Whilst Castruccio made peace with the Florentines, and strengthened his position in Lucca, he neglected no opportunity, short of open war, of increasing his importance elsewhere. It appeared to him that if he could get possession of Pistoia, he would have one foot in Florence, which was his great desire. He, therefore, in various ways made friends with the mountaineers, and worked matters so in Pistoia that both parties confided their secrets to him. Pistoia was divided, as it always had been, into the Bianchi and Neri parties; the head of the Bianchi was Bastiano di Possente, and of the Neri, Jacopo da Gia. Each of these men held secret communications with Castruccio, and each desired to drive the other out of the city; and, after many threatenings, they came to blows. Jacopo fortified himself at the Florentine gate, Bastiano at that of the Lucchese side of the city; both trusted more in Castruccio than in the Florentines, because they believed that Castruccio was far more ready and willing to fight than the Florentines, and they both sent to him for assistance. He gave promises to both, saying to Bastiano that he would come in person, and to Jacopo that he would send his pupil, Pagolo Guinigi. At the appointed time he sent forward Pagolo by way of Pisa, and went himself direct to Pistoia; at midnight both of them met outside the city, and both were admitted as friends. Thus the two leaders entered, and at a signal given by Castruccio, one killed Jacopo da Gia, and the other Bastiano di Possente, and both took prisoners or killed the partisans of either faction. Without further opposition Pistoia passed into the hands of Castruccio, who, having forced the Signoria to leave the palace, compelled the people to yield obedience to him, making them many promises and remitting their old debts. The countryside flocked to the city to see the new prince, and all were filled with hope and quickly settled down, influenced in a great measure by his great valour.
About this time great disturbances arose in Rome, owing to the dearness of living which was caused by the absence of the pontiff at Avignon. The German governor, Enrico, was much blamed for what happened–murders and tumults following each other daily, without his being able to put an end to them. This caused Enrico much anxiety lest the Romans should call in Ruberto, the King of Naples, who would drive the Germans out of the city, and bring back the Pope. Having no nearer friend to whom he could apply for help than Castruccio, he sent to him, begging him not only to give him assistance, but also to come in person to Rome. Castruccio considered that he ought not to hesitate to render the emperor this service, because he believed that he himself would not be safe if at any time the emperor ceased to hold Rome.
Leaving Pagolo Guinigi in command at Lucca, Castruccio set out for Rome with six hundred horsemen, where he was received by Enrico with the greatest distinction. In a short time the presence of Castruccio obtained such respect for the emperor that, without bloodshed or violence, good order was restored, chiefly by reason of Castruccio having sent by sea from the country round Pisa large quantities of corn, and thus removed the source of the trouble. When he had chastised some of the Roman leaders, and admonished others, voluntary obedience was rendered to Enrico. Castruccio received many honours, and was made a Roman senator. This dignity was assumed with the greatest pomp, Castruccio being clothed in a brocaded toga, which had the following words embroidered on its front: “I am what God wills.” Whilst on the back was: “What God desires shall be.”
