I would make it so there are three phases:
Orders Phase
[Time Skip]
Battle Phase
[Time Skip]
Development Phase
On the Orders Phase each Commander (player) will imply via IC how they wish to divide their armies amongst their generals (minor player-characters), where they wish for them to march to, etc. You can only post once here. Once everyone has posted I will post with a time-skip that details the results of everything you said in the Orders Phase (the success/problematic arrival of an army in a region, for example).
Next is the Battle Phase, where any conflicts will be settled. If any two armies meet up in the same region, a battle could ensue. If both Commanders/Generals decide NOT to attack, nothing happens. Battles will play similarly to how they do in Rise of Domrius, but I won't go into detail just yet. If an army moved into an unoccupied region, the player can explain what's going on there, such as razing a village, trying to take control of it, etc. There is no limit to the number of times you can post here; the phase ends when all conflicts all settled.
Next is the Development Phase, where the players can take time to develop their character stories, or collaborate with other players to build character development and relationships. This phase is optional and there is no limit on posts, but there wouldbe a deadline.
Then we start over at the Orders Phase, and so on and so forth.
EDIT: I will name each session (a session is all 3 phases together) afterwards accordingly. For example, if several armies waged a large battle in Kawajia, that session would be "The Battle of Kawajia". "The Fall of Hakutsune Clan", "The Execution of Jawa Marlake", "Gathering of Three Armies," etc.