This was the final battle in the War of Breton Succession and here the principals were directly involved. Jean IV de Montfort and Charles de Blois each claimed succession to the duchy of Bretagne. Charles is killed here, ending the war of succession, since he had no heir to continue the fight.  For a look at the genealogical background of the conflict visit the Breton genealogy page.

Blois held Auray when it was besieged by Montfort. Montfort breached the city walls and continued the siege of the citadel. The citadel had agreed to surrender if relief did not reach them by 29 September but Charles de Blois mounted a relief army to come to Auray’s aid. Charles was supported by Bertrand du Guesclin and the count of Auxerre while Montfort was supported by Sir John Chandos and Robert Knolles, his English allies. In the fight Montfort had become an English client while Blois a French client, so both forces were respectively Anglo-Breton and Franco Breton.

Map 1 (from IGN carte randonnee 0821 OT) shows the lay of the land. Auray is on the Loc'h and was blockaded by sea from an English fleet. Du Guesclin arrived on the left bank of the river and camped near Kerzo (blue line). Charles de Blois was also on this side of the river. Du Guesclin moved into position on this side of the river across from Auray. Montfort was concerned with being caught between an attacking Franco-Breton army and Charles de Blois’ forces holding the citadel, so he withdrew from the city and positioned his forces across from Du Guesclin (red line).

Foissart: “Between Vannes and Auray, where the earl of Montfort was encamped, there are eight country leagues; so that news was soon brought to him that the lord Charles was advancing, with the finest body of men at arms, the handsomest equipped and the best ordered that had ever left France. This intelligence gave great joy to the English who were there; for they were eager for the fight. These companions, therefore, immediately set about putting their armour in good repair, and re-furbishing their lances, daggers, battle-axes, coats of mail, helmets, skull-caps, visors, swords, and all sorts of weapons, as they well imagined they should soon have use for them.”

“The commanders of the army then waited on the earl of Montfort; first sir John Chandos (whose advice he meant in particular to follow,) sir Eustace d’Ambreticourt, sir Robert Knolles, sir Hugh Calverly, sir Matthew Gournay. These knights and barons, having deliberated on their present situation, resolved that it would be most advantageous to quit their quarters early in the morning, and take the field. They might then consider on the best mode of action against the enemy, when they should have had more exact information concerning them. Orders were therefore given, that the whole army should, on the following morning, be ready armed and in battle array, as if they were immediately to begin the engagement.”

“This night passed quietly. On the morrow, which was a Saturday, the English and Bretons issued forth from their quarters, marching gaily in order of battle, to the rear of the castle of Auray, where they halted, and, having chosen a situation, declared they would wait the coming of their enemies. Almost immediately after day-break, the lord Charles and his army appeared.  … The troops of the lord Charles were in the best and handsomest order, and drawn up in the most brilliant manner that could be seen or imagined. They marched in such close order that one could not throw a tensional among them, but it must have struck upon the points of some of their lances, so stiffly did they carry them. The English took great pleasure in looking at them.”

“The French halted in this order in front of their enemies, and took their ground on an extensive heath. Their marshals gave strict charge that no one should quit his ranks without orders, and that there should be no tilting, jousts, or assaults. The men at arms, having halted, formed their line of battle, and made preparations for an immediate combat, as they expected nothing less, and were very desirous of it. The lord Charles de Blois, by the advice of sir Bertrand du Guesclin, (who was a great captain, and much praised and confided in by the Bretons,) formed his army again. He divided it into three battalions and a rear-guard. It seems to me, that sir Bertrand had the command of the first; and with him were numbers of knights and squires of Brittany. The earl of Auxerre had the second, with the earl of Joigny and many knights and squires from France. The third battalion was commanded by the lord Charles himself  … In the rear-guard were, the lords de Raix, de Rieux, de Tournemine, du Pont, and many good knights and squires. Each of these battalions was composed of a thousand men. The lord Charles de Blois entreated every one in the fairest manner, that they would loyally and discreetly assist him. He swore, upon his soul, and his hopes of Paradise, that it was for a just and right cause they were going to engage. He assured each, that, if they acquitted themselves well, he should feel himself ever obliged to them.”