During this time the Florentines, who were much enraged that Castruccio should have seized Pistoia during the truce, considered how they could tempt the city to rebel, to do which they thought would not be difficult in his absence. Among the exiled Pistoians in Florence were Baldo Cecchi and Jacopo Baldini, both men of leading and ready to face danger. These men kept up communications with their friends in Pistoia, and with the aid of the Florentines entered the city by night, and after driving out some of Castruccio’s officials and partisans, and killing others, they restored the city to its freedom. The news of this greatly angered Castruccio, and taking leave of Enrico, he pressed on in great haste to Pistoia. When the Florentines heard of his return, knowing that he would lose no time, they decided to intercept him with their forces in the Val di Nievole, under the belief that by doing so they would cut off his road to Pistoia. Assembling a great army of the supporters of the Guelph cause, the Florentines entered the Pistoian territories. On the other hand, Castruccio reached Montecarlo with his army; and having heard where the Florentines’ lay, he decided not to encounter it in the plains of Pistoia, nor to await it in the plains of Pescia, but, as far as he possibly could, to attack it boldly in the Pass of Serravalle. He believed that if he succeeded in this design, victory was assured, although he was informed that the Florentines had thirty thousand men, whilst he had only twelve thousand. Although he had every confidence in his own abilities and the valour of his troops, yet he hesitated to attack his enemy in the open lest he should be overwhelmed by numbers. Serravalle is a castle between Pescia and Pistoia, situated on a hill which blocks the Val di Nievole, not in the exact pass, but about a bowshot beyond; the pass itself is in places narrow and steep, whilst in general it ascends gently, but is still narrow, especially at the summit where the waters divide, so that twenty men side by side could hold it. The lord of Serravalle was Manfred, a German, who, before Castruccio became lord of Pistoia, had been allowed to remain in possession of the castle, it being common to the Lucchese and the Pistoians, and unclaimed by either–neither of them wishing to displace Manfred as long as he kept his promise of neutrality, and came under obligations to no one. For these reasons, and also because the castle was well fortified, he had always been able to maintain his position. It was here that Castruccio had determined to fall upon his enemy, for here his few men would have the advantage, and there was no fear lest, seeing the large masses of the hostile force before they became engaged, they should not stand. As soon as this trouble with Florence arose, Castruccio saw the immense advantage which possession of this castle would give him, and having an intimate friendship with a resident in the castle, he managed matters so with him that four hundred of his men were to be admitted into the castle the night before the attack on the Florentines, and the castellan put to death.
Castruccio, having prepared everything, had now to encourage the Florentines to persist in their desire to carry the seat of war away from Pistoia into the Val di Nievole, therefore he did not move his army from Montecarlo. Thus the Florentines hurried on until they reached their encampment under Serravalle, intending to cross the hill on the following morning. In the meantime, Castruccio had seized the castle at night, had also moved his army from Montecarlo, and marching from thence at midnight in dead silence, had reached the foot of Serravalle: thus he and the Florentines commenced the ascent of the hill at the same time in the morning. Castruccio sent forward his infantry by the main road, and a troop of four hundred horsemen by a path on the left towards the castle. The Florentines sent forward four hundred cavalry ahead of their army which was following, never expecting to find Castruccio in possession of the hill, nor were they aware of his having seized the castle. Thus it happened that the Florentine horsemen mounting the hill were completely taken by surprise when they discovered the infantry of Castruccio, and so close were they upon it they had scarcely time to pull down their visors. It was a case of unready soldiers being attacked by ready, and they were assailed with such vigour that with difficulty they could hold their own, although some few of them got through. When the noise of the fighting reached the Florentine camp below, it was filled with confusion. The cavalry and infantry became inextricably mixed: the captains were unable to get their men either backward or forward, owing to the narrowness of the pass, and amid all this tumult no one knew what ought to be done or what could be done. In a short time the cavalry who were engaged with the enemy’s infantry were scattered or killed without having made any effective defence because of their unfortunate position, although in sheer desperation they had offered a stout resistance. Retreat had been impossible, with the mountains on both flanks, whilst in front were their enemies, and in the rear their friends. When Castruccio saw that his men were unable to strike a decisive blow at the enemy and put them to flight, he sent one thousand infantrymen round by the castle, with orders to join the four hundred horsemen he had previously dispatched there, and commanded the whole force to fall upon the flank of the enemy. These orders they carried out with such fury that the Florentines could not sustain the attack, but gave way, and were soon in full retreat–conquered more by their unfortunate position than by the valour of their enemy. Those in the rear turned towards Pistoia, and spread through the plains, each man seeking only his own safety. The defeat was complete and very sanguinary. Many captains were taken prisoners, among whom were Bandini dei Rossi, Francesco Brunelleschi, and Giovanni della Tosa, all Florentine noblemen, with many Tuscans and Neapolitans who fought on the Florentine side, having been sent by King Ruberto to assist the Guelphs. Immediately the Pistoians heard of this defeat they drove out the friends of the Guelphs, and surrendered to Castruccio. He was not content with occupying Prato and all the castles on the plains on both sides of the Arno, but marched his army into the plain of Peretola, about two miles from Florence. Here he remained many days, dividing the spoils, and celebrating his victory with feasts and games, holding horse races, and foot races for men and women. He also struck medals in commemoration of the defeat of the Florentines. He endeavoured to corrupt some of the citizens of Florence, who were to open the city gates at night; but the conspiracy was discovered, and the participators in it taken and beheaded, among whom were Tommaso Lupacci and Lambertuccio Frescobaldi. This defeat caused the Florentines great anxiety, and despairing of preserving their liberty, they sent envoys to King Ruberto of Naples, offering him the dominion of their city; and he, knowing of what immense importance the maintenance of the Guelph cause was to him, accepted it. He agreed with the Florentines to receive from them a yearly tribute of two hundred thousand florins, and he send his son Carlo to Florence with four thousand horsemen.
