
Charles V stationed the garrisons in Florence ostensibly to protect its first duke, Alessandro de Medici, from those who might rise up against him or otherwise do him harm.
Cosimo I however chaffed under the watch of the Spanish troops, and in 1543, in return for a monetary payment to Charles V, (the latter needed funds to fight Protestants in Northern Europe), the duke obtained the evacuation of the garrisons stationed in Florence.