Destroy it to make room for your own with Cannon Tower on either side. Send a Knight westward to lure enemy troops toward your new position. Once you have whittled down enemy forces in this manner move the Knights and Ballista westward. Use the Knights to destroy the advancing troops and the Ballista to assault the enemy Towers. All the while reinforce your attacking army with new Knights and new Ballista from your new Barracks.
Victory is only a matter of time.
Land immediately and make your way southward, leaving the Peasants behind. Soon you will approach a pair of fortified Catapults but lucky for you they are unmanned. Kill the guards and make them your own. Take the Catapults farther south and destroy the enemy towers with their own war machines. Now bring in your Peasants and Transports and ferry your men across the river.