Within my setting, there is a large empire which includes all of civilized humanity, within a late medieval setting. There are no notable external forces, so any and all conflict has always been from within the empire.
Previously, the empire was well respected and honoured by all, each of the many kingdoms swore fealty to the emperor, and presented to the emperor a portion of their armies as well as their money.
However, that all changed when there was a succession dispute, however, the true rightful empress was dethroned and exiled. Now, an emperor, who was the deposed empress's sibling, is in control of the empire.
Now for the question, how do I allow the kings to fight each other, while still swearing fealty to the empire, AND make it so that the emperor has little to no martial power?
Things to note:
- Late-medieval tech levels all around
- Low powered magic is common, but high powered magic is very rare
- There are various races of varying sizes and capabilities within the empire, all of them are political equals to one another and are full members of society.
- Humans do not outnumber the rest of the races. Humans will make up about 25% of the population, but each other race will then be about 3-6% each.
- The emperor is human.
- The many races are more nationalistic than racist.
- Gender-based race are in full swing, when a male X marries a female Y, all boys are X and all girls are Y.
- If it was not obvious before, feudalism is in full swing here. A majority of any landed ruler's troops and money would have to come from his/her vassals
- As for gender succession, it is going to be absolute primogeniture, which is to say, the oldest child inherits, male or female. Also matrilineal marriage is very common, when the female is of nobler blood or higher rank.
PS: Most of these things are based from me playing crusader kings II, so feel free to correct me where needed. Sorry in advance.
EDIT 1: Do note that the scope of the empire has slightly shrunk from all of humanity to just all civilized humanity. This means that there are barbarians and the like outside the empire.