“We must now speak of the dispositions of the English and Bretons, and in what manner they drew up their army. You first must understand that, though the earl of Montfort was the commander in chief, yet it was under the sole direction of sir John Chandos: for the king of England had thus settled it with the earl of Montfort. He had also ordered sir John Chandos to have especial regard to whatever concerned the interests of his son-in-law; for the earl of Montfort had received one of the king's daughters in marriage. In obedience to such orders, sir John Chandos advanced before the knights and squires of Brittany who were about the person of the earl of Montfort, and having well considered the dispositions of the French in his own mind, thought so highly of them, he could not remain silent, but said: “As God is my help, it appears to me that all the flower and honour of chivalry is there, most wisely and expertly drawn up.” He then added aloud to those knights who were within hearing: “Gentlemen, it is time that we form our line of battle; for the enemy have set us the example.” Those who heard him replied: “Sir, you say truly; and, as you are our commander, you will form us according to your wish; for there is none higher than yourself to look to, and you know much better than any one how to order such things.”

“Sir John Chandos formed three battalions and a rear-guard. He placed over the first, sir Robert Knolles, sir Walter Huet, and sir Richard Burley. The second battalion was under the command of sir Olivier de Clisson, sir Eustace d’Ambreticourt, and sir Matthew Gournay. The earl of Montfort had the third, which was to remain near his person. There were in each battalion five hundred men at arms, and four hundred archers. When he came to the rear-guard, he called sir Hugh Calverly to him, and said: “Sir Hugh, you will take the command of the rear-guard of five hundred men, and keep on our wing, without moving one step, whatever may happen, unless you shall see an absolute necessity for it; such as our battalions giving way, or being by accident broken: in that case, you will hasten to succour those who are giving way, or who may be in  need of help.”

After resisting, because of a perceived slight to his honor, Calverly was convinced to take command of the reserve. There were efforts to negotiate an agreement to avoid the battle but they came to naught, for several reasons. Foissart: “In the course of this evening, some English knights and squires earnestly begged of sir John Chandos that he would not listen to any overtures of peace between the earl of Montfort and lord Charles de Blois; for they had expended their whole fortune, and were so poor, that they hoped by means of a battle, either to lose their all or to set themselves up again. The knight assented to the request.” In addition, “John de Montfort is determined to risk the event of a combat. Have done, therefore, with all ideas of peace or agreements; for he will this day be duke of Brittany, or die in the field.”

On 29 September Blois moved his force across the river to the right bank. Montfort aligned his forces facing north to confront the Franco-Breton army. (Some sources initially place Montfort on the left bank who then moves his force across the river when Blois moves across the river.) Blois had the numerically superior force (about 4000 to Montfort’s 3000-3500). His troops were aligned between the la Chartreuse on his right and the river on his left. However, I don't think the line would extend as far as the river. The Chartreuse is on a plateau and there is a significant drop to the river elevation. Any force so aligned would be across the side of a steep hill, problematic at best. Blois was in the middle, du Guesclin on his right facing Knolles and Auxerre on the left facing Chandos. Map 1 shows the approximate positions, with Blois holding the blue and Montfort the red. Blois had been advised that the ground he chose was too marshy but he stuck with his position.

On the Anglo-Breton line, Montfort was in the center, Robert Knolles to the left and Chandos to the right, the river side of the line. While Blois had the numerical advantage, Montfort had the positional advantage.   

I have been able to find only one representation of the battlefield. It is from Fonssagrives and presented here.  After Blois crossed the the right bank of the Loc'h, the English realigned themselves to face him. Now their right flank was about at Penhoet and their line extended NW from there.

Foissart (chapter 227) offers an extensive description of the battle. The image of the battle is from Foissart. This is his text  in its entirety.

