The prince kept his Christmas at Bordeaux. Even during the winter his troops remained active. Most of the Agenais was conquered by January, 1356, while in February the capture of Périgueux opened up the way of invasion northwards. Meanwhile the prince mustered his forces for a vigorous summer campaign. While the towns on the Isle and the Lot were yielding to his son, Edward III. was avenging the capture of Berwick by a winter campaign in the Lothians. Before the end of January, 1356, Berwick was once more in his hands. Thence he passed to Roxburgh, where Edward Balliol surrendered to him all his rights over the Scottish throne. Thenceforth styling himself no longer overlord but King of Scotland, Edward mercilessly harried his new subjects. But storms dispersed the English victualling ships, and Edward's men could not live in winter on the country that they had made a wilderness. In a few weeks they were back over the border, though their raid was long remembered in Scottish tradition as the Burnt Candlemas.

Another breach between Charles of Navarre and his father-in-law again opened to the English the way to Normandy. John lost patience at Charles's renewed intrigues, and in April arrested him and his friends at Rouen. Thereupon his brother, Philip of Navarre, rose in revolt. With him were many of the Norman lords, including Geoffrey of Harcourt, lord of Saint-Sauveur. The English were once more invited to Normandy, and on June 18 Lancaster landed at La Hougue with the double mission of aiding the Norman rebels and establishing John of Montfort, then arrived at man's estate, in his Breton duchy. It was the first English invasion of northern France during the war, in which they had, as in Brittany, the co-operation of a strong party in the land. The Navarre and Harcourt influence at once secured them the Côtentin. Meanwhile, however, the French were besieging the fortresses of the county of Evreux. With the object of relieving this pressure, Lancaster, immediately after his landing, marched into the heart of Normandy, and soon reached Verneuil. It looked for the moment as if he were destined to emulate the exploits of Edward II. in 1346. But he abruptly turned back, leaving the county of Evreux to fall into French hands. The permanent result of his intervention was to reduce Normandy to a state of anarchy nearly as complete as that of Brittany. In the autumn Lancaster at last made his way to the land of which he had had nominal charge since the previous year. He left Philip of Navarre as commander in Normandy, and the war was supported from local resources. The Côtentin being in friendly hands, Lancaster attacked the strongholds of the Blois party, which had hitherto been exempt from the war. In October he laid siege to Rennes and was detained before its walls until July, 1357, when he agreed to desist from the attack in return for a huge ransom. Lancaster then established young Montfort as duke. At the same time Charles of Blois, released from his long imprisonment, once more reappeared in his wife's inheritance, though, as his ransom was still but partly paid, his scrupulous honour compelled him to abstain from personal intervention in the war. Thus Brittany got back both her dukes.

The northern operations in 1356 sink into insignificance when compared with the exploits of the Black Prince in the south. After the capture of Périgueux, there had been some idea of the prince making a northward movement and joining hands with Lancaster on the Loire. When Lancaster retired from Verneuil, however, the Black Prince was still in the valley of the Dordogne. Even when all was ready, attacks on the Gascon duchy compelled him to divert a large portion of his army for the defence of his own frontiers. Not until August 9 was he able to advance from Périgueux to Brantôme into hostile territory. It was a month too late to co-operate with Lancaster, and the 7,000 men, who followed his banners, were in equipment rather prepared for a raid than for a systematic conquest.

