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The Road to Civil War: Henry III, Simon de Montfort, and the Mise of Amiens (1264)

By 1264, King Henry III of England found his reign deeply troubled by mounting disputes with his nobility, culminating in civil war. The conflict, later known as the Second Barons' War (1264–1267), stemmed from political favoritism, financial mismanagement, and the king’s autocratic style of rule.

Sources of Baronial Discontent

Several key factors fueled the nobility’s opposition to Henry III:

1. Foreign Influence at Court

   • Henry’s Savoyard relatives (connected through his wife, Eleanor of Provence) and his half-brothers from Poitou, the Lusignans, held excessive power and influence in the royal court.
   • The native English nobility resented the preferential treatment of these foreign-born favorites, leading to widespread baronial discontent.

2. The Costly Sicilian Campaign

   • In 1254, Henry accepted Pope Innocent IV’s offer of the Kingdom of Sicily for his younger son, Edmund, requiring him to finance a war against the ruling Hohenstaufen dynasty.
   • This military endeavor was ruinously expensive, deepening Henry’s financial difficulties and further angering the barons, who saw it as a wasteful and reckless policy.

3. The Personal Conflict with Simon de Montfort

   • Initially a trusted ally, Simon de Montfort, Earl of Leicester, married Henry’s sister, Eleanor, in 1238. However, their relationship deteriorated, leading to Montfort’s emergence as the leader of the baronial opposition.
   • Alongside Richard de Clare, Earl of Gloucester, Montfort became a central figure in the movement to limit royal authority.

The Provisions of Oxford and the First Reforms

• In 1258, Henry was forced to accept the Provisions of Oxford, surrendering much of his royal authority to a council of barons.
• The reforms were expanded in 1259 with the Provisions of Westminster, strengthening baronial control over government.
• Even Prince Edward (future Edward I) initially sided with Montfort and the reformers, although he later returned to his father’s side.

Henry’s Attempt to Reclaim Power (1261–1263)

• In 1261, Henry III secured a papal annulment of the Provisions of Oxford, regaining control of the government.
• Over the next two years, his failure to reconcile with Montfort and his alienation of Gilbert de Clare (son of the Earl of Gloucester) further destabilized the situation.
• In April 1263, Montfort returned from exile in France, reigniting the baronial reform movement.
• By July 16, 1263, Henry was trapped in the Tower of London and forced to once again accept the provisions.

Prince Edward’s Counteroffensive and the Arbitration Appeal

• In October 1263, Prince Edward, now firmly aligned with his father, recaptured Windsor Castle, breaking up Montfort’s alliance.
• With the baronial movement weakened, both sides agreed to submit their dispute to the arbitration of King Louis IX of France.

The Mise of Amiens (January 1264)

• On December 28, 1263, Henry III traveled to France to present his case to Louis IX at Amiens.
• Montfort, prevented from attending by an accident, was represented by Peter de Montfort and other baronial delegates.
• Henry argued that:
  • The barons had violated the royal prerogative by denying him control over ministerial appointments.
  • They had destroyed royal castles and pillaged royal lands.
  • He was owed compensation totaling £300,000 and 200,000 marks.
• Henry also cited the papal annulment of the Provisions, asking Louis IX to release him from observing them.

Louis IX’s Verdict and the Renewed War

• In January 1264, Louis IX issued his judgment, known as the Mise of Amiens, in which he:
  • Ruled entirely in favor of Henry III.
  • Declared the Provisions of Oxford invalid, restoring full royal authority.
  • Condemned the baronial opposition.

The barons, refusing to accept the ruling, renewed their rebellion, leading directly to the Second Barons' War (1264–1267).

Conclusion: The Inevitability of Conflict

The Mise of Amiens was meant to resolve the dispute, but instead, it triggered a final confrontation. By siding entirely with Henry III, Louis IX failed to address the deep-rooted grievances of the barons, making further conflict inevitable. Within four months, open war had broken out, culminating in the Battle of Lewes (May 1264), where Montfort captured Henry III and Prince Edward, temporarily taking control of England.

The Normans had begun to make incursions into Wales, pushing westward from their bases in recently occupied England from the late 1060s onward, their advance marked by the construction of castles and the creation of regional lordships.

