John orders a scutage of 3 marks per knight's fee in May 1214 - an extortionate fee. The barons urged John to reissue Henry I's Coronation Charter in November but he postponed any discussion on the matter.
The barons meet at Christmas 1214. That January, they demand John follow The Unknown Charter of Liberties. It covered feudal reliefs, wardship, marriage, military service, forest law, and scutage (capped at 1 mark).
We refused to pay scutage (and did plot to kill him).
He made me marry Isabella of Gloucester for 20,000 marks!
Refusing, both John and the barons prepare for war with Marshal and Langton as John's negotiators. He also took the cross, gaining Innocent III's support against the barons who he refused to meet in Easter 1215.
The barons revolt - Robert FitzWalter is their leader (Marshal of the Army of God). In response, John sends his sheriffs to seize land. The barons fail to take Northampton but convince William de Beaumont to join them, taking Bedford.
With help of rebels, the barons take London, seizing John's supporters and the treasury at Westminster. Like that, the rebellion changed - earls joined the barons (like Hertford and Norfolk). Some remained loyal - Marshal, Surrey, Derby, Arundel.
Assembling at Runnymede on the River Thames, the barons list their demands in the Articles of the Barons. There were 49, focusing on scutage and reliefs (baronial matters), but also trade, local government, and fish weirs. After negotiation, Magna Carta was drawn up and sealed