The Magna Carta barons were a varied group that sat near the top of the feudal hierarchy. This included men who had been granted baronies, and a handful who held earldoms. Their possessions might have included castles, villages, farmland, or sections of forest. Many would have wielded immense power over the lands they controlled and their vassals, and may have functioned as mini-Kings. They would have had their own private armies, their own court and officials, and certainly their own dynasties.
There were many barons in England during King John’s time. One historian has suggested that there were about twelve earls in England, and between 100 and 150 barons. Not all of them were involved in the rebellion against him in 1215. Some barons—for example, the Earl of Pembroke, William Marshal the elder—stayed loyal to King John. Others refused to take sides altogether. But enough of them rebelled against King John in 1215 to pose a serious threat to his authority.
On 5 May 1215, a powerful group of English barons rejected the King and decided to take up arms and wage war against him. Their rebellion would ultimately force the King to agree to the terms of the Magna Carta. But what caused the barons to rebel in the first place? What compelled them to wage war against their own King?
Some of the barons had personal reasons to want to go to war with John. Robert FitzWalter was one of them. According to some accounts, he claimed that John had attempted to seduce his daughter and have his then-son-in-law, Geoffrey de Mandeville, executed. Geoffrey was another with a personal reason to revolt against King John. After his wife—and Robert’s daughter—Maud died, King John forced Geoffrey to marry his own ex-wife Isabella of Gloucester, and to make an absurd payment of 20,000 marks to the royal treasury to get permission for their marriage.
But the baronial revolt was propelled by more than just personal grudges. Rather, the rebel barons formed an alliance because they supported a common cause: they wanted to stop him from arbitrarily taking their money and land.
Like his brother Richard I before him, King John waged war against the King of France, Philip Augustus. Within a few years of becoming King, John had lost most of his French lands to Philip—including Normandy. But John refused to give up France for good. Between 1204 and 1214, he was busied raising forces to fight in France and reconquer the lost territories.
But war is expensive. It requires a lot of money. When John’s elder brother King Richard I ‘the Lionheart’ had died, he had left the royal treasury depleted. This meant the only way that John could raise funds for the war—and quickly—was to take money from his subjects.
Before too long, the King’s demands for money became so great that many of the barons could no longer pay what was asked of them. Many were forced into his debt. To make matters worse, the King’s wars went badly. In 1214, King John left with an army to invade France. After a few months, he returned to England completely defeated. All that money had been raised and spent for nothing.
John’s arbitrary demands for money—paired with his unsuccessful military campaigns—was a major factor that compelled many earls, barons, knights, and other landowners from across England to rebel against him in 1215.