Both sides prepared at once for war. Henry strengthened his frontier castles, and Louis called a great council of his kingdom, to which came his chief vassals, including the Counts of Flanders and Boulogne, whose long alliance with England made their action almost one of rebellion. There it was decided to join the war against the elder king of England. The long list of Henry's vassals who took his son's side, even if we deduct the names of some whose wavering inclination may have been fixed by the promises of lands or office which the younger Henry distributed with reckless freedom, reveals a widespread discontent in the feudal baronage. The turbulent lords of Aquitaine might perhaps be expected to revolt on every occasion, but the list includes the oldest names and leading houses of England and Normandy. Out of the trouble the king of Scotland hoped to recover what had been held of the last English king, and it may very well have seemed for a moment that the days of Stephen were going to return for all. The Church almost to a man stood by the king who had so recently tried to invade its privileges, and Henry hastened to strengthen himself with this ally by filling numerous bishoprics which had for a long time been in his hands. Canterbury was with some difficulty included among them. An earlier attempt to fill the primacy had failed because of a dispute about the method of choice, and now another failed because the archbishop selected refused to take office. At last in June Richard, prior of St. Martin's at Dover, was chosen, but his consecration was delayed for nearly a year by an appeal of the young king to the pope against a choice which disregarded his rights. The elder Henry had on his side also a goodly list of English earls: the illegitimate members of his house, Hamelin of Surrey, Reginald of Cornwall, and William of Gloucester; the earls of Arundel, Pembroke, Salisbury, Hertford, and Northampton; the son of the traitor of his mother's time, William de Mandeville, Earl of Essex; and William of Beaumont, Earl of Warwick, whose cousins of Leicester and Meulan were of the young king's party. The new men of his grandfather's making were also with him and the mass of the middle class.
The war was slow in opening. Henry kept himself closely to the defensive and waited to be attacked, appearing to be little troubled at the prospect and spending his time mostly in hunting. Early in July young Henry invaded Normandy with the Counts of Flanders and Boulogne, and captured Aumale, Eu, and a few other places, but the Count of Boulogne was wounded to the death, and the campaign came to an end. At the same time King Louis entered southern Normandy and laid siege to Verneuil, one ward of which he took and burnt by a trick that was considered dishonourable, and from which he fled in haste on the approach of Henry with his army. In the west, at the end of August, Henry's Brabantine mercenaries, of whom he is said to have had several thousand in his service, shut up a number of the rebel leaders in Dol. In a forced march of two days the king came on from Rouen, and three days later compelled the surrender of the castle. A long list is recorded of the barons and knights who were made prisoners there, of whom the most important was the Earl of Chester. A month later a conference was held at Gisors between the two parties, to see if peace were possible. This conference was held, it is said, at the request of the enemies of the king of England; but he offered terms to his sons which surprise us by their liberality after their failure in the war, and which show that he was more moved by his feelings as a father than by military considerations. He offered to Henry half the income of the royal domains in England, or if he preferred to live in Normandy, half the revenues of that duchy and all those of his father's lands in Anjou; to Richard half the revenues of Aquitaine; and to Geoffrey the possession of Britanny on the celebration of his marriage. Had he settled revenues like these on his sons when he nominally divided his lands among them, there probably would have been no rebellion; but now the king of France had much to say about the terms, and he could be satisfied only by the parcelling out of Henry's political power. To this the king of England would not listen, and the conference was broken off without result.
In England the summer and autumn of 1173 passed with no more decisive events than on the continent, but with the same general drift in favour of the elder Henry. Richard of Lucy, the justiciar and special representative of the king, and his uncle, Reginald of Cornwall, were the chief leaders of his cause. In July they captured the town of Leicester, but not the castle. Later the king of Scotland invaded Northumberland, but fell back before the advance of Richard of Lucy, who in his turn laid waste parts of Lothian and burned Berwick. In October the Earl of Leicester landed in Norfolk with a body of foreign troops, but was defeated by the justiciar and the Earl of Cornwall, who took him and his wife prisoners. The year closed with truces in both England and France running to near Easter time. The first half of the year 1174 passed in the same indecisive way. In England there was greater suffering from the disorders incident to such a war, and sieges and skirmishes were constantly occurring through all the centre and north of the land.
