Zāl Dastān
Dreamer
Two things are absolutely imperative here: power projection and national identity.
First, if the central government lacks the capacity to enforce its rule, the society will collapse in short order. What's to stop one of the constituent cities from rebelling? Usually military forces, but then territorial extent and logistics come into play. How big is the realm? If it is large, then an infrastructure at or equivalent to Rome or Persia must be present. If not, you can get away with something more medieval. The easier it is for the core to keep the periphery in line, the more stable the civilization. Facilitators are things like professional military forces (or warrior castes), roads, postal services (the faster the gov't knows about a rebellion the faster they can respond, and spy networks. Conversely, road blocks might be things like feudal armies levies (longer to assemble and therefore to respond), a weak or illegitimate central government, or social tensions within the country as a whole or individual city states.
tl;dr: If force capacity is insufficient, territory will shrink either through secession or foreign conquest.
Secondly there is what Ibn Khaldun calls asabiyyah, 'group feeling'. To put it simply, asabiyyah is the degree to which the people and factions which constitute a country (or any organization) acknowledge the authority of said central authority. If group feeling/national identity falls below a certain threshold, the country begins to suffer from a host of problems. Professional armies struggle to find recruits. Feudal lords fail to answer the call of their king. Crime increases and so does internal corruption. This effect more often than not self-perpetuates until ultimately the core is no longer able to keep the system together and at last collapses, either to internal unrest or external pressure. Common religion/civil philosophies, shared tradition, quality of life, and public splendor are boons to group feeling; sectarian tension, corruption, government weakness, and crumbling infrastructure hamper it.
tl;dr: A system stands only so long as people identify with it and see it as legitimate.
Hope this helps!
BTW, If you're interested in more of Ibn Khaldun's stuff, look into the his masterpiece the Muqaddimmah. Great stuff IMHO.
First, if the central government lacks the capacity to enforce its rule, the society will collapse in short order. What's to stop one of the constituent cities from rebelling? Usually military forces, but then territorial extent and logistics come into play. How big is the realm? If it is large, then an infrastructure at or equivalent to Rome or Persia must be present. If not, you can get away with something more medieval. The easier it is for the core to keep the periphery in line, the more stable the civilization. Facilitators are things like professional military forces (or warrior castes), roads, postal services (the faster the gov't knows about a rebellion the faster they can respond, and spy networks. Conversely, road blocks might be things like feudal armies levies (longer to assemble and therefore to respond), a weak or illegitimate central government, or social tensions within the country as a whole or individual city states.
tl;dr: If force capacity is insufficient, territory will shrink either through secession or foreign conquest.
Secondly there is what Ibn Khaldun calls asabiyyah, 'group feeling'. To put it simply, asabiyyah is the degree to which the people and factions which constitute a country (or any organization) acknowledge the authority of said central authority. If group feeling/national identity falls below a certain threshold, the country begins to suffer from a host of problems. Professional armies struggle to find recruits. Feudal lords fail to answer the call of their king. Crime increases and so does internal corruption. This effect more often than not self-perpetuates until ultimately the core is no longer able to keep the system together and at last collapses, either to internal unrest or external pressure. Common religion/civil philosophies, shared tradition, quality of life, and public splendor are boons to group feeling; sectarian tension, corruption, government weakness, and crumbling infrastructure hamper it.
tl;dr: A system stands only so long as people identify with it and see it as legitimate.
Hope this helps!
BTW, If you're interested in more of Ibn Khaldun's stuff, look into the his masterpiece the Muqaddimmah. Great stuff IMHO.