Create the most medievally awesome army on the battlefield, then squash your foes to oblivion in Feudal Wars, an IO strategy game.
You start with but a single castle. Use the knights that spawn from it to capture more territory and increase the enemies you can spawn.
The game is a rock-paper-scissors format. If your enemy is creating a lot of calvary (the guys on horses) then create polearm units from barracks.
Also, the more castles you have, the bigger your army can be. Each one increases the size by twenty. So five castles equate to a 100-man army.