Edward's outward march was in a generally northerly direction. Leaving Limoges on his right, he crossed the Vienne lower down the stream, and thence he led his troops over the Creuse at Argenton and over the Indre at Châteauroux. When he traversed the Cher at Vierzon, his followers rejoiced that they had at last got out of the limits of the ancient duchy of Guienne and were invading the actual kingdom of France. On penetrating beyond the Cher into the melancholy flats of the Sologne, the prince encountered the first serious resistance. He then turned abruptly to the west, and chased the enemy into the strong castle of Romorantin, which he captured on September 3. There he heard that John of France, who had gathered together a huge force, was holding the passages over the Loire. Edward marched to meet the enemy, and on September 7 reached the neighbourhood of Tours, where he tarried in his camp for three days. But the few bridges were destroyed or strongly guarded, and the men-at-arms found it quite impossible to make their way over the broad and swift Loire. Moreover the news came that John had crossed the river near Blois, and was hurrying southwards. Thereupon the Black Prince turned in the same direction, seeing in this southward march his best chance of getting to close quarters. The French host was enormously the superior in numbers, but after Morlaix, Mauron, and Crecy, mere numerical disparity weighed but lightly on an English commander.

For some days the armies marched in the same direction in parallel lines, neither knowing very clearly the exact position of the other. On September 14 Edward reached Châtelherault on the Vienne. His troops were weary and war-worn, and his transport inordinately swollen by spoils. He rested two days at Châtelherault, but was again on the move on hearing that the enemy was at Chauvigny, situated some twenty miles higher up the Vienne. Edward at once started in pursuit, only to find that the French had retired before him to Poitiers, eighteen miles due west of Chauvigny. Careless of his convoy, he hurried across country in the hope of catching the elusive enemy, but was only in time to fight a rear-guard skirmish at a manor named La Chaboterie, on the road from Chauvigny to Poitiers, on September, 17. That night the English lay in a wood hard by the scene of action, suffering terribly from want of water. Next day, Sunday, September 18, Edward pursued the French as near as he could to Poitiers, halting in battle array within a league of the town. A further check on his impatience now ensued. Innocent VI.'s legate, the Cardinal Talleyrand, brother of the Count of Périgord, who was with the French army, crossed to the rival host with an offer of mediation. Edward received the cardinal courteously and spent most of the day in negotiations. But the French showed no eagerness to bring matters to a conclusion, and as every hour reinforcements poured into the enemy's camp the scanty patience of the English was exhausted. They declared that the legate's talk about saving the effusion of Christian blood was only a blind to gain time, so that the French might overwhelm them. Edward broke off the negotiations, and, retiring to a position more remote from the enemy, passed the night quietly. Early next morning the cardinal again sought to treat, but this time his offers were rejected. On his withdrawal, the French attack began.

The topographical details of the battle of Poitiers of September 19, 1356, cannot be determined with certainty. We only know that the place of the encounter was called Maupertuis, which is generally identified with a farm now called La Cardinerie, some six miles south-east of Poitiers, and a little distance to the north of the Benedictine abbey of Nouaille. The abbey formed the southern limit of the field. On the west the place of combat was skirted by the little river Miausson, which winds its way through marshes in a deep-cut valley, girt by wooded hills. The French left their horses at Poitiers, having resolved, perhaps on the advice of a Scottish knight, Sir William Douglas, to fight on foot, after the English and Scottish fashion, and as they had already fought at Mauron and elsewhere. As at Mauron, a small band of cavalry was retained, both for the preliminary skirmishing which then usually heralded a battle, and in the hope of riding down some of the archers. But the French did not fully understand the English tactics, and took no care to combine men-at-arms with archers or crossbowmen, though these were less important against an army weak in archers and largely consisting of Gascons. Of the four "battles" the first, under the Marshals Audrehem and Clermont, included the little cavalry contingent; the second was under Charles, Duke of Normandy, a youth of nineteen; the third under the Duke of Orleans, the king's brother; and the rear was commanded by the king.

