[1] Small caveat on this in that royal families held something akin to the mandate of heaven by virtue of their heredity. This mandate did not necessarily follow lineal descent and regularly transferred to siblings, family, or even close vassals that outshone than the original line.
They pretended that they did have such a divine right:
https://en.m.wikipedia.org/wiki/Divine_right_of_kings
Events like the French Revolution proved them wrong:
To be fair nobody took it that seriously before either. Cities, regions, nobles etc. were constantly trying to challenge the king and his/her authority and protect/expand their rights and privileges.
It’s just that before the French Revolution they usually just wanted to extract additional privileges from the monarch or limit his powers (or in the worst case replace). The same thing happened in the French Regime before it got slightly out of hand..
e.g. even Louis XIV constantly had to fight the courts to force through his new laws (and was almost deposed in quasi-revolution(similar to the English civil war just without the religious element) at the beginning of his reign)
Okay. Also, similarly, the Magna Carta in England.
> If you want to keep the empire unified, you need a civilian government and civilian institutions to keep the military under control.
But then you run into another classic political science problem: how do civilian institutions keep the military under control? Why can't the military simply shoot the civilians and institute a junta?