By the middle of the year King Henry came to the conclusion that his presence was more needed in the island than on the continent, and on July 8 he crossed to Southampton, invoking the protection of God on his voyage if He would grant to his kingdom the peace which he himself was seeking. He brought with him all his chief prisoners, including his own queen and his son's. On the next day he set out for Canterbury. The penance of a king imposed upon him by the Church for the murder of Thomas Becket he might already have performed to the satisfaction of the pope, but the penance of a private person, of a soul guilty in the sight of heaven, he had still to take upon himself, in a measure to satisfy the world and very likely his own conscience. For such a penance the time was fitting. Whatever he may have himself felt, the friends of Thomas believed that the troubles which had fallen upon the realm were a punishment for the sins of the king. A personal reconciliation with the martyr, to be obtained only as a suppliant at his tomb, was plainly what he should seek.
As Henry drew near the city and came in sight of the cathedral church, he dismounted from his horse, and bare-footed and humbly, forbidding any sign that a king was present, walked the remainder of the way to the tomb. Coming to the door of the church, he knelt and prayed; at the spot where Thomas fell, he wept and kissed it. After reciting his confession to the bishops who had come with him or gathered there, he went to the tomb and, prostrate on the floor, remained a long time weeping and praying. Then Gilbert Foliot, Bishop of London, made an address to those present, declaring that not by command or knowledge was the king guilty of the murder, but admitting the guilt of the hasty words which had occasioned it. He proclaimed the restoration of all rights to the church of Canterbury, and of the king's favour to all friends of the late archbishop. Then followed the formal penance and absolution. Laying off his outer clothes, with head and shoulders bowed at the tomb, the king allowed himself to be scourged by the clergy present, said to have numbered eighty, receiving five blows from each prelate and three from each monk. The night that followed he spent in prayer in the church, still fasting. Mass in the morning completed the religious ceremonies, but on Henry's departure for London later in the day he was given, as a mark of the reconciliation, some holy water to drink made sacred by the relics of the martyr, and a little in a bottle to carry with him.
The medieval mind overlooked the miracle of Henry's escape from the sanitary dangers of this experience, but dwelt with satisfaction on another which seemed the martyr's immediate response and declaration of forgiveness. It was on Saturday that the king left Canterbury and went up to London, and there he remained some days preparing his forces for the war. On Wednesday night a messenger who had ridden without stopping from the north arrived at the royal quarters and demanded immediate admittance to the king. Henry had retired to rest, and his servants would not at first allow him to be disturbed, but the messenger insisted: his news was good, and the king must know it at once. At last his importunity prevailed, and at the king's bedside he told him that he had come from Ranulf Glanvill, his sheriff of Lancashire, and that the king of Scotland had been overcome and taken prisoner. The news was confirmed by other messengers who arrived the next day and was received by the king and his barons with great rejoicing. The victory was unmistakably the answer of St. Thomas to the penance of Henry, and a plain declaration of reconciliation and forgiveness, for it soon became known that it was on the very day when the penance at Canterbury was finished, perhaps at the very hour, that this great success was granted to the arms of the penitent king.
The two spots of danger in the English insurrection were the north, where not merely was the king of Scotland prepared for invasion, but the Bishop of Durham, Hugh of Puiset, a connexion of King Stephen, was ready to assist him and had sent also for his nephew, another Hugh of Puiset, Count of Bar, to come to his help with a foreign force; and the east, where Hugh Bigod, the old earl of Norfolk, was again in rebellion and was expecting the landing of the Count of Flanders with an army. It was in the north that the fate of the insurrection was settled and without the aid of the king. The king of Scotland, known in the annals of his country as William the Lion, had begun his invasion in the spring after the expiration of the truce of the previous year, and had raided almost the whole north, capturing some castles and failing to take others such as Bamborough and Carlisle. In the second week of July he attacked Prudhoe castle in southern Northumberland. Encouraged perhaps by the landing of King Henry in England, the local forces of the north now gathered to check the raiding. No barons of high rank were among the leaders. They were all Henry's own new men or the descendants of his grandfather's. Two sheriffs, Robert of Stuteville of Yorkshire and Ranulf Glanvill of Lancashire, probably had most to do with collecting the forces and leading them. At the news of their arrival, William fell back toward the north, dividing up his army and sending detachments off in various directions to plunder the country. The English followed on, and at Alnwick castle surprised the king with only a few knights, his personal guard. Resistance was hopeless, but it was continued in the true fashion of chivalry until all the Scottish force was captured.
