The following numbers is a recommended minimum for EACH of the cities you want to defend. As you are building up the troops, make sure you have a layer of troops as much as you can. You are harder to defeat if you are layered!
300k warriors
200k scouts/archers
50k pike/swords
and FULL WALLS
300k warriors
200k scouts/archers
50k pike/swords
and FULL WALLS