In 1232, Frederick II., in order that he might seem to fulfil his neglected duties as German Emperor, summoned a general Diet to meet at Ravenna, but it was prevented by the Lombard cities, as the Diet of Verona had been prevented six years before. Befriended by Venice, however, Frederick marched to Aquileia, and there met his son, king Henry, after a separation of twelve years. Their respective ages were thirty-seven and twenty-one: there was little personal sympathy or affection between them, and they only came together to quarrel. Frederick refused to sanction most of Henry's measures; he demanded, among other things, that the latter should rebuild the strongholds of the robber-knights of Hohenlohe, which had been razed to the ground. This seemed to Henry an outrage as well as a humiliation, and he returned home with rebellion in his heart. After proclaiming himself independent king, he entered into an alliance with the cities of Lombardy and even sought the aid of the Pope. [Sidenote: 1235. FREDERICK'S MARRIAGE AT WORMS.] Early in 1235, after an absence of fifteen years, Frederick II. returned to Germany. The revolt, which had seemed so threatening, fell to pieces at his approach. He was again master of the Empire, without striking a blow: Henry had no course but to surrender without conditions. He was deposed, imprisoned, and finally sent with his family to Southern Italy, where he died seven years afterwards. The same summer the Emperor, whose wife, Iolanthe, had died some years before, was married at Worms to Isabella, sister of king Henry III. of England. The ceremony was attended with festivals of Oriental splendor; the attendants of the new Empress were Saracens, and she was obliged to live after the manner of Eastern women. Immense numbers of the nobles and people flocked to Worms, and soon afterwards to Mayence, where a Diet was held. Here, for the first time, the decrees of the Diet were publicly read in the German language. Frederick also, as the head of the Waiblinger party, effected a reconciliation with Otto of Brunswick, the head of the Welfs, whereby the rivalry of a hundred years came to an end in Germany; but in Italy the struggle between the Ghibellines and the Guelphs was continued long after the Hohenstaufen line became extinct.