This victory brought the rebellion in England to an end. On hearing the news Henry marched against the castle of Huntingdon, which had been for some time besieged, and it at once surrendered. There his natural son Geoffrey, who had been made Bishop of Lincoln the summer before, joined him with reinforcements, and he turned to the east against Hugh Bigod. A part of the Flemish force which was expected had reached the earl, but he did not venture to resist. He came in before he was attacked, and gave up his castles, and with great difficulty persuaded the king to allow him to send home his foreign troops. Henry then led his army to Northampton where he received the submission of all the rebel leaders who were left. The Bishop of Durham surrendered his castles and gained reluctant permission for his nephew to return to France. The king of Scotland was brought in a prisoner. The Earl of Leicester's castles were given up, and the Earl of Derby and Roger Mowbray yielded theirs. This was on the last day of July. In three weeks after Henry's landing, in little more than two after his sincere penance for the murder of St. Thomas, the dangerous insurrection in England was completely crushed,—crushed indeed for all the remainder of Henry's reign. The king's right to the castles of his barons was henceforth strictly enforced. Many were destroyed at the close of the war, and others were put in the hands of royal officers who could easily be changed. It was more than a generation after this date and under very different conditions that a great civil war again broke out in England between the king and his barons.
But the war on the continent was not closed by Henry's success in England. His sons were still in arms against him, and during his absence the king of France with the young Henry and the Count of Flanders had laid siege to Rouen. Though the blockade was incomplete, an attack on the chief city of Normandy could not be disregarded. Evidently that was Henry's opinion, for on August 6 he crossed the channel, taking with him his Brabantine soldiers and a force of Welshmen, as well as his prisoners including the king of Scotland. He entered Rouen without difficulty, and by his vigorous measures immediately convinced the besiegers that all hope of taking the city was over. King Louis, who was without military genius or spirit, and not at all a match for Henry, gave up the enterprise at once, burned his siege engines, and decamped ignominiously in the night. Then came messengers to Henry and proposed a conference to settle terms of peace, but at the meeting which was held on September 8 nothing could be agreed upon because of the absence of Richard who was in Aquitaine still carrying on the war. The negotiations were accordingly adjourned till Michaelmas on the understanding that Henry should subdue his son and compel him to attend and that the other side should give the young rebel no aid. Richard at first intended some resistance to his father, but after losing some of the places that held for him and a little experience of fleeing from one castle to another, he lost heart and threw himself on his father's mercy, to be received with the easy forgiveness which characterized Henry's attitude toward his children.
There was no obstacle now to peace. On September 30 the kings of England and France and the three young princes met in the adjourned conference and arranged the terms. Henry granted to his sons substantial revenues, but not what he had offered them at the beginning of the war, nor did he show any disposition to push his advantage to extremes against any of those who had joined the alliance against him. The treaty in which the agreement between father and sons was recorded may still be read. It provides that Henry "the king, son of the king," and his brothers and all the barons who have withdrawn from the allegiance of the father shall return to it free and quit from all oaths and agreements which they may have made in the meantime, and the king shall have all the rights over them and their lands and castles that he had two weeks before the beginning of the war. But they also shall receive back all their lands as they had them at the same date, and the king will cherish no ill feeling against them. To Henry his father promised to assign two castles in Normandy suitable for his residence and an income of 15,000 Angevin pounds a year; to Richard two suitable castles and half the revenue of Poitou, but the interesting stipulation is added that Richard's castles are to be of such a sort that his father shall take no injury from them; to Geoffrey half the marriage portion of Constance of Britanny and the income of the whole when the marriage is finally made with the sanction of Rome. Prisoners who had made fine with the king before the peace were expressly excluded from it, and this included the king of Scotland and the Earls of Chester and Leicester. All castles were to be put back into the condition in which they were before the war. The young king formally agreed to the provision for his brother John, and this seems materially larger than that originally proposed. The concluding provisions of the treaty show the strong legal sense of King Henry. He was ready to pardon the rebellion with great magnanimity, but crimes committed and laws violated either against himself or others must be answered for in the courts by all guilty persons. Richard and Geoffrey did homage to their father for what was granted them, but this was excused the young Henry because he was a king. In another treaty drawn up at about the same time as Falaise the king of Scotland recognized in the clearest terms for himself and his heirs the king of England as his liege lord for Scotland and for all his lands, and agreed that his barons and men, lay and ecclesiastic, should also render liege homage to Henry, according to the Norman principle. On these conditions he was released. Of the king of France practically nothing was demanded.