Events like those enumerated above were favourable to the territorial extension of the Florentine Commune. Their progress would have been greater, had not an ancient feud among the nobles come to a bloody outbreak in the second decade of the thirteenth century. The effect of this factious contest, which was embittered by religious animosity and the quarrel of Frederic II. with the Pope, was to enfeeble the nobility, and react mischievously on the people. The murder of Messer Buondelmonte de’ Buondelmonti at the entrance of the old bridge in 1215 is celebrated in history and poetry as the presumed origin of the hostile factions of Guelf and Ghibelline. A stone cross in the small square, called, from the junction of three streets, the Trebbio, commemorates the victory of the orthodox citizens, led by Peter Martyr of Verona, against the Patarian heretics. About 1247 the most violent civil war raged. Although the Ghibelline faction had the upper hand at first, and Frederick of Antioch, the Emperor’s son and Imperial Vicar in Tuscany, drove out the Guelf nobility, the tables were turned when heavy losses overtook Frederick in Lombardy and were followed by his death. The year of Frederick’s death, 1250, marks the victory of the Guelfic cause in Florence, for although their adversaries had a momentary triumph they could not hold out, and the city so famous under the Salieri for its devotion to the Emperor, became the stronghold of the Guelfs. This decisive change, which brought constitutional changes with it, took place towards the end of October 1250, a little before the Emperor’s death.