John was always in trouble with someone. The fourth son of Henry II and Eleanor of Aquitane, he was ineligible to inherit land (hence his nickname "Lackland"). Because he inherited no land, he was always conniving to gain land by other means. What he actually accomplished, however, was just the opposite. When he finally became king in his own right, after Richard died, he even lost English holdings in France.
For much of his reign, John was preoccupied in regaining those lost French territories. To pay for his battles, he increased taxes on the landed barons. Had the king been a winning leader, the nobility may have grudgingly dealt with ever-increasing taxes. But John was no winner. He continued to lose ground to the French.
Finally, the English barons revolted against the high taxes and captured London in May of 1215. They issued their terms of rapprochement: The monarch would be forced to
sign a charter giving legal rights to the barons and creating obligations on the part of the crown.
But why should the king agree to such terms? Didn’t John think (as nearly all monarchs did) that he had absolute authority? Didn’t John - the king - believe in the "divine right of kings?"