The death of Henry VI was followed by a general war throughout the empire, which gave fresh activity to the passions of the Italian nobles, and greater animosity to the opposing parties. The two factions in Germany had simultaneously raised to the empire the two chiefs of the houses of Guelf and Ghibelline. Philip I, duke of Swabia, and brother of Henry VI, had been named king of the Romans by the Ghibellines; and Otto IV, son of Henry the Lion, duke of Bavaria and Saxony, by the Guelfs. Their contest was prolonged to the 22nd of June, 1208, when Philip was assassinated by a private enemy. The Germans, wearied with eleven years of civil war, agreed to unite under the sceptre of his rival, Otto IV, whom they crowned anew. The following year he passed into Italy, to receive from the pope the golden crown of the empire. But though Otto was the legitimate heir of the Guelfs of Bavaria, so long chiefs of the opposition to the imperial prerogatives, yet now wearing himself the crown, he was desirous of possessing it with these disputed rights; every one was denied him, and all his actions controlled by the pope. There was soon a declared enmity between the emperor and the pontiff who, rather than consent to any agreement, or to abate any of his pretensions, raised against the Guelf emperor the heir of the Ghibelline house, the young Frederick II, grandson of Frederick I, hardly eighteen years of age, and till then reigning under the pope’s tutelage over the Two Sicilies only. Frederick, excited and seconded by the pope, boldly passed through Lombardy in 1212, and arrived at Aachen, where the German Ghibellines awaited, and crowned him king of the Romans and Germans. Otto IV in the meantime returned to Germany, and was acknowledged by Saxony. The civil war, carried on between the two chiefs of the empire, lasted till the 19th of May, 1218, when Otto died, without any attempt by either party to despoil his rival of his hereditary possessions. It was this civil war that caused the names of Guelf and Ghibelline to be exclusively substituted for those of party of the church and party of the empire. In fact, each noble family, and each city, seemed to consult only their hereditary affection, and not their political principles, in ranging themselves under either standard. The Guelfs placed themselves in opposition to the pope, to repel his Ghibelline candidate; and Milan, Piacenza, and Brescia braved even excommunication to resist him; while, on the contrary the Ghibellines of Pavia, Cremona, and of the marches armed themselves with zeal against an emperor of the Guelf blood.