The game is built on the same feudal social and political structures as the early middle ages europe to start off with.

So armies are raised and maintained exactly as they did back then. Smal standing armies maintained by Barons, Dukes and Kings. Counts, Dukes and Kings also have their own household forces. Wealthy landed lower aristocracy and gentry arm and armour themselves. So you get a small pool of regular troops, a small pool of well equipped (but often undisciplined) knights and gentry militia. Larger towns and cities also often had their own militia that acted both as a police force, and a defence force, that at a push could be used in regular military action.

The vast bulk though are levies. So when levies are called the counts go around their towns and villages and gather up a certain percentage of able bodied men, arm and armour them. If a Duke calls their levies then each count provides an agreed upon amount of levies from their county domain. A king calls the dukes who provide an agreed amount of their levies etc. and these pool together gradually to form an army.

So the bulk of the forces are often your peasants, armed with basic gambeson or whatever armour was available and spears or bows. Your regulars, gentry and middle class levies form the better quality troops, aristocracy form your knights, other cavalry etc. or heavy foot troops.

When the conflict is over, everyone makes their way home and goes back to the job they had previously.

Maintenance for armies is generally dependent on who raised the levies or whos personal guard they are etc.

For the peasants, it is their local count. For town militia the mayor. For barony regulars, the baron (with the help of the duke). For gentry and all aristocracy they maintain themselves. Household guards are maintained by the lord's household budget.

For big campaigns the lords would work together to ensure the armies remain fed, often whoever called the conflict at the top level would take charge of payments for food and basic supplies, while each "camp" within the army maintain their own tents, horses and fighting equipment.

When the call goes out for troops towns will loose part of their NPC / family members who sign up to go fight. Instead of having 20 farmers in town now you only have 10, and not to mention all of the food they will take with them. This could cause food shortages for the rest of the town.

Basically it's most likely going to mimic real life: Notice is sent out to settlements for troops, npc/players travel to a set location as the army forms, troops are kept fed and armed, big battle scene, spoils for all survives (possible land title rewards for players), army disbands and NPCs and player go home or stay in the newly conquered.

Most players will never really know why they are fighting. Management said we are going to go fight here, so we do what we are told. Could be because the ruler deiced to oust someone for not falling in line, or because they are trying to start an uprising. Who knows who cares. There's fightn to do.

As to how and who controls the NPCs in the battle is unknown to me, but I wonder if it could be something like Starcraft for the general. Either way it's going to be interesting to see an actual big battle happen.

Just remember who you are fighting for though. If your ruler is the one starting a resistance then you might be on the loosing side against a superior force. Might be easier to "retire" the ruler of the settlement before they start a war they cannot win.

We don't yet know in detail how large-scale wars will work. We don't even know what "large-scale" means in terms of the numbers of characters, but various hints from the designers suggest that hundreds rather than thousands of characters will constitute a typical wartime army.

What we do know is that formal wars will have heavy logistical requirements, while we strongly suspect that they will have heavy command-and-control requirements. The former means that wars will be expensive in resources and require a fair amount of planning, in order to keep armies fed and supplied with anything critical that can wear out or be used up. The latter means that the action may not much resemble that of a raid in a typical MMO.

As Poldano said, the short answer is we do not yet know how thingw will work.

But we have a few elements of answer to some of the questions you ask.

• "So I was wondering exactly how warfare and militaries work" : To that one no answer yet.

• "the descriptions for duchies talk about how they are responsible for defense and military actions so are dukes the only ones who can do this?" : Yes and No :), the Duke through its duchy management UI is the only one to have access to the tools the UI provides. But anyone can build military structures, hire troops and eventually engage them in combat.

• "Also there's coups for lower nobility and aristocracy such as counties and mayorships so does that mean they too can field there own armies" : Yes as pointed above, there is nothing preventing anyone to build military structures, hire troops and use them. Any of that could locally be restrained or regulated by laws but even laws do not prevent you from doing things, breaking them only turn you into a criminal....

• "how are they maintained" : no definite answer to this one, but logic would point toward a contractual relation between who hire the troops and the soldiers, with some form of salary. Buildings, and gear are maintained as any building or gear, either by spending whatever resources and wealth necessary or replaced.

• "what requirements are there to get one?" : technically, none. But nothing appears out of thin air in COE ( at least after exposition) so whatever you do, it will only succeed if the resources and characters are available. There is also as touched earlier the subject of laws, if things are forbiden or regulated you might have to compply or risk becoming an outlaw.

So to summarize we do not know yet much about how military will work or what it implies, but we know that it wont be restricted or limited to dukes, any one with the will, and resources can build military structures, hire and equip troops and use them.