Despite the bishop's efforts, open warfare broke out between Ricimer and Anthemius again in 472. Ricimer, along with his barbarian mercenary units (including the soldiers of Odoacer), marched on Rome. Besieged, Anthemius took refuge in St. Peter's Basilica. Leo dispatched Olybrius to mediate a truce between Ricimer and Anthemius but, according to John Malalas, had sent a secret letter to Anthemius, urging him to kill Olybrius. Ricimer intercepted the letter, showed it to Olybrius, and had him proclaimed emperor. The siege lasted for five months. Ricimer finally entered the city and succeeded in separating the port on the Tiber from the Palatine Hill, starving the supporters of the emperor. Both sides appealed to the field army in Gaul, but the Burgundian commanding general of Gaul, Gundobad, supported his uncle Ricimer.