I'm reading The Plantagenets by Dan Jones. It's a great read. The book spends a lot of time discussing the English barons, inducing their forcing King John to sign the Magna Carta; their ability to exact concessions in exchange for tax revenue from Henry III, Edward I, and Edward III; their turning Henry III into a puppet of the barons; etc., etc. Basically, the groundwork for what's now Parliament.
Here's what I just don't understand. Before John, it seems like the last king had absolute authority - what he said was the final law. The barons had to bend to the king's will.
How did this change? How did the barons get the power to make these demands on a supposedly sovereign king? Why couldn't these kings just sack the barons, take their land, kill them, etc.?
Any insight is appreciated!!
Because in Medieval England the political system was that of a feudal system. This meant that the important barons all owned land, castles and had armies in their own right. While in theory the king had despotic power and a provision from god to rule, in reality he is constrained by the power of the crown vice-verse the power of the nobility. There's also the matter that there has always being a sort of implicit rule of law concerning the nobility, often associated with the idea of a higher power than the king (i.e Christianity and the Catholic Church), which in practice meant that arbitrary execution of the nobility was considered to be outside the norm of Medieval monarchies.
So unlike in, say, China or the Ottoman Empire, where power came from being part of the emperor/Sultan's bureaucracy and thus even the highest ranking nobles could be executed with little resistance. Feudal societies had decentralized military power and thus an alliance of barons had armies which could challenge that of the crown. You could try to fight your own vassals (and this happened all the time), it's just that the crown don't win absolute victories all that often in this time period.