Pope Sixtus, backed by the Orsini, was at war with the Colonna to the end of his reign; but once, on a day when there was truce, he seems to have said in anger that he cared not whom the Colonna served nor with whom they allied themselves. And Lorenzo Colonna, Protonotary Apostolic, with his brothers, took the Pope at his word, and they joined forces with the King of Naples, fortifying themselves in their stronghold of Marino, whence the eldest son of the family still takes his title. The Pope, seeing them in earnest and fearing King Ferdinand, sent an embassy of two cardinals to them, entreating them to be reconciled with the Church. But they answered that they would not, for his Holiness had given them permission to ally themselves with whom they pleased, and refused them money for service, and they said that they could not live without pay--a somewhat ironical statement for such men as the Colonna, who lived rather by taking than by giving an equivalent for anything received.
Then the Pope made war upon King Ferdinand, and when there had been much bloodshed, and plundering and burning on both sides, Prospero Colonna quarrelled with the Duke of Calabria, who was on Ferdinand's side and for whom he had been fighting, and came over to the Church, and so the Colonna were restored to favour, and the Pope made a treaty with the King against Venice, and so another year passed.
But after that the quarrel was renewed between Pope Sixtus and Lorenzo Colonna, on pretext that a certain part of the agreement to which they had come had not been executed by the Protonotary; and while the matter was under discussion, the Cardinal of Saint George, nephew of the great Count Jerome Riario, sent word privately to the Protonotary Colonna, warning him either to escape from Rome or to be on his guard if he remained, 'because some one was plotting against him, and hated him.' Wherefore Lorenzo shut himself up in the dwelling of Cardinal Colonna, between the Colonna palace and Monte Cavallo on the Quirinal hill, and many young men, attached to the great house, began to watch in arms, day and night, turn and turn about. And when this became known, the Orsini also began to arm themselves and keep watch at Monte Giordano. Scenting a struggle, a Savelli, siding with Colonna, struck the first blow by seizing forty horses and mules of the Orsini in a farm building on the Tivoli road; and immediately half a dozen robber Barons joined Savelli, and they plundered right and left, and one of them wrote a long and courteous letter of justification to the Pope. But Orsini retorted swiftly, 'lifting' horses and cattle that belonged to his enemies and making prisoners of their retainers. Among others he took two men who belonged to the Protonotary. And the latter, unable to leave Rome in safety, began to fortify himself in the Cardinal's house with many fighting men, and with many strange weapons, 'bombardelle, cerobottane,' and guns and catapults. Whereupon the Pope sent for Orsini, and commanded him, as the faithful adherent of the Church, to go and take the Protonotary prisoner to his house. But while Orsini was marshalling his troops with those of Jerome Riario, at Monte Giordano and in Campo de' Fiori, the Pope sent for the municipal officers of the city and explained that he meant to pardon the Protonotary if the latter would come to the Vatican humbly and of his own free will; and certain of these officers went to the Protonotary as ambassadors, to explain this. To them he answered, in the presence of Stephen Infessura, the chronicler who tells the story, that he had not fortified himself against the Church, but against private and dangerous enemies, against whom he had been warned, and that he had actually found that his house was spied upon by night; but that he was ready to carry out the terms of the old agreement, and finally, that he was ready to go freely to the Pope, trusting himself wholly to His Holiness, without any earnest or pledge for his safety, but that he begged the Pope not to deliver him into the hands of the Orsini. Yet even before he had spoken, the Orsini were moving up their men, by way of Saint Augustine's Church, which is near Piazza Navona. Nevertheless Colonna, the Protonotary, mounted his horse to ride over to the Vatican.