The Barons' War was a civil war fought between January 1264 and September 1267, although the later Dictum of Kenilworth was to legally define the conflict as lasting from the 4th April 1264 to the 16th September 1265. The war was fought between king Henry III and his supporters and a group of barons acting under the leadership of Simon de Montfort.

The Origins of the War

The war was in reality the culmination of the Baronial Revolt that been simmering since 1258, when the baronial opposition to Henry III had been demanding a greater degree of consultation and involvement in the government as enshrined in the Provisions of Oxford of 1258 and the associated Provisions of Westminster of 1259, which a reluctant king had been forced to accept.

On the 13th April 1261 Pope Alexander IV issued a papal bull absolving Henry III and others from their oaths to uphold the Provisions of Oxford, after which the king simply ignored the requirements of the provisions and spent the next two years strengthening his personal control of the government. Naturally as he did so, Henry III alienated a number of his barons, most specifically a number of Lords Marcher lead by Roger Clifford, who felt particularly threatened by the efforts of the Lord Edward, himself the Earl of Chester to extend his authority across Wales.

This group of disillusioned barons invited Simon de Montfort to return from France to assist them in their dispute with the crown. Montfort had been amongst the early leaders of the Baronial Revolt, but had left the country in disgust in 1261 when reform seemed a distant prospect.Now he agreed to return to England, believing that the prospects for the reform of government had now improved.

They all met at Oxford in May 1263, and issued an ultimatum to Henry III demanding his adherence to the Provisions. Their ultimatum was rejected, so the barons secured the Welsh Marches and the Severn valley and began attacking the estates of the king's supporters. Simon de Montfort marched to Reading and then to the Cinque Ports whilst London rose in favour of the revolt. On the 15 July 1263 Henry III gave in, and agreed to re-instate the Provisions effectively placing the government in the hands of the rebels.

As always, Henry's submission was merely a tactical retreat, and involved no change of policy. In an effort to undermine support for the revolt, he adopted a policy of returning lands previously confiscated by the crown for various misdemeanors in recent years. In this he was successful, with over a 100 such restorations accomplished in the last few months of the year, leading to a gradual loss of interest in the cause of reform.

Henry then offered to settle the whole dispute over the issue of the Provisions of Oxford by submitting to the mediation of Louis IX of France. It was possibly this steady withdrawal of support that caused the baronial leaders to agree to Henry's offer of mediation, believing that it at least offered an opportunity of achieving at least some measure of reform. They were however to be disappointed as Louis IX's judgement, delivered in the Mise of Amiens on the 23rd January 1264 ruled entirely in Henry's favour and declared the Provisions invalid and an unwarranted trespass on the prerogative of the king.

The Outbreak of War

Simon de Montfort and many others, simply refused to accept the decision embodied in the Mise of Amiens, believing that there had been no genuine attempt at mediation, and prepared for war. Together with his sons, he planned an attack on the Marcher Lordship of Radnor, held by Roger Mortimer, one of the king's key supporters. However, in February the Lord Edward landed in Kent and quickly made his way to Gloucester, he soon drove the rebel Barons out of the Welsh Marches and joined the king at Oxford. There Henry had summoned his supporters to gather on the 30th March.

Meanwhile the baronial forces were converging at Northampton, with the exception of Simon himself who was recovering at Kenilworth castle from a fall from his horse. The Lord Edward left Oxford for Northampton and on the 6th April 1264 he took Northampton and on the following day the castle itself surrendered; Edward captured many of the baronial leaders including the younger Simon and Peter de Montfort. Henry and Edward then proceeded to attack the estates of baronial supporters in the midlands.

A recuperated Simon de Montfort refused to be discouraged by this reverse and made for London from where he and Gilbert the Red, Earl of Gloucester went to lay siege to Rochester Castle; whose strategic importance lay in its control over the road between London and Dover. On the 18th April Simon de Montfort and Gilbert the Red stormed the town of Rochester and by the next day they had taken the castle outer walls leaving only the great keep remaining in royalist hands.

Henry could not risk being cut off from the continent, and so he and the Lord Edward came south with their army and relieved Rochester, whilst Simon and Gilbert retreated back to London. This allowed Henry and Edward to take Tonbridge Castle and secure control of the Cinque Ports with the exception of Dover where Reginald de Grey still held out for the barons.

Back in London, Simon de Montfort rallied his forces and in May marched from London to Sussex to confront the king. Last ditch attempts were made to reach a compromise by the rebels but their embassy was contemptuously dismissed. On the 13th May the rebels formally withdrew their homage and fealty to the king and prepared for battle.

