Often after that, Dianora and Antonio too, seeing him ride by in attendance on Francesco, would admire with what address he sat his horse, with what grace he managed his lance, with what comeliness his sword; and indeed scarce any of his age dare meet him at the Barriere.  He was about eighteen years old when he made his first campaign.  For the Guelphs had driven the Ghibellines out of Pavia, and Visconti sought the help of his friends, among them of Francesco Guinigi.  Francesco gave Castruccio a company of foot, and marched with him to help Visconti:  and Castruccio won such reputation in that fight, that his name galloped through Lombardy, and when he returned to Lucca the whole city had him in respect.

Not long after, Guinigi fell sick; in truth he was about to die.  Seeing, then, that he had a son scarcely thirteen years old, called Pagolo, he gave him into Castruccio’s charge, begging him to show the same generosity to his son as he had received from him.  And all this Castruccio promised.

Now the head of the Guelph party in Lucca was a certain Signor Giorgio Opizi, who hoped when Francesco was dead to get the city into his power, so that when he saw Castruccio so well thought of and so strong, he began to speak secretly of a new tyranny, by which he meant the growing favour of Castruccio.  Pisa at this time was under the government of Uguccione della Faggiuola of Arezzo, whom the Pisans had chosen as their captain, but who had made himself their lord.  He had befriended certain Ghibellines banished from Lucca, and therefore Castruccio entered into secret treaty with him in order that these exiles might be restored.  So he furnished in Lucca the Tower of Honour, which was in his charge, in case he might have to defend it.  He met Uguccione on the night appointed, between Lucca and the hills towards Pisa, and, agreeing with him, Uguccione marched on the city to St. Peter’s Gate and set fire to it, while he attacked another on the other side of the town.  Meanwhile, his friends within the city ran about in the night calling To your arms, and filled the streets with confusion; so that Uguccione easily entered, and, having seized the city, caused all the Opizi to be murdered as well as all the Guelphs he could find.  Nor did he stop there, for he exiled one hundred of the best families, who immediately fled to Florence and Pistoja.  The Florentines, seeing the Guelph power tottering, put an army in the field, and met the Pisans and Lucchesi at Montecatini.  There followed the memorable battle called after that place, in which the Florentines lost some ten thousand men.[144] This was in 1315.  Now whether, as Villani says, Uguccione won that battle, or, as Machiavelli asserts, was sick, so that the honour fell to Castruccio, there was already of necessity much jealousy between the two captains; for certainly Castruccio had not called on Uguccione to make him Lord of Lucca, nor had Uguccione obeyed that call for mere love of Castruccio.