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.
But Fortune growing envious of the glory of Castruccio took away his life just at the time when she should have preserved it, and thus ruined all those plans which for so long a time he had worked to carry into effect, and in the successful prosecution of which nothing but death could have stopped him. Castruccio was in the thick of the battle the whole of the day; and when the end of it came, although fatigued and overheated, he stood at the gate of Fucecchio to welcome his men on their return from victory and personally thank them. He was also on the watch for any attempt of the enemy to retrieve the fortunes of the day; he being of the opinion that it was the duty of a good general to be the first man in the saddle and the last out of it. Here Castruccio stood exposed to a wind which often rises at midday on the banks of the Arno, and which is often very unhealthy; from this he took a chill, of which he thought nothing, as he was accustomed to such troubles; but it was the cause of his death. On the following night he was attacked with high fever, which increased so rapidly that the doctors saw it must prove fatal. Castruccio, therefore, called Pagolo Guinigi to him, and addressed him as follows:
“If I could have believed that Fortune would have cut me off in the midst of the career which was leading to that glory which all my successes promised, I should have laboured less, and I should have left thee, if a smaller state, at least with fewer enemies and perils, because I should have been content with the governorships of Lucca and Pisa. I should neither have subjugated the Pistoians, nor outraged the Florentines with so many injuries. But I would have made both these peoples my friends, and I should have lived, if no longer, at least more peacefully, and have left you a state without a doubt smaller, but one more secure and established on a surer foundation. But Fortune, who insists upon having the arbitrament of human affairs, did not endow me with sufficient judgment to recognize this from the first, nor the time to surmount it. Thou hast heard, for many have told thee, and I have never concealed it, how I entered the house of thy father whilst yet a boy—a stranger to all those ambitions which every generous soul should feel—and how I was brought up by him, and loved as though I had been born of his blood; how under his governance I learned to be valiant and capable of availing myself of all that fortune, of which thou hast been witness. When thy good father came to die, he committed thee and all his possessions to my care, and I have brought thee up with that love, and increased thy estate with that care, which I was bound to show. And in order that thou shouldst not only possess the estate which thy father left, but also that which my fortune and abilities have gained, I have never married, so that the love of children should never deflect my mind from that gratitude which I owed to the children of thy father. Thus I leave thee a vast estate, of which I am well content, but I am deeply concerned, inasmuch as I leave it thee unsettled and insecure. Thou hast the city of Lucca on thy hands, which will never rest contented under they government. Thou hast also Pisa, where the men are of nature changeable and unreliable, who, although they may be sometimes held in subjection, yet they will ever disdain to serve under a Lucchese. Pistoia is also disloyal to thee, she being eaten up with factions and deeply incensed against thy family by reason of the wrongs recently inflicted upon them. Thou hast for neighbours the offended Florentines, injured by us in a thousand ways, but not utterly destroyed, who will hail the news of my death with more delight than they would the acquisition of all Tuscany. In the Emperor and in the princes of Milan thou canst place no reliance, for they are far distant, slow, and their help is very long in coming. Therefore, thou hast no hope in anything but in thine own abilities, and in the memory of my valour, and in the prestige which this latest victory has brought thee; which, as thou knowest how to use it with prudence, will assist thee to come to terms with the Florentines, who, as they are suffering under this great defeat, should be inclined to listen to thee. And whereas I have sought to make them my enemies, because I believed that war with them would conduce to my power and glory, thou hast every inducement to make friends of them, because their alliance will bring thee advantages and security. It is of the greatest important in this world that a man should know himself, and the measure of his own strength and means; and he who knows that he has not a genius for fighting must learn how to govern by the arts of peace. And it will be well for thee to rule they conduct by my counsel, and to learn in this way to enjoy what my life-work and dangers have gained; and in this thou wilt easily succeed when thou hast learnt to believe that what I have told thee is true. And thou wilt be doubly indebted to me, in that I have left thee this realm and have taught thee how to keep it.”