The resulting battle of Lewes was fought on the 14th May 1264 when Simon de Montfort despite being outnumbered won a stunning victory over the royalist forces. The following day both Henry III and the Lord Edward surrendered to Montfort and signed the Mise of Lewes, a form of peace that included acceptance of the Provisions of Oxford.

Now in the custody of the rebel barons, Henry was taken to London whilst Edward and Richard of Cornwall were taken to Montfort's stronghold at Kenilworth. Other key royalists however managed to escape; William de Valence and John de Warenne fled the battlefield to Pevensey where they took a ship to France.

Montfort in control

A Parliament was convened in June which appointed the triumvirate of Simon de Montfort, Gilbert the Red and Stephen Bersted the Bishop of Chichester to run the country. They drew up a form of government, under which a council of nine would be appointed to advise the king, three of whom would always be in attendance on the king to advise him on his every decision.

Nothing in this form of government implied that Henry III had been in any way deposed, this particular set of revolutionaries sought merely to reform the government of the king not to replace it. Every act of the new regime was carried out in the king's name, but it soon became apparent that nothing happened without the approval of Simon de Montfort, who became the effective ruler of the country.

In August both Henry and Edward were brought to Canterbury where on the 12th August they signed the Peace of Canterbury which confirmed the form of government previously adopted in June. Their acquiescence was of course, forced on them by circumstance, and neither had the slightest intention of abiding by the terms of the Peace should circumstances change.

Meanwhile the queen, Eleanor of Provence and a number of other exiles remained at Boulogne where plans were conceived for an invasion. During September 1264 efforts were made to reach an accommodation with the exiles that had gathered at Boulogne; an offer was made to submit the terms of the Peace of Canterbury to the mediation of a committee of two Englishmen and two Frenchmen under the chairmanship of the papal legate.

The papal legate in question was Cardinal Gui of Sabina, appointed by the Pope at the suggestion of king Louis. The cardinal promptly demanded admittance to England and the renunciation of the Provisions. Naturally Montfort and his allies refused, so on the 21st October the cardinal excommunicated the rebels and placed them under interdict. He might well have done more to undermine the rebellion had he not been recalled to Rome in December on the more pressing business of his elevation to the papacy as Pope Clement IV.

This brought to an end any ideas of a compromise with the royalist exiles at Boulogne who began forming plans to invade England. With an invasion seemingly imminent Montfort spent most of the autumn subduing the royalist barons of the Welsh marches. On the 12th December Montfort forced them to accept the Pact of Worcester (to which the Lord Edward was also a party) when the like of Roger Mortimer agreed to depart for Ireland for a year and a day.

In January 1265 a parliament was convened at Westminster, which was later to attract the reputation of being the first true Parliament, due to the presence of representatives from the boroughs. This parliament confirmed the form of government previously agreed and on the 11th March both Henry III and the Lord Edward made solemn declarations to uphold the Provisions of Oxford. Nine bishops who had previously supported the king were excommunicated, and every freeman in the land was ordered to his oath of homage to the king in order to emphasize the new regime's fidelity to the principles of the monarchy.

The Unravelling of the Revolt

In an effort to bolster support for his new regime Simon de Montfort sought an alliance with Llywelyn ap Gruffudd, ruler of Gwynedd in order to secure his western borders and act as a counterweight against the royalist barons in the march. Unfortunately for Simon, the Lords Marcher who had initiated the revolt in the first place because they feared that the king and Lord Edward intended to undermine their privileged status in the Welsh Marches saw Llywelyn as an equal if not greater threat.

This was particularly of concern to Gilbert the Red who was not only Earl of Gloucester, but also held the Marcher Lordship of Glamorgan which had already been a source of conflict with Llywelyn. Gilbert had also become disenchanted with the way that the new form of government established in the aftermath of Lewes had rapidly become dominated by Simon de Montfort and his relations.

Now inspired to switch allegiances, Gilbert was perfectly placed to do so, as his brother Thomas de Clare was in charge of the imprisonment of the Lord Edward, and hence it was an easy matter to arrange his escape. On the 28th May the Lord Edward duly made his escape, and once free soon made contact with Gilbert and other Lords Marcher such as Roger Mortimer. They were soon joined by William de Valence and others from Boulogne who had sailed from France and landed at Pembroke.

