King Louis IX of France issued the Mise of Amiens, a settlement between King Henry III of England and barons led by Simon de Montfort heavily favouring the former, which later led to the Second Barons' War.

Louis IX, also known as Saint Louis, was King of France from 1226 until his death in 1270. He is widely recognized as the most distinguished of the Direct Capetians. Following the death of his father, Louis VIII, he was crowned in Reims at the age of 12. His mother, Blanche of Castile, effectively ruled the kingdom as regent until he came of age, and continued to serve as his trusted adviser until her death. During his formative years, Blanche successfully confronted rebellious vassals and championed the Capetian cause in the Albigensian Crusade, which had been ongoing for the past two decades.

The Mise of Amiens was a settlement given by King Louis IX of France on 23 January 1264 in the conflict between King Henry III of England and his rebellious barons, led by Simon de Montfort. Louis' one-sided decision for King Henry led directly to the hostilities of the Second Barons' War.

Henry III, also known as Henry of Winchester, was King of England, Lord of Ireland and Duke of Aquitaine from 1216 until his death in 1272. The son of John, King of England, and Isabella of Angoulême, Henry acceded to the throne when he was only nine in the middle of the First Barons' War. Cardinal Guala Bicchieri declared the war against the rebel barons to be a religious crusade and Henry's forces, led by William Marshal, defeated the rebels at the battles of Lincoln and Sandwich in 1217. Henry promised to abide by the Great Charter of 1225, a later version of Magna Carta (1215), which limited royal power and protected the rights of the major barons. Henry's early reign was dominated first by William Marshal, and after his death in 1219 by the magnate Hubert de Burgh, Earl of Kent. In 1230 the King attempted to reconquer the provinces of France that had once belonged to his father, but the invasion was a debacle. A revolt led by William Marshal's son Richard broke out in 1232, ending in a peace settlement negotiated by the Catholic Church.