This question would be for a 4x turn based strategy video game.
I have been meditating on the time consumed each turn and the space covered by the battle map.
There will be 2 maps, the strategic map and the area map for war.
The strategic map is very simple: a 6x12 hex map that covers the whole world. Half the hex are land and water. Which creates 36 space the player can build their civilisation on.
On each of those hexes, a war can occur. Now considering the amount of hex on the world, the world map hexes covers a lot of land. On that scale, USA would be made of 1 or 2 hexes.
A game turn takes 1 year
For the area map I was thinking something similar to Romance of the 3 kingdoms 2 (R3K2)
or something like wizard king
Wizard kings seems to make more sense due to the scale of the map.
Anyway, R3K2 has interesting combat resolution where you can move around, try to surround your ennemy, lure them into trap, send the field on fire, etc. Which means that combats are made of small skirmishes and maneuvering until one side wins.
Now the problem is that in R3K2, battles last 1 month which makes such maneuvering logical. But it my game, the time scale will be 1 year. Which means that each combat turn will be something like 1 week. But in 1 week, a lot of things can happen. In fact entire army unit can be decimated within a week. So it cannot be a game of maneuvering and skirmishes.
So how can you possibly resolve large scale battle over a long period of time?
It's possible that when 2 units meet on the battle map, one of them will emmerge victorious immediately. Some soldiers might survive, but they will lose any position they were defending. As for the maneuvering, it will be more a matter of beign in range or not in range of your ennemy to engage him. You will probably need to move from city to city, not sure if you could hold on in the field indefinitely. So it's more a game of connection where you should which army should fight who.
I am not sure if there are any games that deals with battles of that scale. I know that "field commander Napoleon" as 3 different scale of map (europe as whole beign the 1st scale). I could get inspiration from there.
Then the tactical strategy on the map will be to determine who is in range to fight who. Who is in range to support, etc. Then when 2 army engage each other, they go to the troop muncher below
Then I was thinking is using a system like the GURPS RPG. Both sides sum up all their factors ( troop types, ratio, terrain, morale, etc) then make 1 roll and decides the results. The results indicates winners, casualties on each side and some other variables.
Now the question is: would the tactical movement on a map still be required and interesting. What values does it add? Because I could already put all the soldiers on the map in the troop muncher.