Frederick II (1194-1250) was Holy Roman emperor from 1215 to 1250. His unsuccessful effort to establish a strong centralized Italian state brought him into a long and bitter conflict with the papacy and the Italian urban centers.

Born in lesi, Italy, Frederick II was the only son of Emperor Henry VI and of Constance of Sicily. His father died in 1197 and his mother, who served as regent for him, a year later. As the orphan king of Sicily, he was the ward of the great pope Innocent III, who ignored his education and training but kept his kingdom intact for him. Frederick grew up in Palermo, surrounded by factions who attempted to use him for their own ends and influenced by the Islamic and Greek culture that pervaded the dissolute Sicilian court.

At first Frederick was ignored in the empire of his father, where his able uncle Philip of Swabia...