Henry III was an unpopular monarch due to his autocratic style, displays of favouritism and his refusal to negotiate with his barons. The barons eventually imposed a constitutional reform known as the Provisions of Oxford upon Henry that called for a thrice-yearly meeting led by Simon de Montfort to discuss matters of government. Henry sought to escape the restrictions of the provisions and applied to Louis IX of France to arbitrate in the dispute. Louis agreed with Henry and annulled the provisions. Montfort was angered by this and rebelled against the King along with other barons in the Second Barons' War.
The war was not initially openly fought, each side toured the country to raise support for their army. A series of massacres of Jews in Worcester, London, Canterbury and other cities were conducted by Montfort's allies.
By May the King's force had reached Lewes where they intended to halt for a while to allow reinforcements to reach them. The King encamped at St. Pancras Priory with a force of infantry, but his son, Prince Edward (later King Edward I), commanded the cavalry at Lewes Castle 500 yards (460 m) to the north. De Montfort approached the King with the intention of negotiating a truce or failing that to draw him into open battle. The King rejected the negotiations and de Montfort moved his men from Fletching to Offham Hill, a mile to the north-west of Lewes, in a night march that surprised the royalist forces.