Important things- the number of armies you may have is limited by a system akin to "fame" in S2TW- that'll make the "forced march" reallyQuoted from Spoonska of Reddit:
Regions
Regions makeup provinces. 2-4 regions per province
You can construct buildings, raise armies, recruit agents and manage happiness and taxes for each one.
Regions in a province can be owned by individual factions, and can be taken as normal
When the settlement of a region is attack it proceeds as a normal battle.Provinces
Provinces are groupings of between 2 and 4 regions
If you own the whole province then you can pass edicts which provide various bonuses for the province
All the construction options for a province can be managed from a single screen
Happiness is also on a province level for a faction
1 region per province is the Capital
Has more building slots than the other regions
Has a "Siege" map to go with it. Can only be taken by a siege attack.
Both province capitals and minor settlements have garrisons that will defend them if they are attacked.Army & Generals
You cannot have an army without a general
Max of 20 units in an army. A navy also requires a general
If an army loses its General a new one can be appointed straight away
There is a limit to the number of armies you can have at any one time. That number is tied to your factions power. (Works similar to the fame system in Shogun 2)
You raise an army from a settlement, and then you have to appoint a general to lead it
Settlements no longer have a recruitment slot
You recruit by selecting the army not the settlement.
When recruiting your army will enter muster mode and it cannot move in this stance
Your army can be named and you can change its emblem
Generals still have skills and traits
Armies now have a raid stance. This reduces their upkeep
If they are in enemy territory it also gives some money as income, if it is done in friendly territory it additionally causes unhappiness
Forced march stance is a great way to move around the campaign map quickly. It gives a large bonus to movement distance, but the army cannot attack that turn and if it is attacked the units in it will suffer a morale penalty
And I shall go Softly into the Night Taking my Dreams As will You