The English army spent the night before the battle beyond the Miausson, but in the morning the prince, fearing an ambuscade behind the hill of Nouaillé on the east bank, abandoned his original position and crossed the stream in order to occupy it. He divided his forces into three "battles," led respectively by himself, Warwick, and William Montague, since 1343 by his father's death Earl of Salisbury. Though he found no enemy there, he remained with his "battle" on the hill, because it commanded the slopes to the north over on which the French were now advancing. His remote position threw the brunt of the fighting upon the divisions of Warwick and Salisbury. They were stationed side by side in advance of him on ground lower than that held by him, but higher than that of the enemy, and beset with bushes and vineyards which sloped down on the left towards the marshes of the Miausson. Some distance in front of their position, a long hedge and ditch divided the upland, on which the "battles" of Warwick and Salisbury were stationed, from the fields in which the French were arrayed. At its upper end, remote from the Miausson, where Salisbury's command lay, the hedge was broken by a gap through which a farmer's track connected the fields on each side of it. The first fighting began when the English sent a small force of horsemen through the gap to engage with the French cavalry beyond. While Audrehem, on the French right, suspended his attack to watch the result, Clermont made his way straight for the gap, hoping to take Salisbury's division, on the upper or right-hand station, in flank. Before he reached the gap, however, he found the hedge and the approaches to the cart-road held in force by the English archers. Meanwhile the mail-clad men and horses of Audrehem's cavalry had approached dangerously near the left of the English line, where Warwick was stationed. Their complete armour made riders and steeds alike impervious to the English arrows, until the prince, seeing from his hill how things were proceeding, ordered some archers to station themselves on the marshy ground near the Miausson, in advance of the left flank of the English army. From this position they shot at the unprotected parts of the French horses, and drove the little band of cavalry from the field. By that time Clermon's attack on the gap had been defeated, and so both sections of the first French division retired.

Then came the stronger "battle" of the eldest son of the French king. The fight grew more fierce, and for a long time the issue remained doubtful. The English archers exhausted their arrows to little purpose, and the dismounted French men-at-arms, offering a less sure mark than the horsemen, forced their way to the English ranks and fought a desperate hand-to-hand conflict with them. At last the Duke of Normandy's followers were driven back. Thereupon a panic seized the division commanded by the Duke of Orleans, which fled from the field without measuring swords with the enemy. The victors themselves were in a desperate plight. Many were wounded, and all were weary, especially the men-at-arms encased in heavy plate mail. The flight of Orleans gave them a short respite: but they soon had to face the assault of the rear battle of the enemy, gallantly led by the king. "No battle," we are told, "ever lasted so long. In former fights men knew, by the time that the fourth or the sixth arrow had been discharged, on which side victory was to be. But here a single archer shot with coolness a hundred arrows, and still neither side gave way."[1] At last the bowmen had only the arrows they snatched from the bodies of the dead and dying, and when these were exhausted, they were reduced to throwing stones at their foes, or to struggle in the mêlée, with sword and buckler, side by side with the men-at-arms. But the Black Prince from his hill had watched the course of the encounter, and at the right moment, when his friends were almost worn out, marched down, and made the fight more even. Before joining himself in the engagement, Edward had ordered the Captal de Buch, the best of his Gascons, to lead a little band, under cover of the hill, round the French position and attack the enemy in the rear. At first the Anglo-Gascon army was discouraged, thinking that the captal had fled, but they still fought on. Suddenly the captal and his men assaulted the French rear. This settled the hard fought day. Surrounded on every side, the French perished in their ranks or surrendered in despair. King John was taken prisoner, fighting desperately to the last, and with him was captured his youngest son Philip, the future Duke of Burgundy, a boy of twelve, whose epithet of "the Bold" was earned by his precocious valour in the struggle. Before nightfall the English host had sole possession of the field, and the best fought, best directed, and most important of the battles of the war ended in the complete triumph of the invaders.

[1] Eulogium Hist., iii., 225.

As after Crecy, the victors were too weak to continue the campaign. Next day they began their slow march back to their base. On October 2 Edward reached Libourne, and a few days later conducted the captive king into the Gascon capital. They were soon followed by the Cardinal Talleyrand on whose insistence the prince agreed to resume negotiations. On March 23, 1357, a truce to last until 1359 was arranged at Bordeaux. On May 24 the prince led the vanquished king through the streets of London.