“Portrait as Trophy: Three Imperial Busts by Leone Leoni,” by Jonathan Marsden, Royal Collection, London

• Art/Photo

Around 1555 the Duke of Alba commissioned three life-sized bronze busts by the great Italian Renaissance portraitist Leone Leoni: one of himself and the other two of the Hapsburg emperor Charles V and the emperor’s son, Philip II of Spain. Though the busts depict sitters of different rank—an emperor, a king, and a duke—Leoni presents them almost identically, as armored warriors in the cause of the Counter Reformation. For more than a century they have adorned the Guard Chamber at Windsor Castle, surrounded by actual weaponry and armor. Just as victorious Romans piled up the armor of their enemies as offerings to the gods, so George IV (who acquired the busts in 1825) turned these symbols of power into trophies of war