I assume we'll all be posting turns at once?
Yes. Turns are assumed to occur simultaneously. In the event of conflicting military orders, like intercepting an army, I'll determine what happens based on both common sense "what should happen" and roll a dice, biased towards an outcome favorable to whoever has the strategically fastest army.
I'm thinking that I might want plants, trolls, and standard elf cavalry to all move at the same base strategic speed, modifying it more by heavy foot men-at-arms or having army logistics wagons.
But it's also tempting to make the plants and trolls research ways to move faster. I'll have to think about this.What happens when we're potentially attacking each other? Like if Player A has the order "Attack B's army on that hill" while B has "Retreat off the hill back toward the city". Is there a unified resolution in that case?
If they start the turn next to each other, there would likely be a lower intensity battle while B plays a fighting retreat.
If Player A is further away, then player B should be able to get away without making contact, unless A has strategically faster units who can reasonably slow B down and I think A wants to press the attack (IE, Attack That Army vs Capture That Hill).
Edit: Before battle begins, players with generals will get the chance to decide on their tactics through PM. Players with explorers might, while players with neither are unlikely to get a special tactics decision round and should be careful to give good orders beforehand.
Regarding strategic speed, I think I'll have troll/plant light infantry (eg, spearmen with just spears, archers with just bows) move at the same strategic speed as normal light/medium infantry (eg, spearmen with leather armor and wooden shields, archers with leather armor), while troll/plant medium and heavy infantry (eg, spearmen with metal armor, archers with spears) move at the same strategic speed as normal heavy infantry.
In general, light cavalry should be the only cavalry to get a strategic speed boost.