“A little before eight in the morning, the two armies advanced near to each other. It was a very fine sight, as I have heard those relate who saw it; for the French were in such close order that one could scarcely throw an apple among them, without its falling on a helmet or lance. Each man at arms carried his spear right before him, cut down to the length of five feet; a battle-axe, sharp, strong and well steeled, with a short handle, was at his side, or hung from his neck. They advanced thus handsomely a foots pace, each lord in array and among his people, with his banner or pennon before him, well knowing what they were to do. On the other hand, the English were drawn up in the handsomest order.”

“The Bretons, under the command of sir Bertrand du Guesclin, posted themselves with the banner opposite to the battalion of sir Robert Knolles and sir Walter Huet. The Bretons of either party placed the banners of their two lords, who was each called duke, opposite to the other.”

“In this first onset, there were hard blows between the lancemen, and a sharp scuffle. True it is, that the English archers shot well at the commencement; but their arrows hurt not, as the French were too well armed and shielded from them. Upon this, they flung away their bows; and, being light and able men, they mixed with the men at arms of their party, and attacked those of the French who had battle-axes. Being men of address and courage, they immediately seized several of these axes, with which they afterwards fought valiantly and successfully. There were many gallant feats of arms performed; many a struggle, many a capture, and many a rescue. You must know, that whoever had the misfortune to fall, found great difficulty to rise again unless he was speedily succoured.”

“The battalion of lord Charles marched straight to that of lord John de Montfort, which was very strong and deep. In his company were, the viscount de Rohan, the lords de Léon, Charles de Dinan, de Quintin, d’Ancenis, and de Rochfort, each with his banner displayed before him. The engagement between these two battalions was very severe and desperate, and well fought on both sides. That of the earl of Montfort was at first thrown into confusion; but sir Hugh Calverly, who was upon its wing with a good battalion of gallant men, perceiving them giving way and opening their ranks, drove the enemy back, and replaced everything by force of arms. This action was certainly of great use to them.”

“In another part of the plain, sir Olivier de Clisson, sir Eustace d’Ambreticourt, sir Matthew Gournay, and several other valiant knight and squires, fought valorously with the battalion of the earls of Auxerre and Joigny, which was very numerous and deep, and crowded with several able men at arms. Many bold actions were performed on both sides: prisoners and rescues were frequent. The French and Bretons fought in earnest with their battle-axes. The lord Charles showed himself a marvelously good knight, eagerly seeking for and engaging with his enemies. His adversary, the earl of Montfort, fought with equal gallantry: and each person spoke of them according to their deserts.”

“Sir John Chandos proved himself more able than his opponents: for he was at the same time bold and hardy, redoubted by his adversaries in battle, as well as wise and discreet in council, giving the clearest orders. He advised the earl in everything, and, in order to animate him and his people, said to them, “Do so and so: march to this side or to that.” The young earl of Montfort believed all he said, and followed his advice.”

“In another part, sir Bertrand du Guesclin, the lords du Pont, de Tournemine, d’Avaugour, de Raix, de Lohéac, de Malestroit, de Prie, and many other able knights and squires of Brittany and Normandy, who were there on the side of the lord Charles, fought very determinedly, and did many handsome deeds of arms. The battle was so warmly contested that all the battalions were engaged, except the rear-guard of the English, which sir Hugh Calverly commanded. This battalion kept always on one wing, and never engaged with any, but was solely occupied in recovering and bringing back to their ranks those who were thrown into confusion.”

“Among other knights, sir Olivier de Clisson played his part handsomely, and did marvels  with his battle-axe, by which he opened and cut through the ranks, so that none dared to approach him. Once, indeed, his eagerness brought him into great peril; for he advanced so forward that he had the battalion of the earls of Auxerre and Joigny upon him, and had hard work to extricate himself. He received in this affair a stroke of a battle-axe, which struck off the visor of his helmet; and its point entered his eye, which he afterwards lost. He was not, however, for this, a less gallant knight during the whole of the day.”