Shortly after this the Florentines were relieved in some degree of the pressure of Castruccio’s army, owing to his being compelled to leave his positions before Florence and march on Pisa, in order to suppress a conspiracy that had been raised against him by Benedetto Lanfranchi, one of the first men in Pisa, who could not endure that his fatherland should be under the dominion of the Lucchese. He had formed this conspiracy, intending to seize the citadel, kill the partisans of Castruccio, and drive out the garrison. As, however, in a conspiracy paucity of numbers is essential to secrecy, so for its execution a few are not sufficient, and in seeking more adherents to his conspiracy Lanfranchi encountered a person who revealed the design to Castruccio. This betrayal cannot be passed by without severe reproach to Bonifacio Cerchi and Giovanni Guidi, two Florentine exiles who were suffering their banishment in Pisa. Thereupon Castruccio seized Benedetto and put him to death, and beheaded many other noble citizens, and drove their families into exile. It now appeared to Castruccio that both Pisa and Pistoia were thoroughly disaffected; he employed much thought and energy upon securing his position there, and this gave the Florentines their opportunity to reorganize their army, and to await the coming of Carlo, the son of the King of Naples. When Carlo arrived they decided to lose no more time, and assembled a great army of more than thirty thousand infantry and ten thousand cavalry–having called to their aid every Guelph there was in Italy. They consulted whether they should attack Pistoia or Pisa first, and decided that it would be better to march on the latter–a course, owing to the recent conspiracy, more likely to succeed, and of more advantage to them, because they believed that the surrender of Pistoia would follow the acquisition of Pisa.
In the early part of May 1328, the Florentines put in motion this army and quickly occupied Lastra, Signa, Montelupo, and Empoli, passing from thence on to San Miniato. When Castruccio heard of the enormous army which the Florentines were sending against him, he was in no degree alarmed, believing that the time had now arrived when Fortune would deliver the empire of Tuscany into his hands, for he had no reason to think that his enemy would make a better fight, or had better prospects of success, than at Pisa or Serravalle. He assembled twenty thousand foot soldiers and four thousand horsemen, and with this army went to Fucecchio, whilst he sent Pagolo Guinigi to Pisa with five thousand infantry. Fucecchio has a stronger position than any other town in the Pisan district, owing to its situation between the rivers Arno and Gusciana and its slight elevation above the surrounding plain. Moreover, the enemy could not hinder its being victualled unless they divided their forces, nor could they approach it either from the direction of Lucca or Pisa, nor could they get through to Pisa, or attack Castruccio’s forces except at a disadvantage. In one case they would find themselves placed between his two armies, the one under his own command and the other under Pagolo, and in the other case they would have to cross the Arno to get to close quarters with the enemy, an undertaking of great hazard. In order to tempt the Florentines to take this latter course, Castruccio withdrew his men from the banks of the river and placed them under the walls of Fucecchio, leaving a wide expanse of land between them and the river.
