One kink in our plans, how will we prevent Berlin from just flipping back to us?
When a town wants to flip to you, you get a popup asking what to do. You can simply refuse the town and then it remains with its current owner.
What are we doing with the horse army past the choke point? Is it just pillaging for mischief/scouting or do we have an objective?
What do we want our new Barborossa to do-army I assume back at Dortmond, but fill with what?
Lanzelot, re the spices at Marathon-were you thinking of taking the city, taking/wasting then building a new city? I know we need to start conquering, but holding a town just past our funnel seems a challenge.
The Horse Army is at its current location because of the following: I had sent a stack of workers last turn to build a road towards Marathon (trebuchets can't go through swamp/jungle, they need a road). In the interturn a Greek longbow appeared on the tile where the Horse Army now is. I let the worker stack build the road, moved two trebs on that road to bombard the longbow, and then sent the Army to take it out. Then I sent two spears as protection for the Army. Next turn they will all return to the chokepoint mountain.
Barbarossa should not go back to Dortmund, too dangerous. I kept him with the stack, and he can form a new 4-longbow Army in Corinth.
You are right, I think we can't take (and hold) Marathon at the moment. But as a medium term plan we should keep it in mind. Within the next 10 turns or so, we should have 2 muskets down at the chokepoint, and then we can risk sending the 6 workers on the jungle square adjacent to the coast, let them build the road, roll all our trebs on that square and take the town next turn. With muskets we should be able to hold it. (And also the road will allow easy reinforcement.) By that time Athens should have fallen, so the walls at Marathon will no longer be there, when we attack.
(But after we take it, they will reappear, easing our defense...

)
I don't know about a horse army, but the Spear army is off to disconnect the Persians resources. Mainly Horses (cause they only got one source), then Iron.
Don't forget the saltpeter!! It's almost on the way to the horses, and at the moment it's even more important! The Persians have started to man all their towns with muskets already! I don't want them to get too many of those...