Back to Warcraft: Orcs and Humans
Take your entire force east and then south across the bridge. Continue to the east until you find the prison where your Peasants are being held. Make sure you clear out the Spearmen behind the prison otherwise they will kill the Peasants before they can run away.
Break the walls and send the Peasants back to the town so they can start gathering resources. Leave some of your army on your side of the bridge. This is the only way to cross the river so if you hold it the Orcs won’t be able to attack your town.
Build up your town and train a handful of Knights, Archers and Catapults. Slowly move down towards the Orc outpost and take out anything that gets in your way. Once the last structure has fallen and the last orc slain the mission will be complete.