What are the conditions that must apply for balance of power to be stable?
Large number of essential actors "great powers" to make coalition formations and dissolution
The central decision makers in the essential actors must have the freedom to arrange alliances (coalitions) to deter aggression, eventually to dissolve those alliances, prevent wars of annihilation and so on.
The essential actors must share certain values. Above all, they must accept the territorial status quo.
Weapons technology must be compatible with the rules of the system: military mobilization must be slow to occur and it must be difficult to annihilate defeated countries (so they eventually can reenter the system)