The task of subduing the region of Glamorgan had been given to the earls of Gloucester in 1093; efforts continued throughout the twelfth and early thirteenth centuries, accompanied by extensive fighting between the Anglo-Norman lords and local Welsh rulers.

The powerful de Clare family had acquired the earldom in 1217 and continued to attempt to conquer the whole of the Glamorgan region.

Gilbert de Clare was born at Christchurch, Hampshire, the son of Richard de Clare, Earl of Hertford and Gloucester, and of Maud de Lacy, Countess of Lincoln, daughter of John de Lacy and Margaret de Quincy.

Gilbert, also known as "Red Gilbert" because of the color of his hair, had inherited his father's estates in 1262, and from 1263had assumed the titles, including Lord of Glamorgan.

Being under age at his father's death, he had been made a ward of Humphrey de Bohun, Second Earl of Hereford.

Opposing him in Glamorgan is the native Welsh prince Llywelyn the Last, who had taken advantage of the chaos of the civil war in England between Henry III and rebel barons during the 1260s to expand his power across the region.

Simon de Montfort had returned from France to England in 1263, at the invitation of the barons who were now convinced of the king's hostility to all reform and raised a rebellion with the avowed object of restoring the form of government which the Provisions had ordained.

Henry had quickly given in and allowed Montfort to take control of the council.

His son Edward, however, had begun using patronage and bribes to win over many of the barons.

Their disruption of parliament in October had led to a renewal of hostilities, which saw the royalists able to trap Simon in London.

With few other options available, Montfort had agreed to allow Louis IX of France to arbitrate their dispute.

Montfort had been prevented from presenting his case to Louis directly on account of a broken leg, but little suspected that the king of France, known for his innate sense of justice, would in January 1264 completely annul the Provisions in his Mise of Amiens.

The settlement had not presented a solution to the conflict, but rather a recipe for further problems.

The one-sided decision for the king and against the barons leaves Montfort with little choice but armed rebellion.

Hostilities star already in February, when Montfort's sons, Henry and another Simon, attack the possessions of Roger Mortimer in the Marches.

Henry summons the feudal army, and the royal forces win an important victory at Northampton, where the younger Simon is captured.

The twenty-year-old de Clare in April 1264 leads an expulsion—some sources call it a massacre—of the Jews at Canterbury, as Simon de Montfort had done in 1231 in Leicester.

Gilbert de Clare’s castles of Kingston and …

…Tonbridge are taken by King Henry III.

The King allows de Clare's Countess Alice de Lusignan, who is in the latter, to go free, however, because she is his niece, but de Clare and de Montfort are on May 12 denounced as traitors.

Simon de Montfort knights Gilbert de Clare and his brother Thomas two days later, on May 14, just before the Battle of Lewes.

Montfort is still in control of London, as Henry regains control over Kent and Sussex.

Montfort marches out of London to negotiate, but the terms—involving maintaining the provisions —are rejected by the king.

The only option remaining is to fight.

Gilbert de Clare commands the central division of the baronial army, which forms up on the Downs west of Lewes.

When Prince Edward leaves the field in pursuit of Montfort's routed left wing, the King and Richard of Cornwall, Henry's brother and the titular king of Germany, are thrown back to the town.

Henry takes refuge in the Priory of St. Pancras, and Gilbert accepts the surrender of the Earl of Cornwall, who had hidden in a windmill.

In spite of inferior numbers, the baronial force have won a spectacular victory, capturing the king, Lord Edward, and the Earl of Cornwall.

Montfort and de Clare are now supreme and de Montfort in effect de facto King of England.

Montfort uses his victory to set up a government based on the provisions first established in 1258 at Oxford.

Henry retains the title and authority of king, but all decisions and approval now rests with his council, led by Montfort and subject to consultation with parliament.

Gilbert and his associates had been excommunicated by Pope Clement IV on October 20, 1264, and his lands placed under an interdict.

The Earl is proclaimed to be a rebel in the following month, by which time they had obtained possession of Gloucester and Bristol.

However at this point he changes sides as he falls out with de Montfort and the Earl, in order to prevent de Montfort's escape, destroys ships at the port of Bristol and …

…the bridge over the River Severn at Gloucester.