How to stop the King of Armies to coup the other Kings?

Question

In the world I am building the main geopolitical power is a nation ruled by seven kings, each having their own area of authority. One of them rules over the nation's armies and there should be a reason why this king doesn't use the military to overthrow the other kings and become an absolute monarch.

The world is a classic fantasy setting, but more civilized than the usual. Magic is rare enough that it can't be used for agriculture and the like, but common enough that you would expect any important figure to have access to magic (because they can use it or because they know someone who can). Gods don't intervene in mortal business but their clergy can.

The nation in question is old and grows more and more decadent. At the beginning of the story there is no serious external threat and it has been like that for almost a century. Each throne has its own succession rules (some are elected, some inherited, some have to change hands after a set amount of time, some last until death, etc), and different things they administer (communications, food, minting, etc)

What could be a good explanation for why the king that rules over armies haven't yet overthrown the other kings? Ideally I would like to avoid magical artifacts or powerful rituals.

Answer 1

Several elements may come into play:

The king is under the law because it is the law that makes him king.

Tell the soldiers to overthrow the other kings, and they get to throw you into jail and inform the other kings of your treason. Even in the most cynical of countries, soldiers will do that as long as the reward is greater than obeying you -- and if you stage a coup, unrest and civil war are likely to follow, endangering their lives.

Logistic failures

Other kings control aspect that your armies would need. Food, for instance, or weaponry. Foraging for food will turn the commoners against you, and weapons are infeasible.

You need them

The other kings control the boring bureaucracy to keep the other parts of the empire intact. Overthrow them and panicking bureaucrats can ruin everything by running away from the (non-existent) danger.

Besides, without them, you would need to take over their role

Multiply targets

As a lone king, you are the target of every malcontent. Splitting it up lets you know that others will be targetted. Indeed, you can shift blame to other kings if you do it adroitly.

Answer 2

A couple of reasons

Firstly one of the other Kings is the 'King of Spies.' And he has eyes and ears everywhere, including the army since his remit covers both external and domestic threats to the security of the realm.

Secondly another King is the 'King of Gold'. He controls the royal treasury and is responsible (with input from all the other kings) for the collection of taxes and the allocation of financial resources across the government, including for the army. And all the Kings not just the Army have to wrestle for their share of the pie.

The third reason is related to the second. Since you've stated that' there is no serious external threat and it has been like that for almost a century' over time the size of the army has decreased to the point where seizing control of the entire country with the available forces would be difficult. Especially if the seven kings each took care to partially decentralize their authority across the empire so that just seizing the capital doesn't necessarily end the other kings authority and reach across other parts of realm (redundancy).

Also there's no particular reason that all the King of Armies regional officers would comply with his orders. That would require all of them to be in on the conspiracy from early on. (And that's potentially scores of senior officers!) And the more people involved the more likely it is someone will be discovered by the King of Spies agents or perhaps seek reward from the other Kings including the King or Gold in return for grassing out his co-conspirators.

Lastly each of the Kings retain their own personal Royal Guard Companies responsible for protecting that King & their families etc. While individually these guard companies are only be a fraction of the size of the Royal Army collectively, in the capital and with the aid of the city watch they balance out or perhaps even outnumber the army. This is because by default most of the army has to deployed elsewhere. And of course, at law approval is required from the other Kings before the King of Armies can station more than a set number of troops into or near the Capital.

Answer 3

They are Busy keeping the Army Busy

Similar to Ancient Rome, the main job of the King of Armies is to keep the army occupied, so the generals do not stage a coup of their own. This is especially hard in the absence of a real external threat.

The King of Armies is also aware that staging a coup against the other kings would make their generals in turn MORE likely to coup the new king. So they don't bother.