The Florentines, having occupied San Miniato, held a council of war to decide whether they should attack Pisa or the army of Castruccio, and, having weighed the difficulties of both courses, they decided upon the latter. The river Arno was at that time low enough to be fordable, yet the water reached to the shoulders of the infantrymen and to the saddles of the horsemen. On the morning of 10 June 1328, the Florentines commenced the battle by ordering forward a number of cavalry and ten thousand infantry. Castruccio, whose plan of action was fixed, and who well knew what to do, at once attacked the Florentines with five thousand infantry and three thousand horsemen, not allowing them to issue from the river before he charged them; he also sent one thousand light infantry up the river bank, and the same number down the Arno. The infantry of the Florentines were so much impeded by their arms and the water that they were not able to mount the banks of the river, whilst the cavalry had made the passage of the river more difficult for the others, by reason of the few who had crossed having broken up the bed of the river, and this being deep with mud, many of the horses rolled over with their riders and many of them had stuck so fast that they could not move. When the Florentine captains saw the difficulties their men were meeting, they withdrew them and moved higher up the river, hoping to find the river bed less treacherous and the banks more adapted for landing. These men were met at the bank by the forces which Castruccio had already sent forward, who, being light armed with bucklers and javelins in their hands, let fly with tremendous shouts into the faces and bodies of the cavalry. The horses, alarmed by the noise and the wounds, would not move forward, and trampled each other in great confusion. The fight between the men of Castruccio and those of the enemy who succeeded in crossing was sharp and terrible; both sides fought with the utmost desperation and neither would yield. The soldiers of Castruccio fought to drive the others back into the river, whilst the Florentines strove to get a footing on land in order to make room for the others pressing forward, who if they could but get out of the water would be able to fight, and in this obstinate conflict they were urged on by their captains. Castruccio shouted to his men that these were the same enemies whom they had before conquered at Serravalle, whilst the Florentines reproached each other that the many should be overcome by the few. At length Castruccio, seeing how long the battle had lasted, and that both his men and the enemy were utterly exhausted, and that both sides had many killed and wounded, pushed forward another body of infantry to take up a position at the rear of those who were fighting; he then commanded these latter to open their ranks as if they intended to retreat, and one part of them to turn to the right and another to the left. This cleared a space of which the Florentines at once took advantage, and thus gained possession of a portion of the battlefield. But when these tired soldiers found themselves at close quarters with Castruccio’s reserves they could not stand against them and at once fell back into the river. The cavalry of either side had not as yet gained any decisive advantage over the other, because Castruccio, knowing his inferiority in this arm, had commanded his leaders only to stand on the defensive against the attacks of their adversaries, as he hoped that when he had overcome the infantry he would be able to make short work of the cavalry. This fell out as he had hoped, for when he saw the Florentine army driven back across the river he ordered the remainder of his infantry to attack the cavalry of the enemy. This they did with lance and javelin, and, joined by their own cavalry, fell upon the enemy with the greatest fury and soon put him to flight. The Florentine captains, having seen the difficulty their cavalry had met with in crossing the river, had attempted to make their infantry cross lower down the river, in order to attack the flanks of Castruccio’s army. But here, also, the banks were steep and already lined by the men of Castruccio, and this movement was quite useless. Thus the Florentines were so completely defeated at all points that scarcely a third of them escaped, and Castruccio was again covered with glory. Many captains were taken prisoners, and Carlo, the son of King Ruberto, with Michelagnolo Falconi and Taddeo degli Albizzi, the Florentine commissioners, fled to Empoli. If the spoils were great, the slaughter was infinitely greater, as might be expected in such a battle. Of the Florentines there fell twenty thousand two hundred and thirty-one men, whilst Castruccio lost one thousand five hundred and seventy men.