“Battalions and banners rushed against each other, and sometimes were overthrown, and then up again. Among the knights, sir John Chandos showed his ability, valorously fighting with his battle-axe: he gave such desperate blows, that all avoided him; for he was of great stature and strength, well made in all his limbs. He advanced to attack the battalion of the earl of Auxerre and the French. Many bold actions were performed; and, through the courage of himself and people, he drove this battalion before him, and threw it into such disorder that, in brief, it was discomfited. All their banners and pennons were thrown on the ground, torn and broken: their lords and captains were in the greatest danger; for they were not succoured by any, their people being fully engaged in fighting and defending themselves. To speak truly, when once an army is discomfited, those who are defeated are so much frightened, that if one fall, three follow his example, and to these three ten, and to ten thirty; and also, should ten run away, they will be followed by a hundred. Thus it was at the battle of Auray.”

“These lords shouted again and again their cries of war, as well as their banner bearers, which some who heard them answered; but others were too much in the rear, and from the from the greatness of the crowd could not advance, so that the earl of Auxerre was desperately wounded, and taken, under the pennon of Sir John Chandos: he gave his pledge as a prisoner, as well as the earl of Joigny and the lord de Prie, a great banneret in Normandy. The other battalions fought very valiantly, and the Bretons made a good appearance still. It must however, to speak loyally of this battle, be allowed, that they did not keep their line nor array (as it seemed) like the English and Bretons on the side of Montfort. The wing commanded by sir Hugh Calverly was to them, in this battle, of the greatest advantage. When the English and Bretons of the Montfort party perceived the French to be in confusion, they were much rejoiced. Some of the French had their horses got ready, which they mounted, and began to fly as fast as they could.”

“Sir John Chandos then advanced with a part of his company, and made for the battalion of sir Bertrand du Guesclin, where many courageous deeds were doing; but it had been already broken, and several good knights and squires slain. Many a hard blow was given by the battle-axes, and many a helmet opened, so that several were wounded and killed. To say the truth, neither sir Bertrand nor his people were able to withstand the strength of their adversaries. Sir Bertrand was made prisoner by an English squire, under the pennon of sir John Chandos. In this conflict, sir John received the pledge as prisoner, from a baron of Brittany, called the lord of Raix, a wonderfully hardy knight. After this, the Bretons and their battalion being broken, were as good as defeated: the others being in disorder, took to flight, each in the best way he could to save himself, except some good knights and squires of Brittany, who would not quit their sovereign, the lord Charles de Blois, preferring death to reproach. They collected themselves together, and rallied round him, fighting valiantly. The lord Charles and his companions kept their ground a long time, by their valour in defending themselves: at last, however, it was of no avail, for they were defeated and put to the rout by numbers; for the whole strength of the English was drawing towards them. The banner of the lord Charles was conquered, cast to the ground, and the bearer of it slain: he himself was also killed facing his enemies, as well as a bastard of his called the lord John de Blois, with many other knights and squires of Brittany.”

“It appears to me, that orders had been given to the English army, that if they should gain the battle, and the lord Charles were found or made prisoner, no ransom should be taken for him, but that they should kill him. In a similar case, the French and Bretons had given the like orders respecting the lord John de Montfort; for in this day each party wished, by battle, to put an end to the war.”

“When a pursuit took place, great slaughter and many mischiefs happened, and several good men were killed or made prisoners. The whole flower of chivalry, who had that day taken the side of lord Charles de Blois, were either prisoners or slain, particularly the bannerets of Brittany. Among the dead, lay the lord Charles de Dinan, the lords de Léon, d’Ancenis, d’Avaugour, de Lohéac, de Gargolle, de Malestroit, du Pont, and many whose names I cannot remember. There were made prisoners, the viscount de Rohan, sir Guy de Léon, the lord de Rochfort, de Raix, de Rieux, de Tournemine, sir Henry de Malestroit, sir Olivier de Mauny, the lords de Riville, de Franville, de Raineval, with several from Normandy, and many good knights and squires from France, with the earls of Auxerre and Joigny. In a word the defeat and loss were immense: numbers were slain in the field, as well as in the pursuit, which continued for eight good leagues, even as far as Vannes. A variety of accidents happened this day which had never come to my knowledge, and many a man was killed or made prisoner. Some fell into good hands, where they met with kind and civil masters.”

