While the Florentines were thus anxious, fortune disclosed the means of securing themselves against the patriarch's malevolence. The republic everywhere exercised the very closest espionage over epistolary communication, in order to discover if any persons were plotting against the state. It happened that letters were intercepted at Monte Pulciano, which had been written by the patriarch to Niccolo without the pope's knowledge; and although they were written in an unusual character, and the sense so involved that no distinct idea could be extracted, the obscurity itself, and the whole aspect of the matter so alarmed the pontiff, that he resolved to seize the person of the cardinal, a duty he committed to Antonio Rido, of Padua, who had the command of the castle of St. Angelo, and who, after receiving his instructions, soon found an opportunity of carrying them into effect. The patriarch, having determined to go into Tuscany, prepared to leave Rome on the following day, and ordered the castellan to be upon the drawbridge of the fortress in the morning, for he wished to speak with him as he passed. Antonio perceived this to be the favorable moment, informed his people what they were to do, and awaited the arrival of the patriarch upon the bridge, which adjoined the building, and might for the purpose of security be raised or lowered as occasion required. The appointed time found him punctual; and Antonio, having drawn him, as if for the convenience of conversation, on to the bridge, gave a signal to his men, who immediately raised it, and in a moment the cardinal, from being a commander of armies, found himself a prisoner of the castellan. The patriarch's followers at first began to use threats, but being informed of the pope's directions they were appeased. The castellan comforting him with kind words, he replied, that "the great do not make each other prisoners to let them go again; and that those whom it is proper to take, it is not well to set free." He shortly afterward died in prison. The pope appointed Lodovico, patriarch of Aquileia, to command his troops; and, though previously unwilling to interfere in the wars of the league and the duke, he was now content to take part in them, and engaged to furnish four thousand horse and two thousand foot for the defense of Tuscany.