This was the period when mortal war was being waged between Pope Gregory IX. and the Emperor Frederick II. The Emperor had been cursed and excommunicated, a holy war proclaimed against him. Gregory issued a summons to all the prelates of Europe for a General Council to be held in the Lateran palace, at Easter, in which he would pour out all his grievances against Frederick, and unite the whole church in pronouncing Anathema Maranatha against him. But the Emperor himself had appealed to a General Council against the Pope; one sitting in Rome, presided over by Gregory, was not the tribunal to which he would submit. The Count of Provence commissioned Romeo to go to Rome with a fleet conveying bishops and cardinals to attend the Council. But Frederick had prepared a powerful fleet in Sicily and Apulia, under the command of his son, Enzio. Pisa joined him with all her galleys. The Genoese and Provençal fleet met that of the Emperor off the island of Meloria; the heavily laden Genoese and Provençal vessels were worsted after a sharp conflict; three galleys were sunk, twenty-two were taken. Some of the prelates went down in the sunken galleys; among the prisoners were three cardinals, four archbishops, and six bishops.
Cardinal Otho was in the fleet, returning to Rome with English plunder. He had been collecting enormous sums by exactions on the clergy and freewill offerings for the replenishing of the Papal treasury, and the prosecution of the holy war against Frederick. All this now fell into the hands of the Imperialists. Romeo was not taken prisoner; he fought with determined courage, and even captured one of the hostile vessels, and brought it back to Marseilles.
Raymond Berenger died in 1245; by his will he had confided the regency to Romeo, along with the guardianship of his daughters.
Romeo assembled the Provençal nobles and the representatives of the chief towns, and made them swear allegiance to Beatrix, the daughter of his old master, who had been constituted heiress of Provence.
Romeo succeeded in getting her married to Charles of Anjou, brother of Louis IX. This was done with wise purpose, but events proved—events over which Romeo had no control—that it was a disastrous mistake.