What events led English barons to rebel against King John in 1215?

The rebellion against King John in 1215 was driven by long-standing grievances regarding his oppressive rule, financial exactions, and military failures.

Key factors leading to the uprising included:

• Financial Oppression: John imposed heavy taxes, such as the 1207 "13th," and levied massive reliefs (inheritance duties) on barons, which were viewed as arbitrary and excessive.1
• Military Failure: John’s costly and unsuccessful attempts to reclaim Normandy culminated in the defeat of his allies at the Battle of Bouvines in 1214. His insistence on military service in Poitou was deeply unpopular, particularly among northern barons.21
• Abuse of Power: Unlike his predecessors, John spent most of his time in England, making his disregard for established law and feudal custom feel more immediate and intrusive.1

By the spring of 1215, these tensions coalesced into a widespread movement to ensure the king remained subject to the law. This led to the meeting at Runnymede, where the Articles of the Barons formed the basis for the Magna Carta.21