Under the command of Edward the royalist forces soon took command of the Welsh Marches and forced Simon de Montfort to battle near the town of Evesham. At the battle of Evesham on the 4th August 1265 the royalist army scattered the rebels and Montfort together with thirty or so of his supporters were all slaughtered on the battlefield.

King Henry III was freed from his captors and was once more in charge of his own government. On the 16th September 1265 a general peace was proclaimed and all acts carried out by Simon de Montfort in the king's name formally annulled. On the following day Henry announced the confiscation of the estates of many of the rebels. This latter decision served only to prolong the revolt, as the disinherited rebels had now had no incentive to lay down their arms and nothing to lose by continued resistance. For one thing, the city of London, one of the mainstays of the revolt had not yet opened its gates for the king.

A month later, in October 1265 London finally surrendered to the king, but did not escape punishment for its support of the rebellion; the Lord Mayor Thomas FitzThomas was imprisoned, a number of other prominent citizens fined and the city itself fined a total of 20,000 marks. The city was placed under royal control and it was not for another five years until November 1270, that London was permitted to resume its former privileges. With London subdued, the wife of Montfort, the Countess of Leicester surrendered Dover Castle and left England on the 28th October, never to return.

The feudal host was summoned to Northampton on the 13th December 1265 to begin an assault on Kenilworth Castle, but Edward diverted much of the assembled force to the Isle of Axholme1 where the younger Simon de Montfort was holding out. Axholme surrendered by Christmas and the younger Simon agreed to leave England in return for a pension. Further surrenders of baronial strongholds continued in the new year, by January Sandwich had surrendered and Winchelsea followed suit in March; but despite these successes the country remained divided and sporadic fighting continued.

The Resolution of the War

The final resolution of the conflict was really the work of the new papal legate Ottobuono Feschi. He arrived in England in November 1265 and on the 1st December held an ecclesiastical council in London, which eventually suspended four of the five bishops that had been most supportive of Simon de Montfort, and ordered them to attend the papal court in Rome.2 He then turned his attention to secular matters as many of the supporters of the Baronial movement remained at large.

Whilst the Lord Edward, with the support of men such as Roger Leyburn and Henry of Alamain had achieved some success in moping up much of the resistance, most notably on the 15th May 1266 when Henry of Alamain had succeeded in capturing Robert de Ferrers3, the Earl of Derby at Chesterfield, Kenilworth Castle still resisted the best efforts of the besiegers and another group of rebels under the leadership of John d'Eyvill had established themselves at the Isle of Ely.

Under the urgings of Ottobuono Fiecci, Henry III called a Parliament to meet at Kenilworth which, on the 31 August, constituted a committee of twelve4 to establish a settlement to the war. The end result was the Dictum of Kenilworth, announced on the 31st October 1266 according to which, amongst other things, the rebels were permitted to but back their land on a sliding scale of up to seven times its annual value, depending on their degree of involvement in the revolt.

This seems to have been sufficient to induce the final surrender of Kenilworth Castle on the 14th December, but did not entirely satisfy those rebels under the leadership of John d'Eyvill that still held out at the Isle of Ely. It was then that Gilbert the Red decided to intervene; gathering his own private army he marched to Southwark where he camped on the 8th April 1267, and on the following day was welcomed into London. John d'Eyvill slipped away from Ely to join him and for two months London was outside the king's control once more.

This might well have been the signal for the resumption of the war, but Ottobuono Fiecci persuaded the king to take a softer line. John d'Eyvill and the remaining rebels excepted a deal whereby they received immediate possession of their lands together with financial assistance (from a tax on the clergy) towards the cost of redeeming their lands.

It was therefore not until September 1267 that the war was finally over; in the following November a great council met at Marlborough and issued the Statute of Marlborough, under which Henry III swore to uphold Magna Carta and which even adopted some of the provisions previously included by the baronial opposition in their demands. By this means reconciliation was achieved and the kingdom brought to peace once more.


1 In the marshes of the Trent valley.

2 These were the Bishops of London, Lincoln, Winchester and Chichester, the fifth the Bishop of Worcester died in February 1266 before the process could be completed and hence escaped punishment.

3 Robert de Ferrers had been arrested before Evesham and imprisoned in the Tower of London; he was then released in December 1265 only to rebel once more.

4 Comprising four bishops, two earls, and six other barons.


  • Maurice Powicke The Thirteenth Century (OUP, 1962)
  • Charles Arnold Baker The Companion to British History (Longcross Press, 1996)
  • Alexander Rose Kings in the North (Phoenix, 2003)

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