“This battle was fought near to Auray, in the year of our Lord 1364.”

“Sir John Chandos, sir Robert Knolles, sir Hugh Calverly and others, then approached to the earl of Montfort, and said to him, smiling; “My lord, praise God, and make good cheer, for this day you have conquered the inheritance of Brittany.” He bowed to them very respectfully, and then said, loud enough to be heard by all around him; “Sir John Chandos, it is to your valour and prudence that I am indebted for the good fortune of this day: this I know for a truth, as well as all those who are with me: I beg you will, therefore, refresh yourself out of my cup.  … Whilst they were thus together, two knights and two heralds returned, who had been sent to examine the dead bodies in the field, to know what was become of the lord Charles de Blois: for they were uncertain if he had been slain or not. They cried with a loud voice, “My lord, be of good cheer, for we have seen your adversary lord Charles de Blois among the dead.” Upon this, the earl of Montfort rose up and said, he wished to see him himself, for that, “he should have as much pleasure in seeing him dead as alive.” All the knights then present accompanied him to the spot where he was lying apart from the others, covered by a shield, which he ordered to be taken away, and looked at him very sorrowfully. After having paused a while, he exclaimed; “Ha, my lord Charles, sweet cousin, how much mischief has happened to Brittany from your having supported by arms your pretensions! God help me, I am truly unhappy at finding you in this situation, but at present this cannot be amended.” Upon which he burst into tears. Sir John Chandos, perceiving this, pulled him by the skirt, and said: “My lord, my lord, let us go away, and return thanks to God for the success of the day: for without the death of this person, you never would have gained your inheritance of Brittany.”

“The earl then ordered that lord Charles' body should be carried to Guingamp, which was immediately done with great respect, and he was most honourably interred. This was but his due, as he was a good, loyal, and valiant knight. His body was afterwards sanctified by the grace of God, and venerated as Saint Charles. Pope Urban V. who was the reigning pontiff, approved of it, by canonizing it; for it performed then, as it does to this day, many miracles.”

“…On the Monday morning, the earl of Montfort sent information to the city of Vannes, and to the neighbouring towns, that he should grant a truce for three days, in order that those slain in the battle might be buried in consecrated ground. This conduct was very pleasing to all.”

“… News of this victory was brought to the king of England; for the earl of Montfort had written to him on the fifth day after the battle of Auray, and sent the intelligence, with credential letters, by a pursuivant at arms, who had been in the engagement, to the town of Dover.  … Through this herald, and from some knights of both parties, I have been informed of the whole.”

Even though Edward III supported Montfort in his claim to the duchy, after the Treaty of Guerande, whereby Charles V recognized Montfort as duc de Bretagne, Montfort pledged fealty to France rather than England.

My sense is that Charles de Blois lost the duchy and his life due to poor field command ability. He consistently faced numerically weaker foes (La Roche Derrien, Restellou, Auray) and was out fought. Here at Auray he didn't take du Guesclin's warning about the choice of terrain. The way that Chandos and Blois handled their reserves is also telling. Chandos had a disciplined reserve that intervened in the fighting to stabilize the Montfort line, and once they achieved that objective, they withdrew to be able to respond to wherever the need arose again. Blois, on the other hand, had a weaker and less disciplined reserve. When it engaged, it stayed engaged and generally merged with whatever battalion was there. It did not maintain the flexibility to respond to pressure at different points of the line.

Another difference was that Chandos took overall charge of his force and not command of an individual battalion. This allowed him to maintain an overview of the battle and respond as circumstances directed. Blois, on the other hand, led his central battalion and was not able to direct his overall army.

In general, Blois had shorter lines of communication and actually held large parts of the duchy, so had its economic resources. He could receive French support without a Channel crossing. Montfort was a child when the conflict started and the English had the expense of maintaining field armies across the Channel. I think better generalship would have led to a different outcome.

en.wikipedia.org/wiki/Battle_of_Auray

Fonssagrives, E., Notice Historique sur la Ville d'Auray, Imprimerie de Basse Bretagne, Hennebont, 1991